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Applying Transportation Asset Management to Traffic Signals: A Primer

Chapter 3. Asset Identification

A well-developed asset inventory (i.e., what do we have?) provides a basis for setting performance targets, allocating resources, and monitoring progress towards achieving objectives. Although an improved asset inventory for traffic signal assets is a desirable outcome to inform decisionmaking, collecting, maintaining, and managing an asset inventory can be expensive. Before undertaking inventory process enhancements and/or investing additional funds in data capture, agencies should understand what information is important for both current and future asset management decisions.

FHWA TAMP Element: Summary Listing of Assets (23 CFR 515.9(b)-(c) and (d)(3))

Asset identification aligns directly with one of the critical eight elements of a TAMP, a listing or an inventory of the agency’s key assets. Although traffic signals are not currently required in a TAMP, many Agencies desire to have an inventory of all assets within the right-of-way corridor. Traffic signals are increasingly being identified as critical assets to the successful operation and safety of the agency’s infrastructure. Knowing and understanding the status and condition of these assets will allow the agency to make informed decisions about lifecycle planning and investment prioritization. Further, agencies should pay close attention to the type of data they are collecting and tracking against their assets. Tracking too little information will not provide the necessary value to make informed decisions, while tracking too much information results in unnecessary costs and unused data.

When making decisions about asset identification, it is important to consider the following ideas:

  • Asset Definition—What to define/consider as assets?
  • Asset Attributes and Hierarchy—What information should be collected for these assets?
  • Inventory Management—How will the agency collect and manage asset information so that it remains accurate and reliable?

With all these ideas, it is important to consider how the data supports the agency’s decisionmaking relative to its overarching asset management goals, objectives, and performance targets.

Asset Definition

As defined in 23 CFR 515.5, “asset” means:

[A]ll physical highway infrastructure located within the right-of-way corridor of a highway. The term asset includes all components necessary for the operation of a highway including pavements, highway bridges, tunnels, signs, ancillary structures, and other physical components of a highway.

This definition focuses on physical assets and all components necessary for the operation of a highway. However, with regard to traffic signals, asset-management-related factors beyond the physical features and functionality of the traffic signal should be considered. For example, if all the components of a set of traffic signals at an intersection are in good physical condition, they may not function as designed because of old controller software, poor physical condition of a supporting asset, or outdated signal timing plans. These items are critical for maintaining safety and mobility and their condition should be monitored carefully. Agencies should carefully consider including these factors when adopting traffic signals asset management.

Most agencies categorize traffic signals separately from Intelligent Transportation Systems (ITS) assets for several factors such as asset ownership, varying maintenance and operational responsibilities, liability concerns specific to traffic signals, and for the capabilities of recording and managing asset information. While not as common, some agencies include traffic signals and ITS assets in one asset class, especially smaller agencies with fewer assets. Currently, agencies collect a variety of information, from geographic coordinates, conditions, serial numbers, and age to energy consumption, condition of structural support, and driving/work time associated with asset work orders.

Asset Attributes and Hierarchy

Agencies should identify a clear set of baseline data necessary for traffic signals asset management planning. Numerous agencies are just beginning to build out databases and lack a precise understanding of what information will aid future decisions. Agencies should follow an iterative approach when it comes to identifying the type of data to collect for traffic signals.

National Cooperative Highway Research Program (NCHRP) 08-36, Task 114: Transportation Asset Management for Ancillary Assets identifies ancillary asset inventory needs at an enterprise level and asset-specific level (Rose et al. 2014). At an enterprise level, knowledge of the complete asset inventory is recommended along with an understanding of interactions with other asset classes and the relationship of the asset class to overall safety, mobility, and asset performance. At the asset level, inspection and condition assessments, performance metrics, lifecycle management plans and practices, asset priorities, and decision support are all valuable. Further, an asset class and/or an asset subgroup level view of assets can provide powerful insights for addressing, maintaining, and managing a collection of assets. Figure 2 illustrates this framework.

A diagram illustrating the four levels of asset inventory definitions framework.

Figure 2. Diagram. Asset inventory definitions framework.
(Source: FHWA.)

The first decision is the level of detail to be used. Relevant definitions from 23 CFR 515.5, are:

Asset class means assets with the same characteristics and function (e.g., bridges, culverts, tunnels, pavements, or guardrail) that are a subset of a group or collection of assets that serve a common function (e.g., roadway system, safety, intelligent transportation (IT), signs or lighting)....

