Life Cycle Planning
This page features information on planning and managing the life cycle of transportation assets. Whether you are defining, implementing, or strengthening your life cycle planning processes, you will find what you need here.
Defining Life Cycle Management
Through life cycle management, agencies employ data on asset condition, treatment options, costs, deterioration rates, replacement cycles, and other factors to determine the most cost-effective, long-term strategies for managing assets throughout their lives.
All transportation infrastructure assets have a life cycle, which includes several stages from initial construction to removal or replacement (see figure 4.1). Life cycle management is an investment approach that considers maintenance, renewal, replacement, or repair options through an asset’s service life with the intent to maximize the benefit provided by the asset at the minimum practicable cost. It employs data on asset condition, treatment options, costs, deterioration rates, replacement cycles, and other factors to evaluate trade-offs between possible investment strategies and treatment timings. Effective life cycle management requires knowledge of the agency’s strategic priorities and an understanding of the performance criteria driving investment decisions, so the right management strategy can be identified and implemented for each asset class. Aligning asset management measures with agency priorities ensures the investments made to extend asset service life provide the maximum impact to the agency’s long-term goals.
Figure 4.1 illustrates a variety of interventions that occur over an asset life cycle. The larger circles represented in the figure are service life altering, and represent a capital investment in infrastructure. Capital investments provide significant life extension, and may alter or enhance the operational nature of the asset, e.g. expand capacity, without fully replacing the asset. Maintenance (reactive, interval based and routine) activities are required throughout the life cycle to ensure the asset achieves its service life. Preservation treatments restore condition or performance to achieve service life, and may extend service life as well, but do not significantly alter the operational nature of the asset. Some agencies may capitalize investment in these preservation activities; however, regardless of the timing and character of the selected interventions, all of them are part of the life cycle management process. More (lower cost) maintenance interventions can offset the number and cost of the larger (and more costly) interventions. Balancing the right intervention, at the right time, can greatly reduce the overall investment needed for infrastructure to be reliably available for providing service.
Life cycle management can be used at both network level and at project level. At network-level, life cycle management considers the needs of an entire asset class, as well as the available funding, to determine the most appropriate life-cycle strategies. For example, analysis can establish the optimal proportions of overall investment that should be allocated to different types of interventions over the network, to minimize investment to achieve performance targets or an average condition level. At a project level, life cycle management is commonly used to develop asset-specific strategies. Project level life cycle plans provide input into the network level life cycle plans. Large bridges or other distinct network components are often planned and managed in this manner.
Life Cycle Cost Analysis (LCCA) is an engineering-economics approach that can be used to quantify the differential costs of alternative design approaches. Network level life cycle management, while a more holistic process that manages every stage of an asset’s life, may employ LCCA or other forms of analysis to inform management decision-making. Figure 4.2 highlights some of the major differences between life cycle management and life cycle cost analysis. At the network level, LCCA can be used to understand how to best manage the network as it ages. At a project level, it is used to understand what are the most effective actions to be taken on the assets within the project scope at the time of project delivery. Both network level and project level analyses contain many aspects of engineering economic analysis, such as consideration of user benefits, user costs, and the time-value of money to identify alternatives that represent the lowest practicable life cycle cost over the analysis period to achieve the desired objectives.
Figure 4.2 Attributes of network level life cycle management and project level life cycle cost analysis
- High level.
- One asset class or subclass.
- Multiple locations.
- Looks at impacts of varied treatment timing.
- Considers future cost changes.
- Multiple asset classes.
- Single location.
- Treatment timing fixed for all options.
- Uses discount rate.
Source: Applied Pavement Technology, Inc. 2017
Decision Making Context
Life cycle management is driven by the need for owners to provide consistent service to those that use the transportation system with the resources available. Infrastructure decision making can take place at several levels within an organization, and in each case, considers different but often interrelated factors. These are illustrated in table 4.1.
Table 4.1 - TAM Decision-Making Contexts
Key Questions and Connections to Other Chapters
|Key Decisions||Setting goals and objectives.||Capital investment prioritization and scoping and Integration of maintenance and renewal strategies||Delivery of the capital program, routine maintenance, and highway-operations activities.|
|Decision Makers||Directors and managers who are asset stewards.||District and field mangers, supervisors, and staff.|
|Other Factors||Decisions and outcomes of these strategic questions help focus investment. They add value to overall performance of the transportation system by setting priorities, values, and help prioritization of investment at lower levels. Creating new assets and disposing of existing ones are strongly influenced by decisions and priorities defined at this level.|
Chapter 2 discusses these considerations in more detail, and the level of service section in this chapter discusses linking these strategic priorities
to decision-making at lower levels. Performance and target setting in Chapter 6 also discusses this linkage and how targets can be set to achieve these strategic goals.
|This Chapter focuses on these questions and on the analysis that informs their corresponding answers and decisions. Life cycle management and analysis focuses on the existing transportation system and evaluates how:||Delivering a program work, ranging from maintenance activities to capital improvements, requires a coordinated management of a large workforce. It requires processes that minimize input of resources to get the output required for desired system performance. Work management systems, efficiency
and improvement techniques and performance management focus on improving decisions at this level. These concepts are discussed in Chapter 5, 6 and 7.
Figure 4.3 Analysis of KYTC Future Costs Under Two Strategies
Source: Kentucky Transportation Cabinet Transportation Asset Management Plan, 2018.
Kentucky Transportation Cabinet (KYTC)
In the early 2000s, KYTC found that the cost of hot-mix asphalt (HMA) was increasing faster than its budget to maintain pavement conditions. In response, KYTC evaluated the feasibility of strategies that relied heavily on preventive maintenance overlays such as thin HMA overlays (< 1 inch), chip seals, cape seals, and slurry seals. KYTC found that while the costs of these treatments were substantially less than a traditional HMA overlay, their service lives were only marginally shorter. As a result, the agency began increasing the use of these treatments on its secondary system. As part of developing its risk-based TAMP in 2018, KYTC evaluated life cycle strategies, as shown in Figure 4.3 Analysis of KYTC Future Costs Under Two Strategies that expanded the use of preventive maintenance overlays to its parkway and interstate pavements. The analysis results led the agency to select a life cycle management strategy that maximizes the use of preventive maintenance overlays on secondary roads and parkways and increases their use on interstate pavements over time. As shown in Figure 4.3, this new life cycle strategy achieved conditions over the 10-year TAMP analysis period that would have cost an additional $644 million if they had continued to rely on traditional 1- to 2-inch HMA overlays. By implementing these improved strategies, KYTC has significantly reduced the risk that the infrastructure will reach an unsustainable cost to maintain in the future.
Source: KYTC Transportation Asset Management Plan, 2018. http://www.tamptemplate.org/wp-content/uploads/tamps/048_kentuckytc.pdf
Defining Asset Service and Performance Levels
Before asset performance can be managed, an agency must first define what it is seeking to achieve. In TAM, asset performance is most commonly defined in terms of asset condition or maintenance level of service. Performance may also be evaluated in terms of safety, availability, reliability, resiliency and other service attributes. Regardless of the method used to monitor performance, it should be used to inform analysis that supports decisions to help ensure that investments enable an agency to achieve its goals cost-effectively.
Establishing Desired Levels of Service
Before a whole-life strategy can be developed and implemented, an agency must determine what they seek to achieve. In many transportation agencies, the desired level of service (or asset management organizational objectives, in ISO 55000 terminology) provides the linkage between what the goals of an agency are, and what investments and interventions should take priority when managing assets. High level goals should directly influence investment choices when resource allocation decisions are made. Service levels help establish when gaps need closing to achieve a goal, and merits investment. Chapter 2 discusses ways to create linkages between goals and investment decision making.
When managing the life cycle of existing assets, performance targets are commonly established as a way to manage service levels for the transportation network. How to determine the expected level of performance may vary depending on the type of asset being managed. Level of service targets that are part of performance framework typically are a mixture of both customer focused performance measures, and technical service measures that help those responsible for the asset assess what types of interventions might be required and when. Customer focused service measures are important to road users and other stakeholders that require mobility. Travel time reliability, safety, load capacity and clearances, and lane availability are all examples of service targets that are customer focused. Condition, strength, regulatory compliance and examples of technical service attributes are commonly of greater interest to asset stewards than asset users. Both types are service level targets that are important to evaluate the efficacy, effectiveness and efficiency of a transportation system.
