By Karen Scurry, FHWA, Scott Himes, VHB, Frank Gross, VHB, Kara Peach, VHB, and Catherine Chestnutt, VHB
Countermeasure Service Life Guide. (Source: FHWA)
Transportation agencies often balance many factors when identifying and selecting appropriate countermeasures for improving roadway safety. One component of the decision-making process is a consistent and reliable method for comparing potential benefits of countermeasures for installation. When agencies are selecting and prioritizing countermeasures and projects, they need to reasonably compare the different options and often use crash modification factors (CMFs) to support the analysis. While CMFs help estimate the magnitude of a potential safety benefit, they do not reflect the service life for each countermeasure.
Service life is the number of years a countermeasure will have a noticeable effect on crashes at a location.5 Practitioners incorporate countermeasure service life in benefit-cost analysis (BCA) to support a more comprehensive and fairer comparison of alternatives in the analysis. While FHWA previously produced a synthesis of countermeasure service life values used by States, many States indicated a preference for a single source that contains typical service life for various safety countermeasures.
Overview of the Guide
The Highway Safety Manual Implementation Transportation Pooled Fund study TPF-5(255) sponsored development of the Countermeasure Service Life Guide (FHWA-21-026) for traffic and safety engineers, designers, planners, and maintenance staff who may not have experience with economic analysis. The guide intends to help these practitioners learn more about service lives and how practitioners can include service life as part of a BCA. Ultimately the guide aims to support consistent decision-making when practitioners implement safety strategies or countermeasures for safety projects and programs.
| Countermeasure Category | Service Life (years) |
|---|---|
| Access Management | 20 |
| Advanced Technology and Intelligent Transportation Systems (ITS) |
10 |
| Alignment | 20 |
| Bicycle | 1–25 |
| Delineation | 1–5 |
| Highway Lighting | 15 |
| Interchange Design | 20 |
| Intersection Geometry | 1–20 |
| Intersection Traffic Control | 1–15 |
| Pedestrian | 1–30 |
| Railroad Grade Crossings | 1–25 |
| Resurfacing | 5–10 |
| Roadside | 10–25 |
| Roadway | 1–20 |
| Shoulder Treatment | 5–20 |
| Signs | 5–20 |
| Structures | 10–30 |
| Work Zone | 1 |
| Other | 10–30 |
Jason Hershock, manager of the Safety Engineering and Risk Management unit at the Pennsylvania Department of Transportation, is looking forward to using the guide. He shared, “The new FHWA Countermeasure Service Life Guide will be a tremendous reference for the department. The reference will provide acceptable life cycles for several safety countermeasures, which will provide accurate life cycle cost analysis. Overall, the new Countermeasure Service Life Guide will help the department answer the questions, ‘Is the project worth the investment?’ and ‘Which project options are the best to improve safety given the current budget?'”
The Countermeasure Service Life Guide provides typical service life values for common safety strategies and countermeasures. The development of the guide included a review of existing resources (e.g., State-agency HSIP manual documentation and State-developed countermeasure service life lists) and literature that contained information on the service life of various countermeasures. A technical panel composed of representatives from eight State DOTs met and provided suggestions based on their experiences. The guide organizes the common countermeasures into 19 categories (shown in the table below), which is consistent with those found in the CMF Clearinghouse. The guide provides a single service life value for each countermeasure, and the list includes the range for the typical service life associated with each category.
Potential Applications and Benefits
Countermeasure service life is a key component of the BCA process. Specifically, practitioners can use service life values to select an appropriate analysis period and to use the equations to convert annual maintenance and operations costs to present dollar values. So, it is important that transportation practitioners use a consistent approach and service life values when comparing and prioritizing potential projects. The guide walks through several safety project examples for selecting and applying the service life in a BCA. The examples include practical applications of service life in the BCA process for:
- Commercial motor vehicle-involved fatal work zone crashes
- A new single countermeasure with an unknown service life
- A countermeasure deployment using a systemic approach within a project
Practitioners can use the guide to develop a service life list, which is similar to a CMF list. A service life list offers several benefits, such as creating standardized values that improve how an agency consistently applies BCA on proposed projects. Practitioners like Kevin Scopoline, traffic operations and analysis engineer with WisDOT, shared, “Wisconsin DOT plans on incorporating this guide into our safety analysis process to help compare alternatives as part of the benefit-cost analysis.”
A State-specific service life list will help staff communicate more clearly to decision makers the reasons for selecting a particular countermeasure as well as promote consistent BCA throughout an agency. While the guide provides typical service life values for common countermeasures, it also describes factors that can impact service life.
Availability
The Countermeasure Service Life Guide is available online.
For more information contact Karen Scurry at Karen.Scurry@dot.gov or 202.897.7168.