Asset sub-group means a specialized group of assets within an asset class with the same characteristics and function (e.g., concrete pavements or asphalt pavements).

State and local agencies using these definitions have flexibility to categorize their traffic signals. Although agencies may group their assets along traditional functions (e.g., traffic signals, ITS devices), they can also group assets with other assets that serve a broader function (e.g., intersections). Many agencies start by tracking the traffic signal as a whole, while other agencies have begun tracking the individual asset components that make up the traffic signals. See figure 3.

Two side by side illustrations of a traffic signal. The first has the entire traffic signal labeled as one asset: Signal Asset.

Figure 3. Rendering. Traffic signal assets level of detail.
(Source: FHWA.)

Two side by side illustrations of a traffic signal. The first has the entire traffic signal labeled as one asset: Signal Asset. The second is the same image with individual labels for each component: target board, lantern, pole (mast arm), pedestrian lantern, pedestrian call box, detector cards, controller, detector loop and cabling.

Level of detail is linked to decisionmaking needs. Long-term needs can be calculated based on the expected life of a set of signals. However, components of a traffic signal have differing useful lives (e.g., the mast pole might have a useful life of 40 years, but the signal itself may become obsolete or fail after 20 years). If agencies require component-level information, they can also stage the development of this detail. The focus may start on assets that require periodic maintenance and replacement, which can be planned. If the component replacement is reactive and not planned, requiring a decision about when to intervene, then further asset information is likely to be less critical.

Asset Hierarchy Framework—Oregon Department of Transportation

Oregon DOT’s inventory highlights the importance of location in its asset inventory for both traffic signals and ITS assets—capturing the location, asset class, and asset subgroups. At the highest level of its asset hierarchy, Oregon DOT has traffic signals and ITS cabinets, and then breaks those assets down to lower level assets and components.

Oregon DOT reviews its data regularly and is cognizant of what it is tracking and how the data are being used. The agency is reviewing what lower level traffic signal components should and should not be tracked, as the agency does not want its technicians to get bogged down tracking information that is not necessary. Further, Oregon DOT does track serial numbers for critical components, primarily for warranty management.

Table 2 complements figure 3, outlining some of the common components and attributes agencies can track for traffic signals. Although it is not a comprehensive list, it provides an initial snapshot of what agencies are starting to track for traffic signals. Note that several of the items listed in table 2 (such as signal head and controller), although considered “components” to the traffic signal, can still be tracked as individual assets. This table only shows the potential breakdown of an agency’s traffic signal assets.

Table 2. Common traffic signal components, items, and attributes.
Name Attribute
Traffic Signal
  • Signal Type.
  • Manufacturer.
  • Model/Serial Number.
  • Installation Location.
Signal Head
  • Head Type/Material.
  • Configuration.
  • Lens Type.
  • Bulb Type.
Controller
  • Type.
  • Make.
  • Model.
Communication Devices
  • Remote Communication.
  • Device Type (e.g., GPS clock, radio).
  • System Type (isolated, closed loop, central).
Pole/Structure/ Foundation
  • Pole/Structure Type.
  • Pole/Structure Style.
  • Pole/Structure Base Type.
  • Pole/Structure Length/Height.
Detection System
  • Detection Loop Size.
  • Detection Loop Type.
  • Camera Type.
  • Radar Type.
Controller Software1a
  • Name.
  • Version.
  • Firmware.
Signal Timing Plan1b
  • Last Updated.
  • Key Parameters.
Power
  • Power Type.
  • Uninterruptable Power Supply.
  • Batteries.

1a These can be thought of as specific items or be linked as attributes to one of the asset components (e.g., controller software as an attribute for the controller). [Return to table note 1a]

1b These can be thought of as specific items or be linked as attributes to one of the asset components (e.g., controller software as an attribute for the controller). [Return to table note 1b]

The items referring to controlling software and signal timing plans in this table highlight the importance of considering the functionality of traffic signals in addition to the physical condition as part of the agency’s asset management initiatives. While the physical condition of a signal is critical, the impact to system performance should also be considered. Operating signal assets may involve activities beyond their physical features and cover functionality, such as maintaining controller software and signal timing plans. Consideration of an asset’s functionality as part of an asset management strategy is consistent with the framework for asset management as the term is defined in 23 U.S.C. 101(a)(2).