For pavements and bridges, and other assets managed using a condition-based approach, asset condition is commonly used to establish expected technical levels of performance, but also is relevant to customers. For example, condition is employed as a proxy in this way for pavements because it is objectively measurable, deterioration has some predictability. It is a valuable service attribute because often, user experience is also directly connected to condition as well. Potholes, rutting and roughness all reduce quality of service from a pavement. Performance measures, such as those discussed in Chapter 6, are used to establish the desired long-term performance and to set short-term targets that can be used to track progress towards the long-term objectives. For other highway assets, including those managed using interval- or time-based maintenance approaches, performance may be linked to the expected service life, the ability of the asset to fulfill its intended function, and/or other operational factors. For these other highway assets, performance targets are often established as part of a Maintenance Quality Assurance (MQA) program in terms of desired maintenance levels of service (MLOS) and integrated with operational service targets that may also be customer focused.
Risk can also be used as a measure of performance. As described in chapter 2, risk considers both the potential impact and consequence of failure. This can be particularly useful when the potential consequences of failure impact other assets or facilities. An example of how Colorado uses risk to manage rockfalls is included in section 4.3 of this chapter. Additional details on how to track risk-based performance measures is included in Chapter 6.
Establishing a desired level of performance is typically a collaborative process that considers existing conditions, available funding, expected demands on the system, policy goals and guidance, and stakeholder priorities. The desired level of performance is typically established once baseline data is available, so performance trends can be evaluated. The desired level of performance may be adjusted over time to reflect changes in agency performance, changes in asset condition, capacity, safety, resiliency and other factors.
Three types of service expectations are often used in combination to manage asset performance:
- Performance target – the level of performance beyond which additional performance gains are not desired or worth the additional cost. When performance is measured based on condition, the desired performance may describe the desired state of good repair. There may be an expected specific time frame to achieve this desired performance target.
- Current Performance – an intermediate level of performance achieved by the organization and is usually reported relative to the desired target. Target setting is described in more detail in Chapter 5.
- Minimum acceptable performance – the lowest level of performance allowed for the asset or asset class to still function as designed.
Performance expectations may be set for the road network, a road corridor, for individual assets or for a group of assets. Commonly, performance expectations are set using a combination of asset class or subclass or sub network, such as:
- Key network corridors.
- Bridges on the National Highway System.
- Interstate pavements.
- Culverts larger than 10 feet in diameter.
- Traffic signals serving more than 10,000 vehicles per day.
The nature of performance expectations can be either strategic or tactical or operational. Strategic expectations support freight movement; for example, the long-term goal of providing unrestricted flow of legal loads is supported by a performance expectation of no load-posted or restricted bridges on interstate highways. This expectation cannot be accomplished without the tactical delivery of work to address factors contributing to the physical condition of bridges. Thus, an agency may include tactical expectations to perform maintenance and repair on structural members on a routine basis or as conditions warrant. These enhancements can be also integrated with renewal and other rehabilitation interventions to help improve both tactical performance metrics, as well as achieve higher level goals and objectives. Operational improvements such as more responsive snow clearance, and better signage are all integrated treatment options to achieve the strategic objective.
Life cycle management analysis, and the decisions it supports, require service levels, performance targets and other objectives to be able to determine the optimal choices for agencies to select during resource allocation. Over an asset life cycle, a range of interventions are possible, from reactive, routine and preventative maintenance, to large investment associated with renewal, replacement, or removal. Having targets helps select the right interventions and investment option while balancing risk, service and cost.
Connecting performance measures to higher level strategic goals also supports an agency’s ability to communicate how technical measures relate to system performance as experienced by highway users and other external stakeholders, thus tying asset management outcomes to system performance. Asset management measures are often very technical. Performance indicators like bridge ratings, pavement distress measurements, and risk ratings are not commonly understood by those outside transportation agencies. However, agencies can use these technical measures to support the performance indicators that are more commonly understood and prioritized by system users and external stakeholders. Communicating system performance and the status of the road network is discussed in Chapter 2, and is illustrated in several examples below. Customer service level targets are often established for this purpose, and give users an ability to understand the quality of service they should expect on the transportation system.
Each year, the Colorado DOT must report to its legislature on the statewide highway infrastructure and the agency’s ability to meet those needs with available resources. This requirement is met through the Annual Infrastructure Deficit Report, which addresses pavements, bridges, and annual maintenance. The agency supports the annual maintenance portion of this report with its Maintenance Level of Service Measure, which rates the delivery of services in nine program areas in terms of a letter grade from A to D and F. The agency has used historic data to develop deterioration rates for each service area that estimate the resources needed to improve the maintenance level of service by a given amount over a specific time period. These estimates are summarized in the Report, which is in turn used by the Legislature and the DOT to establish the annual maintenance budget. The figure provides an example of information on MLOS in the 2016 Report. Once the targeted MLOS is established, maintenance funding can be allocated to ensure that agency priorities are met.
Colorado DOT Example of Funding Needed to Support Maintenance Levels of Service
Source: Colorado DOT. 2016. https://leg.colorado.gov/sites/default/files/cdot_smart_2017_presentation.1.pdf
Washington State DOT
When seeking to establish the connection between investments and performance across a wide range of assets or roadway attributes such as litter, vegetation height, drainage, or functionality it is helpful to relate all of the various measures of performance to a common rating scale. Washington State DOT has developed its Maintenance Accountability Process to establish the relationship between maintenance level of effort and the resulting level of service. The process rates conditions and services in seven areas using a common letter-grade system, or MLOS.
- Roadway Maintenance & Operations.
- Drainage Maintenance & Slope Repair.
- Roadside and Vegetation Management.
- Bridge & Urban Tunnel Maintenance and Operations.
- Snow & Ice Control Operations.
- Traffic Control Maintenance & Operations.
- Rest Area Operations.
Each group of services or conditions includes several performance measures, which are translated to the MLOS grades of “A” (highest performance), “B”, “C” (adequate performance), “D” or “F” (unacceptable performance). Applying the MLOS grades allows for a consistent means of rating performance across services and geographic regions. Letter grades can also be represented in photographs of facilities that meet the criteria for each condition state to support communications with stakeholder groups. The MLOS are outcome-based measures that allow the agency to predict the expected level of service that can be achieved based on anticipated budget and work planning decisions. By tracking maintenance expenditures and MLOS results annually, Washington State DOT is able to adjust its maintenance priorities and budgets to address system needs and stakeholder wants.
New Zealand Local Government Act legally requires councils to consult with their communities on their long-term plans. The consultation plan provides an effective basis for public participation in infrastructure decision-making associated with the long-term plan. It includes a fair representation of overall objectives, and how tax levels, debt, and levels of service might be affected by the intended plan and can be readily understood by interested or affected people. The Auditor General recently reviewed plans produced by communities across the country. Key findings highlighted aspects that help define good practice:
- Consultation documents present their information in a concise, readable and understandable way.
- Clear and unambiguous explanations on why proposed taxation and debt increases and significant changes in plans or intentions were considered “affordable” or “equitable” make consultation documents more effective.
- Some communities used a road-trip analogy throughout the document. The analogy makes technical subjects relatable without over-simplifying the issues.
- Some used a personalized approach that connected with people. For example, one uses two primary school children, Maia and Xander, who are pitched as the “champions of the Long Term Plan 2018-2038.”
By focusing on the inclusion of transportation customers, New Zealand municipalities are better able to address customer needs, inform customers of the actions they are taking, and refine work planning practices to address concerns critical to infrastructure operations and customer expectations.
Developing Life Cycle Strategies
Most transportation infrastructure assets have long service lives, lasting years or decades. Making decisions based on short-term performance without an understanding of the long-term cost effectiveness usually leads to higher future costs. Through life cycle management, agencies can develop strategies for maximizing their ability to meet both short- and long-term goals with available resources.
Adopting life cycle management can often achieve desired performance levels at lower life cycle costs than traditional strategies. Improved performance comes from analyzing the impact of various sequences of treatments on the future performance and costs of an asset class or subclass. By comparing the costs and benefits of long-term sequences of treatments, agencies can develop life-cycle strategies which provide the best practical long-term performance at lowest practical long-term costs. The implementation of life cycle strategies also enables an agency to better address its stewardship responsibilities and improve the alignment between agency investments and priorities.
By establishing sound long-term strategies, agencies can minimize the life cycle costs of preserving assets, while also managing asset performance to a defined target, the extent practicable with available resources. While strategies with a short-term outlook may provide better short-term performance, they can greatly increase the risk of higher future costs.
When developing long-term strategies, it is important to differentiate between the primary asset, with a long service life, and elements or components of that asset, that may be repaired or replaced to allow the primary asset to achieve its design life. In the case of pavements, the pavement structure may require several wearing surface replacements, either through overlay or removal and replacement of the wearing surface, to ensure the pavement structure lasts as long as intended. For assets such as bridges or signal installations structural elements or functional components may be repaired or replaced multiple times within the service life of the primary asset. In almost every case the failure to perform these maintenance and preservation actions, or failure to perform them at the appropriate time will lead to reduced service life of the primary asset.
