Applying Transportation Asset Management to Traffic Signals: A Primer

Chapter 5. Performance Measures and Targets

Identifying objectives is a key element of effective asset management. TAM objectives should align with the vision and mission of the agency. To achieve these objectives, performance measures should then be identified and tracked.

FHWA TAMP Elements: Asset Management Objectives, Measures and Targets, Risk Management
(23 CFR 515.9(d)(1)-(2), (d)(6))

This theme is extrapolated from three TAMP elements: asset management objectives, performance measures and targets, and risk management analysis. Once an agency has developed its asset management objectives, it can move forward in setting performance measures and targets to achieve those objectives. This emerging theme addresses common performance measures for traffic signals asset management that should then ultimately be linked to the agency’s objectives around these assets. Performance measures can provide excellent insights on assets condition and operational status, helping the agency make better data-driven decisions and better assess, manage and mitigate related risks.

Establishing performance targets allows agencies to track progress towards their goals and guide the allocation of resources to projects and programs with significant impacts on performance. Performance targets should be based on projected available transportation funds and aligned with applicable Federal requirements and State goals and objectives. For traffic signals, and most asset classes in general, agencies have found it critically important to track multiple performance measures, aside from age and/or just condition.

Many international transportation agencies and an increasing number of U.S. agencies have noted the importance of tracking asset availability, or the “calculated percentage of time the asset is in a nonfailed state over a period of time. The asset is categorized to be in a failed state if it is in a degraded state or unavailable, or both” (Luk et al. 2013). This definition was created by Austroads, an association of transportation agencies in Australia and New Zealand that creates guidelines, codes of practice and research reports to promote best practices for road management. Austroads describes asset availability as the result of the combined effect of asset reliability/condition and asset maintainability/serviceability, more specifically:

Asset Reliability/Condition—Continuous performance of an asset to its design/intended function without failure under normal conditions during a period of time. It can be calculated as failure frequency or mean time between failure as well as defined by the age and visual condition.
Asset Maintainability/Serviceability—The time it takes to restore the asset when it fails. It can be calculated as the mean down time (i.e., covering fault identification, response and repair time) or assessed by the type and frequency of maintenance performed on the asset (e.g., preventive versus reactive maintenance, maintenance response time).

Austroads explains that asset availability can be enhanced by either improving reliability (i.e., reducing faults) and/or improving maintainability (i.e., quickly identifying and rectifying faults). These two performance measures are further explained and illustrated below.

With the expansion of centralized systems with communication to each signal, it is more feasible to monitor signals for downtime due to power outages, light failures, and other electronically trackable issues than it was years ago, when most signals were operated in isolation with no communications or tracking ability. Agencies now can assess the risk of signal failure/downtime and target fixes (i.e., if a signal has an inordinate number of power outages, it may be justifiable to install a battery backup system to keep the signal operational).

Also, as more agencies quantify their actions (asset deployment or maintenance for example) through a benefit/cost approach, risk for signal failures can be measured more effectively (more traffic moving fast equals higher risk if signal fails) to prioritize proactive maintenance/risk mitigation.

Asset Reliability/Condition

Asset condition is the foundational measure for the health and physical integrity of an asset and the reliability of the asset. In many cases, agencies measure condition based on age or remaining useful life. This is a valid approach, especially when just getting started in asset management for the respective asset class, in this case traffic signals. Agencies are starting to adopt more robust approaches for traffic signals condition, however, including visual condition scores based on visual inspection, age, and component assessments, rather than purely age or overall asset assessment.

Setting Performance Measures—Utah DOT

As part of a strategic goal of preserving infrastructure, Utah DOT sets performance measures and targets for signal systems, such as the percent of signals that are in good or fair condition, based on an annual inspection of all electronics and the physical infrastructure associated with signal systems. Utah DOT collects and posts its data and performance measures publicly, which contributes to its long-term planning success. Further, the agency has benefited from experienced senior leaders overseeing and championing the planning process. The agency lists key measures and targets for traffic signals in its dashboard and provides a visual representation to help convey outcomes to the public. Table 4 illustrates some of Utah DOT’s traffic signal performance measures.