Asset Inventory Management

Asset inventories should include a procedure for collecting, processing, and updating inventory and condition data. Having a comprehensive, up-to-date asset inventory supports decisionmaking, performance target tracking, lifecycle modeling, projecting funding needs, and allocating funds; however, maintaining a comprehensive inventory of traffic signals can be a challenge. Because traffic signal assets often have short design lives, agencies frequently plan to operate them until they become obsolete or are no longer functioning as originally intended rather than carefully managed over their entire lifecycle, although this trend is beginning to change as many agencies have identified the importance of this asset.

Asset Attribute Collection—Utah DOT

The Utah DOT TAMP outlines a data-driven, performance-based approach to allocating transportation funds to manage its pavements, bridges, advanced traffic management systems (or as referred to in this guide, ITS), and signal devices. The Utah DOT Asset Advisory Committee/Performance Management Group developed a tiered system to prioritize the most valuable assets and those with the highest risk to system operation. To achieve its safety and mobility strategic goals, Utah DOT included traffic signals and ITS devices in the highest tier for management (alongside pavements and bridges). Its highest tier is “performance-based management,” which requires accurate data collection, performance target setting and tracking, predictive modeling and risk analysis, and dedicated funding.

When traffic signals and ITS assets were added as a Tier 1 asset in 2016, Utah DOT needed to ensure that the right data were collected at the right time. Utah DOT understood the importance of having a good management system and, more notably, the importance of having buy-in across the agency and a solid implementation plan for data collection. Utah DOT identified four critical factors for implementing a data collection framework:

  1. Limit the number of assets and attributes being tracked (i.e., focus on the actual assets and data to collect—not collecting data for the sake of collecting data):
  2. Use a robust work order management system (either as part of a comprehensive management system or a system that interfaces directly).
  3. Ensure staff understand the purpose behind the data collection.
  4. Make the hardware for data collection mobile.

These four steps are applicable throughout the Utah DOT data collecting lifecycle of the asset (inventory data, work management data, condition data). Utah DOT noted the importance of taking baby steps. For traffic signals, to ease into implementation, the agency first identified four key attributes it wanted to collect: signal type, key components of that signal, manufacturer, and model. Utah DOT worked with its technicians to convey the need for the information and provide training. The technicians then went to the field and started tracking this information and populating work orders. After about three months, Utah DOT met with the technicians to see how the process was going and identify any problems. Utah DOT then incorporated this feedback, updated the system and/or process as needed, and provided additional training. Utah DOT has continued to expand upon this approach for traffic signals and ITS assets since 2016. The feedback from the technicians helps the agency pinpoint what data and information it wants to collect on its assets.

(Source: Utah Department of Transportation 2019.)

Key Actions

Agencies can adopt or improve upon several key actions when implementing asset identification for traffic signals.

Define and Collect Asset Attributes for Traffic Signals

Agencies should clearly define what information they are tracking against their assets and why they are tracking that information. Many factors may affect attribute collection, including institutional practice, location, safety, and operational criticality.

Key Steps:
  • Similar to what is being tracked for other assets within the agency, an agency should begin collecting basic attributes like name, manufacturer, and install date as well as attributes that are specific to traffic signals. Having a clear list of these attributes will make it easier to explain to employees why certain information is being collected and to aid employees in asset collection and adoption. Further, this list can easily be shared with contractors when onboarding new assets.
  • Add attribute data collection incrementally by introducing new types of attributes over time and/or through a phased approach. Agencies should closely monitor how the data are being collected, when they are being collected, and then obtain feedback from employees while both collecting and using the data. The agency then can adjust its processes around these attributes and begin to introduce additional attributes, as applicable.

Define and Collect Asset Attributes for Traffic Signal Components

Agencies should also define the level of detail they are collecting. This can be done by developing an asset hierarchy, a framework illustrating the relationship between assets and components.

Key Steps:
  • Identify the most critical components of the traffic signal. What components are failing the most or what components are regularly being worked on? Start by identifying these components, and this will become the second layer of the hierarchy for the traffic signal. Table 2 provides a list of common components.
  • Begin collecting a modified list of attributes for these second-level components. As the data are being collected, identify additional components or subcomponents. This will serve as the foundation for the agency’s traffic signal hierarchy.