When determining the appropriate treatment for a long-life asset, it is important to understand the root cause of the condition being prevented or corrected. Inexpensive treatments that address the visible or measured condition without addressing the cause of the distress are not cost effective. Examples of such treatments include:
- Thin overlays of asphalt pavements that are displaying structural cracking.
- Painting corroded structural steel members without proper surface preparation.
- Filling leaking bridge joints without proper materials or preparation.
While such treatments may, in some specific circumstances, be needed to provide minimal function or safety until a more substantial repair can be made, they should not be considered part of an optimal life cycle strategy.
Treatments made to achieve or extend the service life of these assets can also address changes in conditions or assumptions that have occurred since the asset was designed and constructed. Examples of these types of treatments include seismic retrofitting or applying scour protection to bridges, or increasing the hydraulic capacity of corrugated culverts by relining with smooth interiors. Each of these treatments reduces the risk of premature failure to an extreme event, and may at the same time address other structural or functional needs, without replacing the primary asset or changing its functional nature, i.e. increasing traffic-carrying capacity.
Life cycle strategies in construction and design stages
Transportation infrastructure assets are expected to provide agencies with a desired level of performance over their design lives. To ensure the desired performance is achieved, decision-makers should consider factors that impact asset service life and future costs at the time of construction. This is commonly performed as part of the project development process to select a preferred design alternative. Factors to forecast should include design criteria, constraints, standards, and risks.
- Environmental and climatic conditions
- Material properties
- Design standards
- Operational constraints
- Construction practices
- Climate change
- Changing customer expectations
- Regional, state and national travel pattern changes
- Advancing technology
Because these factors contribute to asset performance, deterioration and the continued functionality of the asset, they must be considered when developing life cycle strategies in early and later stages of asset life. Life cycle strategies are based on an understanding of how these factors contribute to the rates of deterioration, how well the asset will accommodate future requirements and which treatments are effective in addressing deterioration or slowing the rate at which the asset deteriorates or underperforms.
Operation, maintenance, and rehabilitation strategies
Treatment strategies consider how the asset, once constructed, will be managed to ensure it attains its design life, while maintaining the desired level of functionality. Special consideration should be given to long-life assets. There are three primary reasons short-term strategies are inefficient for long-life assets:
- As long-life assets age, deterioration accelerates, and there is greater risk of performance failing to meet current needs.
- As deterioration increases, the cost of treatments addressing deterioration tend to increase exponentially.
- Inexpensive treatments that restore condition but do not address the root cause of the deterioration will fail prematurely, leading to higher future costs.
These factors are reflected in Figure 4.5, which illustrates these concepts using a generic asset deterioration model. As shown in the figure, the average cost of treatment increases substantially as assets age. Additionally, the rate of deterioration tends to accelerate as assets age. Long-term strategies that use low-cost treatments early in an asset’s life cycle tend to improve asset condition very cost-effectively by deferring the need for most costly repairs.
Figure 4.5 Example Showing the Cost of Deferred Treatments
Source: Applied Pavement Technology, Inc. 2018
South Dakota DOT
To analyze the benefits of potential actions at the network level, South Dakota DOT (SDDOT) uses incremental benefit cost (IBC) analysis and deterioration models to determine the combination of feasible reconstruction, rehabilitation, and preventative maintenance treatments and timing at the network level that will give the best overall pavement and bridge conditions at the lowest practicable life cycle cost.
IBC analysis is used to answer a series of two important questions regarding pavement section treatments: Should the section be improved now, and if so, what is the best improvement to make? SDDOT’s IBC analysis process answers this set of questions by determining the combination of feasible reconstruction, rehabilitation and preventative maintenance treatments and timings that will use the anticipated state funds to yield the optimal overall asset conditions on the state highway network over a 20-year analysis period and the best long-term value to the system users (SDDOT TAMP, 2018).
Considering Transformational Changes in Life Cycle Management
Life cycle management requires an understanding of past performance to predict future performance and plan appropriate actions. However, as technology advances and society’s needs change, the inputs and objectives of life cycle management need to adapt. Technology can lead to new materials or techniques that allow agencies to get longer life from existing assets. However, technology can also lead to broader societal changes that may make the need for some assets obsolete. Similarly changes in standards and regulations, may make it necessary to replace or update some assets prior to the planned ends of their service lives. Asset managers should regularly review their assumptions about anticipated asset service lives, consider new treatment options, and adjust to technological and regulatory trends and adjust the life cycle approach accordingly. Much of the information to support this effort can be found in agency’s long-term planning documents, as discussed in Chapter 2.
Incorporating Resilience in Life Cycle Strategies
Environmental changes such as extreme weather, temperature rise, sea level change, and changes in other environmental conditions can threaten transportation infrastructure. Even when these changes don’t increase the risk of failure, they can require infrastructure owners to change their strategies for managing assets. This is particularly important for long-life infrastructure assets such as bridges, pavement, culverts, and geotechnical assets.
Resilience is the term used to describe an asset’s ability to withstand environmental changes. Resilience can be considered at all stages of an asset’s life and should be an integral aspect of any life-cycle strategy.
FHWA developed the Adaptation Decision-Making Assessment Process (ADAP) as a tool for planners and designers to address resilience in the design of infrastructure projects. While ADAP was developed to be used on a project-by-project basis, it can also be applied to the development of a lifecycle strategy. Figure 4.6 shows the 11 step ADAP process. The key difference between applying the ADAP process to developing a life-cycle strategy, as compared to a project, is in step 1. Understand the site context. When applied to a project this step is focused on a specific physical location, bounded by the project limits. When applied to developing a life-cycle strategy, the site context will likely be broader to an area that is expected to be subject to a given environmental change, such as increasing seasonal temperatures, or sea level rise. Once the proper context is established, the process steps can be followed to evaluate potential strategic adjustments that will allow life cycle management practices to account for the anticipated effects of the environmental change.
Figure 4.6 Decision Tree of the ADAP Steps
Source: FHWA. 2016. TEACR Engineering Assessment. Adaptation Decision-Making Assessment Process (ADAP). FHWA-HEP-17-004
New York State DOT
In 1994, New York State DOT (NYSDOT) determined that it needed to modernize its bridge designs to have longer service lives to help reduce future rehabilitation and replacement costs. Prior to this effort, the agency designed bridge decks for a 50-year service life with a planned rehabilitation at year 35. The goal for this effort was to double the bridge deck design life to 100 years with a planned rehabilitation at year 75. The NYSDOT Materials Bureau investigated the major causes of bridge deck deterioration and determined that the primary cause of failure was corrosion of the reinforcing steel due the intrusion of chlorides from winter maintenance activities. Upon further investigation, it was determined that the chlorides were penetrating the bridge decks both through cracks and the natural porosity of the concrete. As a result of this research, the agency began a research and development effort to design a new standard concrete mix design that had lower permeability, higher resistance to cracking, and was pumpable to support standard bridge deck construction practices.
The result of the Materials Bureau’s effort became NYSDOT’s “Class HP” concrete, which utilizes fly ash (a byproduct of electric power production) and micro silica (a byproduct of electric arc furnaces used in manufacturing) to replace some of the Portland cement in its standard bridge deck concrete. These new materials are finer in size than cement particles, resulting in well graded denser packing of particles in the concrete, which reduces permeability. Class HP also creates less heat while it cures (or hardens), which reduces the occurrence of thermal shrinkage cracks when the deck cools. In 1997, Class HP became NYSDOT’s standard concrete mix for bridge decks. By using a failure mode analysis to identify the primary causes for bridge deck deterioration, NYSDOT could use new materials technology to address those causes and significantly lengthen the design life of its bridge decks.
Maine is a cold-weather state with soils that are susceptible to severe frost conditions during winter months. In cooperation with FWHA and its Transportation Engineering Approaches to Climate Resiliency (TEACR) effort, Maine DOT undertook a project to assess the impacts of changing climate on the performance of pavements and develop strategies to offset those changes. The study looked at anticipated changes in both temperature and precipitation over the course of the 21st century. The study followed the ADAP process as shown in figure 4.6. The study indicated that anticipated climatic changes will lead to moderate changes in pavement performance. The study identified both engineering and operational adjustments Maine DOT can adopt to address these changes. The full report can be found on FHWA’s website at: https://www.fhwa.dot.gov/environment/sustainability/resilience/ongoing_and_current_research/teacr/me_freeze_thaw/
Life Cycle Management Approaches
Different types of assets require different management approaches to operate effectively and provide the expected level of service. This section introduces common management approaches used by transportation agencies to appropriately manage asset service life at both a network and asset level.