Table 4. Traffic signals and intelligent transportation system performance measures for Utah Department of Transportation.
Measure	Target
Number of traffic signals	–
Maintenance funding/traffic signal	$3,400/year
Connected signals that are communicating	97.5%
Average time to close signal maintenance work order	5 days or less
Signals with preventative maintenance performed	100%
Traffic signals/signal technician	50 maximum
Traffic signals/signal engineer	100 maximum
Construction projects reporting lane closures	90% key routes reporting
Lane closures activated changed or canceled	85% by June 2018
Planned events managed	90% Level 1 events by June 2018
Road weather information system devices operational	95%

Another framework for agencies is the use of Automated Traffic Signal Performance Measures (ATSPM), which were developed as part of the FHWA’s Every Day Counts (EDC) initiative. EDC is a State-based model that identifies and rapidly deploys proven, yet underutilized innovations to shorten the project delivery process, enhance roadway safety, reduce traffic congestion, and integrate automation. (FHWA 2020)

ATSPM, which were released as part of EDC Round 4 (EDC-4), are a suite of performance measures, data collection tools, and data analysis tools to support the objectives and performance-based approaches to traffic signal operation and management. The use of ATSPM ultimately helps the agency improve the safety, mobility, and efficiency of signalized intersections for all users.

ATSPM consist of a high-resolution data-logging capability added to existing traffic signal infrastructure and data analysis techniques. This provides agency professionals with the information needed to proactively identify and correct deficiencies. They can then manage traffic signal maintenance and operations in support of an agency’s safety, livability, and mobility goals. Agencies have been moving to this system to improve safety and customer service, and deal with scarce funding and staffing by providing continuous performance monitoring capability.

Further, several agencies have noted that ATSPM have been helpful in monitoring traffic signals and addressing issues from a centralized location. One of the primary uses for this approach is to make well-informed timing adjustments. Employees at an agency’s central office get alerts and can focus on updating the signal remotely. ATSPM provide agencies with continuous performance monitoring capabilities based directly on actual performance, without dependence on software modeling or expensive, manually collected data.

These performance measures help link TPM and TAM. They improve the understanding of both performance and needs to assist in overall decisionmaking.

Condition Ratings—Connecticut DOT

Currently, Connecticut DOT estimates traffic signal condition based on lifespan, where traffic signals 26 years and older are expected to be in poor condition, and those below 15 years old are assumed to be in good condition. The agency uses the percentage of traffic signals in a state of good repair (good or fair condition, <25 years old) as its traffic signal performance measure. The current traffic signal performance is 74.5 percent (figure 4).

While Connecticut DOT started its traffic signals condition assessment with an age-based approach, the agency plans to move towards a component-based approach, incorporating both age and condition of the traffic signal components.

A pie chart illustrating the conditions rating of traffic signals used by the Connecticut Department of Transportation.

Figure 4. Graph. Connecticut Department of Transportation condition ratings.
(Source: Connecticut Department of Transportation 2019.)

Asset Maintainability/Serviceability

Asset maintainability (sometimes referred to as asset serviceability) is the measurement of the type and frequency of maintenance performed on the asset. Although this may not translate directly to the asset’s reliability or condition, it can provide a good indication of the potential for assets to deteriorate more quickly than planned.

Common maintenance performance metrics may include but are not limited to percent of preventive maintenance versus reactive maintenance, time between initial service request and resolution, and maintenance funding per signal.

Asset Performance Measures—Seattle DOT

Seattle DOT started implementing asset management in 2007. Seattle DOT adopted a process of continuous improvement and expanded its asset management planning over time. ITS was added as a new asset class to its 2015 Status and Condition Report. Seattle DOT includes beacons, Bluetooth/Wi-Fi readers, camera assemblies, the communication network, counters, dynamic message signs, network hubs, radar speed signs, the transportation operations center, and traffic signal assemblies under this category.

Seattle DOT provides descriptions of good, fair, and poor rating standards for all devices, and it includes physical condition and operational condition categories. Performance measures for traffic signals are included as part of Seattle DOT’s Bridging the Gap (BTG) program. BTG was conceived as a nine-year levy program (mainly from a parking tax) in response to 35 years of deferred maintenance due to shrinking transportation revenues. Seattle DOT gained BTG revenue of more than $40 million per year from 2007 through 2015 (the year the report was published). This revenue also allowed it to further leverage grant funding for infrastructure replacements.

Table 5 shows some of the traffic signal and ITS performance measures used for the BTG program. Additional measures are included in the 2015 Status and Conditions report for each device type.

Table 5. Seattle Department of Transportation asset measures and results.
Policy Goal/Performance Measure	2014 Planned	2014 Results	2015 Planned	Goal Met
% of Transportation Operations Center downtime due to planned maintenance	0.01%	N/A	0.01%	Yes
Traffic Signal Assemblies—% of downtime due to planned maintenance	0.01%	N/A	0.01%	No
Traffic signal assembly maintenance events	779	779	770	Yes

Seattle DOT’s program is an example of good asset management planning for signals and ITS for two key reasons: (1) it includes a mature, regularly monitored and reported set of performance measures for ITS and signals; and (2) it relies on the performance measures to demonstrate progress to a public audience and make the case for funding, or at least make a clear link between investment in various assets and the performance outcomes.