Virtually all transportation infrastructure assets are designed to have long service lives, lasting years or even decades. This means life cycle management must include long-term predictions that come with inherent uncertainty. Further complicating matters, the condition or performance of some assets may be difficult, expensive, or impossible to discern. This is most common with geotechnical assets or hidden elements on complex structures. Addressing this uncertainty requires integration with the agency’s risk management practices, and consultation with technical experts, such as hydraulics and geotechnical engineers. Risk management practices are discussed in more detail in Chapter 5. This section highlights how uncertainty should be considered when selecting a management strategy to maximize service life and address risk.
A condition-based management approach is the life cycle management approach that is the most commonly associated with asset management at U.S. transportation agencies. In condition-based management the condition of an asset is measured, and used to forecast and identify the onset of failure. Maintenance and preservation activities are identified to address the failure and restore or extend service life. While the objective of asset management is to support the reliable performance of the asset, the performance measures most commonly used for physical assets are condition-based. Agencies that are very advanced in their asset management practices may be able to apply the condition-based management approach to other aspects of asset performance.
Condition-based management relies on the collection and analysis of asset condition and defect data. This data is then used to understand the current state of individual assets and when aggregated is used to predict the future condition state of similar asset types. When linked with intervention data and condition threshold information, the future impact of potential actions can be assessed, all with the view of optimizing an asset’s service life cost-effectively. Accordingly, a condition-based management approach combines condition monitoring with performance predictions and knowledge of preventive or restorative actions, to establish a cost-effective life cycle plan. The condition-based management approach can be applied to simple and complex assets, groups of single assets or a whole network. In a network perspective, components could be individual assets such as pavement segments and bridges and at a project level, components could be elements of individual assets.
Overhead sign structures are critical to safe and effective highway performance since they support signs, cameras, sensors and other equipment in support of routine and emergency operations. These structures typically have long service lives, but failure risk exists if they are not maintained. Indiana DOT found that failure to their overhead sign structures could be effectively mitigated through routine, real time condition monitoring and condition forecasting for predicting failure. Therefore, the Indiana DOT uses a condition-based approach for maintaining its overhead sign structures.
Indiana DOT’s condition-based maintenance approach involves the steps listed below to ensure the overhead sign is installed corrected, material specifications are met, and the connection to the ground is secure:
- Professional engineers perform inspections
- An asset inspection report is developed
- The asset inspection reports are submitted to the districts
- The districts review the reports and prioritize work activities
- Work orders are developed to address the highest-priority needs
- In-house crews or local contractors perform the work
As a result of the DOT’s condition-based maintenance approach, the department realized an increase in the amount of collaboration between districts and an improvement in how overhead sign structure repairs and replacements are monitored and prioritized.
Source: FHWA (2019). Handbook for Including Ancillary Asses in Transportation Asset Management Programs (pending publication in 2019).
Interval-Based Management (Age Based)
Interval-based Management is most commonly applied to operations assets (striping, signs, guardrail), where just an inventory is maintained. Condition assessments may not be financially feasible or practical. Additionally, these assets are often related to compliance, meaning their condition state either meets a specific standard, or does not. With interval-based management, asset performance data or manufacturer’s suggested life estimates are used to establish a time interval representative of the service life beyond which the cost of asset failure outweighs the cost of replacement. The service life being the average life that all assets or components of a type are expected to last. Cyclically applied interventions can also be classed as interval-based management strategies, as there is a fixed period between a set of predefined actions that have to be taken. An interval-based approach is most commonly applied to manufactured assets with highly uniform performance levels. It is less applicable to assets constructed on site or long-lived complex assets where there is a greater level of uncertainty surrounding the expected life of the asset. Examples of the types of assets that are often maintained on an interval-based approach are signals, ITS equipment, and other mechanical and electrical related items.
Reactive management unlike condition or interval maintenance does not use forecasting to understand the likely timing of an intervention. Accordingly, reactive management excludes all or most actions to address asset condition or performance, until the asset reaches an unacceptable condition state. The condition state may be influenced by accumulated deterioration or a specific event, like a crash or intense storm. Reactive-management is commonly applied to low-value or less critical assets, redundant assets, or assets for which failure represents an acceptable risk. To create a reactive-based management strategy, minimum acceptable condition thresholds must be defined. Reactive management strategies often require an agency to have a mechanism to deliver required work within a specified time frame, to avoid unacceptable levels of risk. This may include properly staffed and equipped in-house maintenance forces or “stand-by” contracts, so work can be dispatched and delivered quickly. Examples of assets managed using a reactive-based approach include fences, brush, lighting, raised pavement markers, impact attenuators, and rockfall.
Selecting the Right Management Approach
The selection of a management approach considers the mechanisms that lead assets to fail to provide their required or desired service, the consequences of failure, available intervention options and related costs.
Factors for Comparing Life Cycle Management Approaches
Failing to achieve a service level target requires an intervention, or reassessment of the reasonableness of the target. If improvement is required, selecting a management strategy is a function of where performance is insufficient. Safety improvements can reduce crash rates, additional lane capacity can improve travel time reliability, operational enhancements can improve emergency response rates and road availability during inclement weather. Where condition is below target, at a network or corridor level, interventions may be required in multiple areas.
Selecting interventions to achieve condition targets for an asset class or subclass is a data-driven, risk-based process. It evaluates what circumstances lead to asset failure, the subsequent consequences of failure, the options available to avoid failure and their costs. Costs should include the cost to monitor/analyze/ manage an asset in addition to the cost to repair. Based on an understanding of these factors, an agency can determine what strategy will be the most appropriate. The three management strategies introduced in the previous section are incorporated into Table 4.2 along with summaries of the various factors used to compare the approaches.
Table 4.2 - Comparison of Management Strategy Approaches.
Adapted from SAE International 2009
|Decision Making (intervention) Approach||Selects intervention based on a forecasted condition exceedance interval.||Asset is treated based on a time or usage basis whether it needs it or not.||Treatment is performed to fix a problem after it has occurred.|
|Data Needs||Inventory information (Asset / Component)|
Historical condition and expert data – deterioration curves
Current condition and defect data
Historical Intervention and cost data – intervention strategies.
Asset / component type and material data
Intervention thresholds for condition
|Inventory information (Asset / Component)|
Asset / component age
Remaining useful life of asset / component
Timing and type of last action
Interrelationships of different interventions, and how they affect the selection and timing of downstream actions
|Inventory information (Asset / Component)
Current Condition data
Intervention thresholds for condition
Historical cost data
|Life Cycle Planning Expectations||Require the ability to understand the effects of different funding strategies.|
Wish to forecast the future condition state of the network or specific asset classes.
Wish to minimize the life cycle cost.
|Wish to gain an understanding of the typical average cost to manage the network or specific asset classes||General costs estimates based on experience.
Limited need to actively manage the asset.
|Considerations||Cost of collecting and analyzing condition information and developing forecasting models.||Diminished cost effectiveness / efficiency compared to condition modeling.|
Does not support knowledge development of asset behavior (inhibiting the move to more cost-effective regimes).
|Often considered immature but is appropriate for assets if only minor consequences occur from a service disruption.|
|Typical Usage Cases||High risk / criticality assets or risk must be more actively managed.|
Large portfolios or high value assets of similar construction forms
Scenario planning is required
Long-lived assets that can have numerous management approaches applied to them.
More advanced asset management planning is required
Cost uncertainty over time must be assessed (stochastic modeling)
|Moderate or low risk assets.|
Mandated manufactures management regimes or Short-lived assets
Buried assets where condition data is hard to obtain.
Assets where the cost to collect condition data is expensive relative to the maintenance activity that is required
|Low risk or criticality assets.
Assets where the effects of accumulated defects are not critical to their functionality.
Assets that are likely to be subject to unforeseen events or impairment e.g. barriers or light poles.
Reliability Centered Maintenance
Several of the principles described in this section are based on a Reliability Centered Maintenance (RCM) approach, a technique that is sometimes used by an agency to identify the most appropriate management method. Looking at an asset or asset class from an RCM perspective helps to select a management approach based on safety, operational and economic criteria. RCM is commonly applied to complicated assets that may require a range of management approaches for different components of the asset.
The RCM process has its roots in the aviation industry related to the mechanical components of aircrafts, but has been adopted across multiple industries for mechanical, electrical and infrastructure assets. Within the highways industry RCM has been considered for ITS assets. More information on the use of RCM for ITS assets has been published by Austroads (2016): Reliability-centered Maintenance Strategy and Framework for Management of Intelligent Transport System Assets.
RCM considers seven fundamental questions to select the most appropriate management approach for a set or type of assets (SAE International 2009). These questions can be applied to the selection of life cycle management approach. Based on the responses to these questions, an agency can determine what maintenance approach, for which parts of the asset, will maximize the likelihood of an asset performing its desired function for the lowest practicable cost. These questions are as follows:
- What is the item supposed to do and what are its associated performance standards?
- In what way can the asset fail to provide the required functions?
- What are the events that cause each failure?
- What happens when each failure occurs?
- In what way does each failure matter?
- What systematic task can be performed proactively to prevent or diminish to a satisfactory degree the consequences of the failure?
- What must be done if a suitable preventive task cannot be found?
RCM can be presented in a decision tree to aid agencies in selecting the best management approach. Agencies can also customize the questions and decision tree to meet their specific need. Figure 4.7 represents a portion of a decision tree customized to select the appropriate management approach for ancillary highway assets. By applying these questions to an asset class, an agency can prioritize asset classes for monitoring and active management. An agency can also determine which assets present limited risks to system performance and can be managed through less expensive means.
Figure 4.7 Maintenance Approach Decision Tree
Source: FHWA. Expected 2019. Prioritizing Assets for Inclusion in Transportation Asset Management (TAM) Programs.
Managing Assets Using Condition Based Management
The condition-based management is the most complex of the approaches introduced in Section 4.2 and requires a commitment to the collection of reliable inventory and condition information over an extended period and the of condition models to predict future deterioration to evaluate the type and timing of various treatment actions in terms of risk and performance.
Using Computerized Management Systems to Optimize Life Cycle Management
For condition-based analysis, computerized management systems are valuable tools for evaluating life cycle strategies. Computerized systems support the larger life cycle management process by providing relevant, reliable information and analysis results to decision makers at the right time.
Condition-based management is common for pavement and bridge assets. Often pavement and bridge decision making is supported by a computerized system that is used to support optimized life cycle management. The results from this analysis provide insights into optimal life cycle strategies for all network assets or for a specific group of assets. These models can be configured to include the effects, maintenance, preservation, rehabilitation, and reconstruction actions. Depending on the type of condition-based modeling approach, uncertainty can also be included.
Various life cycle scenarios can be generated by modifying one or more variables in the analysis. By running multiple network-level scenarios and comparing the results, pavement and bridge management systems can identify viable life cycle strategies and help an agency select the strategy that best achieves the stated objectives.
More information on the use of pavement and bridge management systems is available in the FHWA document, Using a Life Cycle Planning Process to Support Asset Management: A Handbook on Putting the Federal Guidance into Practice. Life cycle planning is a required component of risk-based TAMPs developed by state DOTs (23 CFR 515), that uses computerized asset management systems to establish long-term life cycle strategies for pavements, bridges and other highway assets. NCHRP Report 866, Return on Investment in Transportation Asset Management Systems and Practices, provides an assessment of how state DOTs have implemented asset management systems, including practice examples. The end of this section includes a how-to guide for using a pavement management system for life cycle planning, a requirement for risk-based TAMPs developed by state DOT’s for pavements and bridges on the National Highway System (23 CFR 515).
These computerized systems are designed to develop network-level scenarios for analyzing the impacts of different program variables over long periods of time. Typical pavement management scenarios will cover 10 to 40 years, while bridge management scenarios may need to cover 100 years or more to ensure inclusion of multiple life cycles within the scenario.
Various life cycle scenarios can be generated by modifying one or more variables in the analysis. By running multiple network-level scenarios and comparing results, pavement and bridge management systems can identify viable life cycle strategies and help an agency select a strategy that best achieves the stated objectives.
As required under MAP-21, Ohio DOT conducted a risk assessment to identify the most significant threats and opportunities to its pavements and bridges. The analysis revealed that anticipated flat revenues, combined with the annual increases in cost to pave roads and replace bridges, would lead to significant reduction in conditions without changes to existing practice. The potential deterioration in pavement and bridge conditions were expected to significantly increase future investment needs due to the increase in substantial repairs that would be required.
Following the risk assessment, a life cycle analysis was conducted. The analysis found that by focusing on the increased use of chip seals and other preventive maintenance treatments on portions of the pavement network, the annual cost of maintaining the network could be reduced. A life cycle analysis for bridges showed similar results. The bridge analysis found that with just 5 percent of the NHS bridges receiving a preservation treatment annually, the DOT could reallocate $50 million each year to other priorities. The investment strategies outlined in the TAMP and the changes made to the DOT’s existing business processes enabled the agency to offset the potential negative impact of the anticipated flattened revenue projections.
The differences in the adopted life cycle strategies are compared to the past strategies in the Figure. Although the total number of treatments applied over the analysis period increases, the annual life cycle cost decreases because of the reduction in the number of rehabilitation strategies needed.
Ohio DOT’s Pavement Preservation Strategy Comparisons
Source: Ohio DOT Transportation Asset Management Plan. 2018. http://www.dot.state.oh.us/AssetManagement/Documents/ODOT_TAMP.pdf
Predicting Asset Performance
A life cycle strategy is enhanced by the availability of models and analysis tools that facilitate the evaluation of different combinations of treatment type and timing across the asset class. For this analysis a model that predicts future asset deterioration and response to treatments is required.
For condition-based approaches to managing assets, historical performance is typically used as a baseline for developing models to predict future performance. The predicted conditions are used to determine the type of treatments that may be needed over an asset’s service life, so the ability to accurately predict asset conditions in the future, with and without treatment, is an essential component of asset management. Models are developed by comparing performance, typically measured as asset condition, over time with actions or treatments performed on specific assets. This means that performance is associated to the last action or treatment that impacted performance in a positive way. However, assets may also receive treatments that delay the onset or advancement of distress. As a result, most models assume assets receive some level of preventive or routine maintenance between more significant treatments. If agency practices change to delay or cease maintenance activities, assets may not perform as models predict.
Several methods can be used to estimate future asset performance, the two most
common of which, deterministic and probabilistic, are described below. Additional information has been published by NCHRP (Report 713, 2012): Estimating Life Expectancies of Highway Assets. This report also contains guidance on selecting the most appropriate modeling approach for various highway asset classes.
Deterministic modeling is a common and relatively simple approach for using historic data to predict future asset performance. Deterministic models apply regression analysis to one or more independent variables, typically condition over time, and develop a “best-fit” equation to determine the rate at which asset conditions change. The independent variables are used to predict a single dependent variable, most commonly represented as the predicted condition at some point in time in asset management applications. Developing deterministic models is relatively easy but relies on quality data collected consistently over several years to produce dependable results. Deterministic models are more easily implemented as they are more readily paired with linear program solving. They also provide consistent outputs. The downside of deterministic models is the limited insight that they provide into the cost uncertainty surrounding a strategy.
Unlike deterministic models, which provide a single repeatable outcome, probabilistic models provide a distribution of possible strategies that provides insight into the cost uncertainty of plans. Probabilistic models can also more readily accept uncertainty in other variables, as represented by the shading in Figure 4.8. Given that condition changes are probabilistic, no two strategies that the model will provide are the same. This means that multiple iterations of the model with the same inputs can provide different results. Accordingly, probabilistic models are useful for setting funding limit expectations, while deterministic models help to provide insights into which projects are best to apply to specific assets.
Common approaches to developing probabilistic models are the Markov, Semi-Markov and Weibull models. Markov modeling works well for assets with condition ratings based on regular inspections. There are several ways of establishing a Markov model, but the simplest is to calculate the proportion of assets that change from one condition state to the next in any given year. These proportions are then used to develop what is known as the transition matrix. At the start of the model run, an asset “knows” its condition state. Once this is known there is then a probability it will change from its current condition state to the next in any given year. While these types of Markov approaches have been widely used, they do not necessarily model deterioration effectively, as the rate of change of condition increases with time. To address this, Semi-Markov models are used. Like Markov, Semi-Markov models have a condition transition matrix, but this is also augmented with a time selection matrix. In these models the probability of a condition jump is calculated, then the length of time an asset will remain in that condition state is also selected. Using more advanced mathematical techniques, the Semi-Markov approach can be expressed similarly to the Markov approach, but for Semi-Markov, the transition matrix changes with time. This reflects the increasing likelihood the asset will transition (deteriorate faster as its ages). Such models are typically used on long-lived assets.
A Weibull model offers another approach for modeling asset deterioration. A Weibull distribution predicts the likelihood of asset failure or deterioration as a function of age. Weibull models are particularly useful for addressing assets rated on a pass/fail basis during inspection. The Weibull model provides an additional factor meant to address the increasing or decreasing likelihood of an asset moving from an acceptable to an unacceptable state between inspection cycles. Reliability is the inverse of the probability of failure (i.e. 1 -p(f)). Reliability, like Weibull can thus be used to assess the likelihood an asset will provide the required service. The relationship between time and reliability is assessed by analyzing asset behavior to understand potential modes of failure. This analysis is a core aspect of reliability-centered maintenance, and is more typically used on short lived assets.