Asset Maintainability Metrics—Highways England

In 2017, Highways England, a Government-owned company responsible for operating, maintaining, and improving England’s highways and major roads, developed a guide to introduce performance requirements for its technology-related assets. To address asset failures, the agency introduced performance categories to group failures. Highways England requires that all major asset failures that interrupt operations are raised in its Fault Management System within the first hour of notification. For maintenance of traffic technology assets, Highways England defined three levels: first line (onsite repair), second line (at a technology depot or local office), and third line (at a repair facility or returned to the manufacturer, essentially needing to be shipped to a different location).

Highways England uses performance metrics (table 6) to track the maintenance cycles of assets and prevent recurrent maintenance needs due to temporary fixes. It also tracks downtime for technology devices (including both traffics signals and ITS) across three performance categories (urgent resolution faults, service affecting faults, and other faults). The agency only permits “clock stopping” when a third party or situation prevents prompt maintenance.

Table 6. Highways England maintainability metrics (selected items).
No.	Metric Description	Performance Category 1	Performance Category 2	Performance Category 3
1	Percentage of faults restored within 56 days.	100%	100%	100%
2	Percentage of faults restored within 168 hours.	100%	100%	–
3	Percentage of faults restored within 48 hours.	100%	100%	–
4	Percentage of faults restored within 24 hours.	100%	80%	–
5	Percentage of faults restored within 12 hours.	100%	60%	–
8	Number of Assessment Periods where no more than 4 faults can occur against any individual asset.	1 Assessment Period	1 Assessment Period	2 Assessment Periods
10	Average availability for all assets in the Performance Category within an Assessment Period.	99.99%	99.9%	97.5%

Reporting Framework for Performance Measures

Conveying performance results is just as important as collecting actual data. Utah DOT populates a shareable and transparent dashboard based on its traffic signal performance metrics and targets. The dashboards are published to Utah DOT’s website (Utah DOT 2019). Table 4 highlighted earlier in this chapter and figure 5 are two snapshots from Utah DOT’s dashboard.

A screenshot of an online tool Utah Department of Transportation uses to monitor its traffic signal performance metrics and targets.

Figure 5. Graph. Statewide system condition of traffic signals for Utah Department of Transportation.
(Source: Utah Department of Transportation, 2019.)

Agencies should also look at using their management systems to create internal dashboards for varying levels of the organizations, from technicians to supervisors and managers (e.g., displaying maintainability metrics for supervisors, such as average time taken to address work orders, percent reactive versus preventive). Further, several agencies noted that using these measures can help make the business case for investment to leadership and stakeholders as well as improve internal processes and decisionmaking.

Key Actions

Key actions agencies can adopt or improve upon when implementing performance measures and target setting for traffic signals are listed below.

Develop and Set Asset Management Performance Measures/Targets

Identifying the right set of performance metrics for traffic signals is a critical, early-stage step. It helps drive the data collecting and ensures the agency is meeting its strategic and asset management objectives.

Key Steps:

Review potential performance categories identified in this section (asset availability, asset reliability, and asset maintainability) and examples from other agencies.
Determine which performance categories and specific metrics are most applicable to the agency, based on current needs, future demand, similar metrics captured for other asset classes, and current strategic and asset management objectives. Implementing performance measures should be a phased approach, starting with basic measures such as age and then visual condition. Such a phased approach is one way to ease into traffic signals performance management.
Define the performance measures and set achievable targets based on operational and maintenance plans and available funding.

Develop Reporting Framework and Processes

The agency should develop a dashboard template and produce a high-level quarterly or annual asset management report with executive-level metrics and reporting on key benefits, outcomes, and impacts along with a summary of key initiatives and status.

Key Steps:

Identify what data needs to be collected to adequately track the performance measures and targets selected (as discussed in chapter 3, Asset Identification, in this primer). This may include but is not limited to the age of the asset, a visual condition score (such as 1 to 5) captured regularly, or the amount of time it takes to address a failed asset.
Start tracking data over time using the management system or tool. Once initial/sufficient data have been captured, identify which metrics are meaningful to various individuals (executive leadership, senior management, and supervisors) and how those data be best communicated to those types of individuals (e.g., a supervisor might like to see a dashboard in their management system with maintainability metrics, where a visual dashboard illustrating asset availability across the network may be more appropriate for executive leadership).
Seek feedback from those reviewing reports (or dashboards) to determine if this is the right information and level of detail for those individuals; adjust accordingly.

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