Figure 4.8 Example of a Probabilistic Model
Source: Adapted from Transportation Research Board. 2012. Estimating Life Expectancies of Highway Assets, Volume 1: Guidebook. https://doi.org/10.17226/22782.
Accounting for Uncertainty in Asset Performance
Performance modeling uses historic data to estimate future performance; however, not all future events are predictable nor is past performance necessarily a predictor of future performance. This section considers how uncertainty can be introduced into the analysis.
The unpredictability of future events introduces uncertainty into prediction models. Additionally, the amount of uncertainty tends to increase with time so their affects are compounded. As outlined in the previous section, probabilistic modeling is one approach that can be used for accounting for uncertainty, but what level of uncertainty is acceptable?
To minimize uncertainty, an agency must first understand the source of the uncertainty. A common type of uncertainty related to asset management is the behavior of the assets themselves. Due to the advancement of technology and knowledge and differences in materials and construction practices, there can be significant differences in performance between otherwise similar assets. The change in behavior can be positive, such as the introduction of epoxy-coated reinforced steel in bridge decks to delay the onset of corrosion from road salt intrusion or the introduction of Superpave and performance graded asphalt binders to reduce pavement cracking and rutting. Other changes in behavior are less easy to predict, such as the impact of salt intrusion on prestressed, post-tensioned concrete box-beam bridges. Other sources of uncertainty include:
- Weather events, e.g. flooding, drought, or freeze-thaw
- Climate change
- Traffic accidents
- Data inaccuracies
- Inaccurate models
- Poor assumptions
Uncertainty caused by variability in the data can often be addressed through the development of quality assurance plans that describe the actions an agency has established to ensure data quality, whether the data is collected in-house or by a contractor. Common quality assurance techniques include documented policies and procedures to establish data quality tolerance limits, independent reviews of collected data, and training of data collection crews. Data management strategies are discussed in more detail in Chapter 7.
To evaluate the accuracy of models and assumptions, agencies can include multiple scenarios in their life cycle planning analysis to test the impact of different decisions. This type of sensitivity analysis can be helpful in identifying areas in need of further research or developing contingency plans if the initial assumptions turn out to be inaccurate.
To understand whether time and effort should be invested in minimizing uncertainty, a risk-based approach can be used. Assuming the consequence arising from a defined issue or event remains the same, the cost in terms of data collection of reducing uncertainty can be investigated. As an example, the condition state of an asset, as determined using a visual approach, may not provide the required level of insight, which results in poor or unknowable treatment decisions. To minimize the uncertainty, extra testing can be carried out. The level of testing would be defined by the risk-cost reduction ratio. Similarly, with climate change, how much would have to be invested in studies to understand the effects on asset longevity? Thus, through risk management, an agency determines which risks are tolerable and which must be actively managed through investigations, studies, and other research. The risks are identified, prioritized, and tracked using a risk register (see Chapter 2). For those risks that should be managed, plans are developed to outline actions that will be taken to mitigate threats or take advantage of opportunities, as discussed in Chapter 6.
Halifax Regional Water Commission
Halifax Regional Water Commission (Halifax Water) has employed a deterministic modelling approach to create a plan for their storm water assets. The management system was used for long-term planning their culvert portfolio (approximately 1744 cross culverts on 3700 lane km of regional roads). The software uses deterioration curves, a temporal model periodic simulation model and has integrated Geographic Information System (GIS) capabilities.
Initially the analytical objective of the model was to maximize the average condition of all the culverts and minimize the investment. Several constraints were embedded within the initial model analysis including:
- Non-Increasing percentage of culverts in critical condition
- Replace all culverts that exceed expected useful life
- Budget not to exceed scenario
The scenario analysis allowed Halifax Water to establish a minimum investment level required to bring the portfolio to an acceptable average condition state, have a reliable forecast of future condition trends, and quantify an estimate of accepted risk of failures. The figure below shows the agency’s forecasted risk of failure over time based on the selected strategy and projected funding.
Applying Other Life Cycle Management Approaches
Assets that are managed using an interval-based or reactive management strategy require different approaches for planning and optimizing work than assets managed using condition. The life-cycle plans for these assets range in terms of sophistication depending on the available data.
When to Use Approaches Other than Condition-Based Management
Condition-based management requires a commitment to reliable asset condition information. The necessary level of effort is not likely to be appropriate for some assets. Some assets do not lend themselves to management using a traditional condition-based management approach. The five most common reasons assets do not fit a condition-based approach are as follows:
- The assets do not have a typical life cycle – This group of asset classes includes rock slopes or other perpetual features that do not have predictable deterioration patterns.
- The assessment of condition or performance may not be feasible – The most common type of assets in this second group are geotechnical or utility assets for which many elements may be buried or otherwise inaccessible. The absence of a rating methodology may also drive the management of assets using something other than a condition-based approach.
- The life cycle is driven by factors other than condition – There are many assets that are replaced when they are worn out or obsolete. Technology assets, which are susceptible to obsolescence at a frequency similar to their functional service lives, are examples of assets that fall into this category.
- The assets have long service lives and the failure of individual assets presents limited risks to safety or system performance – Examples of these asset classes include guardrail, gravity retaining walls, or highway lighting.
- The performance expectations require the asset to remain in near-new condition. For safety-critical assets, replacement may be necessary before signs of deterioration are evident. This is most common in risk-averse industries such as aviation. However, contractual arrangements, such as in public-private partnerships (P3), may require condition or performance targets that warrant a life cycle management approach other than condition-based.
As discussed earlier, assets that fall in these categories are typically managed using an interval-based approach or a reactive approach. Some agencies also use a risk-based approach for certain types of assets, such as rockfall management. These three different approaches are briefly explained, and examples are provided for each approach.
Alternative Life Cycle Management Approaches
Three alternative life cycle management approaches are discussed in this section. These are interval- or age-based strategies, reactive strategies, and risk-based strategies.
Interval- or Age-Based Management
Interval- or age-based strategies can be utilized for failure-critical assets, assets subject to obsolescence or assets with no or limited maintenance actions. Age-based strategies replace assets after a given time in service without regard to the asset’s condition at that time. This approach can also be used for very short-lived assets, such as paint markings. Advantages include proactive minimization of failure and reduction of uncertainty in funding needs. An agency that replaces signs on a 7-year cycle or replaces pavement lane markings annually is using an interval- or age-based approach to manage its assets.
Interval-based strategies are also useful for assets that do not show physical wear, but are safety- or operations-critical.
Reactive strategies can be used for assets that have long service lives and limited maintenance options. Reactive strategies can be based on the results of an on-going monitoring program or on event reporting. Examples of assets that may be monitored periodically to check that they are working as intended includes retaining walls and overhead sign structures. Assets that may be more likely to be maintained based on a report that the asset is damaged or no longer working include light bulbs and guardrail.
While all management strategies are risk-based, there are times when risk assessments are used directly as the measure to establish objectives, set targets, drive decision making, or assess progress. This approach is used when the condition of the asset does not directly represent the level of asset performance, and the potential impact of an asset’s condition on system performance must be considered. This approach is commonly used for managing slopes and other geotechnical assets.
Nevada DOT recognized that the level of investment in ITS equipment (e.g., closed-circuit cameras, dynamic message signs, flow detectors, highway advisory radios, environmental sensor stations, and ramp meters) was increasing significantly and the importance of this equipment to network operations was growing. As a result, the DOT chose to establish a method of managing its ITS assets that would minimize the risk of failure and provide information to support budgeting activities. However, since the DOT had limited data on its ITS components, a process was developed that relied on the following factors to establish maintenance cycles:
- Historical performance
- The typical timeframe before the software became outdated
- Manufacturer recommended service life
- To determine the condition of ITS traffic cameras, Nevada DOT developed a transition probability matrix with four condition criteria based on the device manufacturers’ recommended service life as follows:
- Good – device age is less than 80 percent of the manufacturer’s recommended service life
- Low risk – device age is between 80 to 100 percent of the manufacturer’s recommended service life
- Medium risk – device age is between 100 to 125 percent of the manufacturer’s recommended service life
- High risk – device age is greater than 125 percent of the manufacturer’s recommended service life
The transition probability matrix was used to model ITS asset deterioration and program maintenance actions over a 10-year analysis period via the use of a simple spreadsheet tool. The results of this analysis showed an interval-based approach to managing ITS assets would result in an estimated savings of $1.1 million over a 20-year period.
Source: Nevada DOT TAMP (2018)
Colorado DOT responds to between 50 and 70 geotechnical emergencies a year. The traditional approach to managing rockfalls was based on the size and frequency of rockfalls. This approach did not consider the criticality of the facilities that could be impacted by a geohazard event. Since 2013, the Colorado DOT has used a risk-based approach to evaluate and prioritize geohazard mitigation activities based on the size of the geohazard areas and the frequency of falls. Colorado DOT’s approach includes a measure of Risk Exposure (RE), which is based on three components:
- Average Annual Daily Traffic (AADT).
- Likelihood of a Vehicle Being Affected by a Geohazard Event. This metric considers site-distance, the number of previous rock-fall accidents, and a measure of how frequently a vehicle is below the hazard on a daily basis.
- Reduction Factor. This considers the effectiveness of prior mitigation actions, to reduce the RE score.
Colorado DOT’s geohazards program uses the RE to allocate an annual budget of about $10 million to manage geohazards. Due to the inherent uncertainty of geohazard management, in addition to the geohazard management program, maintenance staff regularly patrol highways known to have geohazards. If a hazard requiring immediate action is identified, maintenance crews respond promptly. Using the RE for prioritization allows Colorado DOT to focus its efforts on reducing the impact of geohazards on users of the highway system.
Implementing Life Cycle Management
Implementation of life cycle management often requires agencies to review existing data sets, processes, and policies to ensure that the recommended scenarios are reflected in the projects and treatments that are programmed and constructed. Within transportation agencies, this often requires improved coordination between business units such as planning, programming, engineering, maintenance and operations. Information about strengthening organizational communication and coordination was discussed in Chapter 3.
This section focuses on the aspects of implementation that are most directly related to using life cycle management results to maximize the service lives of infrastructure assets as cost-effectively as possible. It highlights the need to evaluate agency policy, data issues, and work processes to support life cycle management.
Linking Life Cycle Strategies to Asset Management Policy
Agency policies influence the types of decisions that are made within an agency and the priority with which activities are funded. The life cycle management approach selected for each asset class will impact the type of policies, procedures, and data required to support investment decisions to ensure alignment between planned and actual work activities.
Aligning the organization to support the implementation of life cycle management strategies involves many of the same types of organizational change processes discussed in Chapter 2. As part of this alignment, an agency must ensure that it has in place the processes and resources needed to deliver the work activities required for executing the selected life cycle strategies.
Chapter 2 introduced the importance of establishing Asset Management policies to help integrate asset management at all levels of an organization. An Asset Management policy can support life cycle management by establishing processes for setting realistic performance objectives and treatment strategies that focus on a commitment to sound, long-term investments. The following examples demonstrate how agencies can select a life cycle approach that supports the agency’s higher-level policies.
The following hypothetical examples show how policy and management strategy work together to deliver transportation services and manage risks.
Reactive Strategy Example – Agency A has determined its guardrail inventory is generally in good condition and typically replaced as part of pavement rehabilitation projects. On average, replacements occur at least every 30 years, which is more frequent than the expected service life ranging from 40 years for cable to 75 years for concrete barrier. As a result, the agency can accept a life cycle strategy of maintaining a complete inventory and annual inspection of a random two-percent sample.
This life cycle strategy introduces the risk of a rail being damaged by collisions or other events and left in service, presenting a danger to highway users. To manage this risk, the agency implements a policy of repairing all damaged guardrail within 3 weeks of becoming aware of damage. Additionally, internal procedures are put in place to notify area maintenance managers of incidents reported through the state police accident reporting system, and standby maintenance contracts are established for guardrail repair to ensure adequate resources are available in compliance with the new policy.
Condition-Based Maintenance Example – Agency B has determined it can provide significant, long-term performance improvement in average bridge condition and service life if it can increase its investments in bridge maintenance activities like sealing concrete, repairing joints and spot painting steel. To fund this initiative, however, the agency must replace three fewer bridges on average each year. The short-term impact of this new life cycle strategy is an increase in the risk of unsafe conditions occurring on bridges that would have been replaced under the previous strategy. To overcome this risk, the agency increases the frequency of inspections on bridges exceeding the level of acceptable risk according to analysis from its bridge management system, and a series of standby contracts are established to provide rapid response of specific structural repairs to extend the service lives of poor bridges by addressing only critical structural deficiencies or risks.
Data Required for Implementation
All life cycle management approaches need inventory and performance information, but the extent, detail, accuracy, and precision of the required information varies greatly given the chosen approach.
Assets that are managed using a condition-based approach rely on detailed inventory and performance information so that current and future conditions can be estimated, and the benefits and costs associated with each viable strategy can be evaluated. Interval-, time-based, and reactive approaches can be performed with less detailed information about the assets. Agencies using these approaches may estimate the size and age of the inventory at early levels of maturity. Over time, the type of information available and the level of detail associated with it may improve, allowing the agency to mature in terms of its analysis capabilities.
Table 4.3 provides examples of typical management strategies for common highway asset classes and the types of information used to support each one. The information in table 4.3 reflects general trends in transportation agencies. In practice, each agency must identify the specific elements and data requirements needed to support their needs within resource constraints. Chapter 7 addresses methods of collecting information efficiently (see table 7-3) and Chapter 6 stresses the importance of keeping inventory and performance data current. Establishing data governance structures to manage asset data is also an important consideration, as discussed in Chapter 7.
Table 4.3 - Typical Maintenance Strategies and Supporting Data
|Asset Type||Typical Maintenance Strategy||Typical Information Collected and Used|
|Pavements||Predictive, condition-based maintenance||
|Bridges||Predictive, condition-based maintenance||
|Overhead Sign Structures||Monitoring-based or Interval-based maintenance||
|ITS Assets||Interval-based maintenance||
Incorporating Life Cycle Management into Work Planning and Delivery
Life cycle management approaches and corresponding life cycle strategies are the means by which agencies identify the work necessary to meet their asset management goals within funding constraints. However, for those asset management goals to be met, the necessary work must actually be delivered. This requires the recommendations from life cycle analyses to be incorporated into the business processes by which the agency identifies, prioritizes, programs, designs, and delivers work. In most agencies this includes multiple business processes and funding streams. The following subsections describe how life cycle management can be incorporated into common processes within transportation agencies.
Planning and Programming
The planning process seeks to identify the set of investments that will effectively and efficiently achieve an agency’s goals and objectives. As an agency alters its approach to managing assets, this may change assumptions previously influencing the planning process. Significant changes in an agency’s approach to managing its assets can require updates to long-range or strategic plans. Similarly, changes in long-term objectives or plans can prompt a change in life cycle strategy or approach.
Coordination is needed between long range transportation planning, performance-based plans such as the TAMP, and programs of work, such as TIPS and STIPs (see chapter 2). In particular there is a need for alignment between the financial planning procedures and documentation between these different efforts and products. Although programs tend to be relatively short term, often 1 to 4 years in length, agencies must identify investment needs several years in advance to ensure projects can be delivered when required. Complex reconstruction or modernization projects can take 10 years or more to deliver from scoping to construction. Thus, it is important to keep planners informed of changes in selected life cycle strategies. Changing new life cycle strategies may lead to significant differences in the projects selected.
Life cycle management is a framework for identifying the appropriate treatments throughout an asset’s service life to maximize performance. Project engineering includes the processes for packaging work into contracts for delivery. Thus, project engineering is responsible for ensuring the right treatment is delivered at the right time and within the anticipated cost. Additional details on work packaging to support asset management are provided in chapter 5.
Maintaining strong internal controls ties project decisions to their impacts on anticipated asset performance. Project schedule changes may cause inappropriate treatments to be applied to assets, resulting in unnecessarily high costs or poor performance. Scope changes often lead to cost changes, and while cost changes may be addressed for a specific project, the funds added to that project would not be available to address other system needs.
Use of Agency Maintenance Forces
Effective delivery requires adequate labor capacity with appropriate training, proper equipment, and necessary materials. Changes in an agency’s management approach can alter the requirements for any of these aspects of maintenance management. The necessary treatments cannot be delivered if a properly sized and equipped crew cannot be assembled. Maintenance staff cannot administer treatments for which they are not properly trained or correctly supplied. Therefore, it may be important to have maintenance management staff actively engaged in the process of identifying preferred life cycle management approaches.
Fredericton, New Brunswick
The City of Fredericton has, over the last 15 years, implemented several life cycle management strategies that have significantly changed how they deliver municipal services with their infrastructure. Three examples are briefly summarized below:
- Long term life cycle planning: Infrastructure accounting policy changes led to the city establishing long term replacement forecasts for each asset class to estimate the sustainable level of funding required for investment for capital budgeting. This required a complete inventory of their assets, changes in how future replacement costs were estimated, as well as changes to the analysis period used for long term planning. At least one life cycle for all assets had to be captured in the forecast horizon.
- The City implemented a Lean Six Sigma strategy to assess processes and how services were delivered. This methodology helped identify efficiency opportunities, but also identified intervention strategies that previously were not considered in project scoping previously.
- The City evaluated its labor and outsourcing policies as a consequence of the lean approach, and in some circumstances, shifted resources to have dual roles for service delivery, or used external service providers to be responsible for infrastructure, or service delivery.
TAM Work Planning and Delivery
The approach used to deliver work can have a major impact on what investments an organization makes, the resources required to perform work, and work timing. Transportation agencies have many options for performing work, including using internal forces to perform work, and/or using a variety of different contracting approaches.
Typically, U.S. transportation agencies perform some or most of their maintenance work internally, and contract out a large portion – if not all – of their capital projects. The line between the types of work performed as maintenance and capital projects varies by organization and is often blurred. Agencies can often use maintenance forces in a flexible manner to perform a wide variety of activities, including preservation activities on pavements, bridges and other assets. However, in the near term, an organization’s maintenance resources – staff and equipment, in particular – are fixed. Consequently, the asset owner is challenged to optimize use of these resources to meet immediate needs, such as winter maintenance and incident response, while performing additional work to improve asset conditions wherever possible.
The ability to contract out maintenance work, such as through Indefinite Delivery/Indefinite Quantity (IDIQ) contracts, provides an agency with flexibility in meeting near-term needs. Other approaches for contracting out maintenance work include use of portfolio or program management contracts in which certain operations and maintenance responsibilities for some group of assets is delegated to a contractor over a specified period of time. Section 4.3.3 provides additional details on considerations involved in outsourcing asset maintenance.
Regarding contracting approaches for capital projects, in the U.S., most transportation agencies rely on Design-Bid-Build (DBB) model for delivering their capital programs. With this approach, the project owner designs a project (or contracts for a private sector firm to prepare a design) and solicits bids for project construction following completion of the design. This provides the project owner with control over the process, but can be time consuming and can result in cases where bids for project construction exceed the expected cost developed during design. In recent years, many transportation agencies in the U.S. and abroad have explored improved approaches to work planning and delivery to accelerate completion of needed work, leverage alternative financing approaches and transfer program and project risk.
All of these approaches are intended to reduce the time from initial conception of a project to its completion, and in many cases transfer risks associated with project completion from the public sector to the private sector. As these examples help illustrate, major trends in this area include:
- Group work together by geographic location or type of work to develop fewer, larger, and more easily contracted projects
- Use Design-Build (DB), Design-Build-Finance-Operate-Maintain (DBFOM) and other contracting strategies, wherein a single contract is awarded to design and complete a project, as opposed to separate contracts for design and construction
- Encourage development of Alternative Technical Concepts (ATCs), wherein a contractor proposes an alternative approach to meeting a contract requirement in the bidding phase
- Select contractors earlier in program/project development through use of Construction Manager-General Contractor (CM-GC) arrangements, where a contractor is selected as Construction Manager while design is still underway
- Use IDIQ contracts and other flexible contracts to provide a more efficient mechanism for performing smaller projects
- Incorporate performance-based specifications, time-based incentives and other specifications in contracts to improve project outcomes
- Outsource operations and maintenance of an asset using program or portfolio management contracts.
Both in the U.S. and abroad there are many examples of public agencies making extensive use of alternative contracting strategies, such as Public-Private Partnerships (P3s) and performance-based contracts to speed project delivery and transfer risk.
While alternate strategies for work planning and delivery hold great promise, all of the approaches described here have advantages and disadvantages and carry their own risks. Use of alternative approaches can save taxpayers money and provide improvements more quickly than a traditional model. Success stories typically result from improving the efficiency of the process and incentivizing the use of better technology and methods, but there are also many cautionary examples in which these strategies have failed to achieve cost savings, time savings or risk transfers as desired. Asset owners should consult the separate body of research in this area (referenced at the end of this section) when exploring the use of alternative approaches and carefully weigh the expected return, advantages and disadvantages of whatever delivery approaches they consider.
Integrating Asset Information Across the Life Cycle
As assets are designed, created, maintained, restored, and replaced, different systems are typically used to keep records of asset characteristics, conditions and work. Ideally, information created at one stage of the asset life cycle is made available for use at the next stage. Techniques, tools and processes are available to manage data for an asset over its entire life cycle from construction or acquisition to disposal.
Integrating information across the transportation infrastructure life cycle is an area of significant interest in the transportation industry. Several terms have been used to describe the collection of processes, standards and technologies for accomplishing such integration – including Civil Integrated Management (CIM) and Building Information Modeling (BIM) for Infrastructure. In 2019 ISO issued its first BIM standard, ISO Standard 19650. This builds on an earlier standard published by the British Standards Institute (BSI).
Traditionally, information created at one phase of the life cycle is archived and not made available to downstream processes. There are substantial opportunities for cost savings by using a shared, electronic model of the infrastructure, defining information needs at each life cycle phase, and establishing procedures for information handoffs across the life cycle. For example, information about assets included in a construction project can be compiled during design and linked to the model representations of the assets. This information can be confirmed and corrected during construction and made available to asset management systems when the project is completed and turned over to maintenance and operation.
Such integration can reduce duplicative data collection efforts, and speed the time required to make decisions and perform work. Implementing these techniques requires much more than adoption of technology supporting 2D and 3D models. A commitment to common standards and processes is needed. Recognizing that this scale of change takes time, maturity models and levels of implementation have been defined to guide agencies in developing roadmaps for enhancing life cycle information integration over time. See the references at the end of this chapter for further information.
Figure 7.3 Integrated Workflow Model for Sharing Information Across the Life Cycle Components
Transportation Research Board. 2016. Civil Integrated Management (CIM) for Departments of Transportation, Volume 1: Guidebook. https://www.nap.edu/read/23697/chapter/5#16
Crossrail is a major design-build project to construct a new railway line across central London (UK). It includes 42 km of track and 10 new underground stations. Project construction began in 2009. The project is being delivered by Crossrail Limited (CRL), currently a wholly owned subsidiary of Transport for London (TfL). Once the project is complete it will be operated by TfL as the Elizabeth Line. The Crossrail project provides a good example of the application of several BIM elements. Early on, CRL established the following objective:
To set a world-class standard in creating and managing data for constructing, operating and maintaining railways by:
- Exploiting the use of BIM by Crossrail, contractors and suppliers
- Adoption of Crossrail information into future infrastructure management (IM) and operator systems
CRL established a Common Data Environment (CDE) with integrated information about the project and the assets it includes. This environment included CAD models, separate linked databases containing asset details, GIS data, and specialized applications for scheduling, risk management and cost management. Data warehousing techniques were used to combine and display integrated information. Considerable work went into defining asset data requirements and setting up standard, well documented data structures and workflows to provide an orderly flow of information from design through construction, and on to maintenance and operation. It was essential to create a common information architecture given that work on each of Crossrail’s nine stations was conducted by different teams, each consisting of multiple contractors. Each station was comprised of over 15,000 individual assets.
Key elements of the approach included:
- A common asset information database with standard templates for deliverables. This database serves as the “master data source from which playlists of information can be created.”
- An asset breakdown structure (ABS) that relates facilities (e.g. stations) to functional units (e.g. retaining walls) to individual assets (e.g. steel piles).
- Asset naming, identification and labeling standards that distinguish functional duty requirements (e.g. a pump is needed here) from specific equipment in place fulfilling these requirements.
- Asset data dictionary definition documents (AD4s) that lay out the specific attributes to be associated with different types of assets, based on the ABS.
- Sourcing of the asset data from design and as-built information.
- A Project Information Handover Procedure specifying the methods of data and information handover for maintenance and operations once the construction has been completed.
- Use of a common projected coordinate system for CAD and GIS data
- Use of a federated data model in which information was maintained within separate special purpose systems, with a common master data model enabling sharing and interpretation of data from the different sources. The master model included elements such as time periods, budget and schedule versions, organizations, data owners, contractors, milestones and key events.
BIM Lifecycle Information Management
Source: Adapted from Crossrail. 2016. Building A Spatial Data Infrastructure For Crossrail. https://learninglegacy.crossrail.co.uk/documents/building-a-spatial-infrastructure-for-crossrail/
How To Guides
Considerations to Support the Successful Implementation of a Life Cycle Approach to Managing Assets
Work Planning and Delivery