Bridge and Tunnel Strikes: A Guide for Prevention and Mitigation (2025)
Chapter: 4 Countermeasure Selection Process
CHAPTER 4
Countermeasure Selection Process
There are often multiple options for addressing crash contributing factors, ranging from higher-cost structure improvements to a specific location to lower-cost signing improvements at multiple locations or more wide-reaching policy strategies. The cost of structural repairs, structure closures, and related injuries may exceed the high installation costs associated with some countermeasures. The countermeasure options typically differ in the level of effectiveness, where higher-cost countermeasures may be more effective at mitigating high-risk locations, while lower-cost countermeasures may be more effective at mitigating risk across the system. As such, agencies should perform a benefit-cost analysis as part of the countermeasure comparison and selection process to quantify and compare the existing systemwide risk and change in systemwide risk under different alternatives. For instance, what is the benefit of a $1 million investment to a single bridge versus a $1 million investment across the system? Given a list of potential countermeasures that target the underlying risk or crash contributing factors, the next step is to perform a more detailed analysis of alternatives to identify the preferred alternative (e.g., most effective, most efficient). This chapter describes quantitative and qualitative measures for selecting and prioritizing countermeasures, focusing on alternatives analysis.
4.1 Quantitative Methods
Benefit-cost analysis and the Safe System Approach are two quantitative methods for prioritizing countermeasures. Benefit-cost analysis can help identify the most economically efficient alternative (i.e., greatest return per dollar spent) by comparing the present-value benefits and costs. The Safe System Approach can help identify the most safety-effective alternative (i.e., greatest potential to prevent death and serious injury) by comparing the countermeasure characteristics to the Safe System principles. The following is an overview of the benefit-cost analysis and Safe System Approach, including references to readily available resources for more information.
Benefit-Cost Analysis
Benefit-cost analysis utilizes monetized project benefits and costs where analysts assign dollar values to the various benefits (or disbenefits) for comparison against the monetary project costs. For example, if there is an expected change in crash frequency associated with a project alternative, compared to the base condition, then the analyst would multiply the expected change in crashes by the average crash cost. Safety-focused benefit-cost analysis includes the expected change in crash frequency, preferably by crash severity. The following is a list of other potential benefit (or disbenefit) categories that could result in changes due to the need for construction or detours around bridges that are under repair after a BrTS.
- Changes in cost for infrastructure repair and maintenance.
- Changes in cost for vehicle and cargo damage.
- Changes in travel time and delay.
- Changes in travel time reliability.
- Changes in vehicle operating cost.
- Changes in emergency service disruption.
- Changes in air emissions.
- Changes in noise.
Project costs typically include the following:
- Design and engineering.
- Land acquisition.
- Construction.
- Reconstruction/rehabilitation.
- Preservation.
- Routine maintenance.
- Mitigation (e.g., noise barriers).
- Utility relocation.
- Energy (e.g., for active warning signs).
For further information on benefit-cost analysis, refer to FHWA’s Highway Safety Benefit-Cost Analysis Guide (Lawrence et al. 2018)
Safe System Approach
As described in Chapter 3, agencies may consider Safe System principles in selecting and prioritizing countermeasures. Countermeasures that align with more of the following Safe System principles are generally preferred:
- Death/serious injury is unacceptable: Agencies should not prioritize mobility over safety. Countermeasures that minimize the potential for crashes and minimize the severity of crashes should be a priority.
- Humans make mistakes: It is understood, and even expected, that humans using the transportation system will make mistakes and that those mistakes will lead to crashes. The intent is not to design a system that is completely void of all crashes. Instead, the intent is to design and operate the transportation system to accommodate human mistakes.
- Humans are vulnerable: A Safe System is one that minimizes forces in collisions to a level that does not exceed the limits of human tolerance.
- Responsibility is shared: It is unacceptable to solely blame road users for their lack of safety on a system that they have little to no involvement in planning, designing, and operating. Roadway owners and operators, vehicle and technology manufacturers, state policymakers, and law enforcement officers share responsibility with the road users in creating a Safe System.
- Safety is proactive: Agencies have an opportunity to address fatal and serious injury crashes before they occur. A Safe System proactively identifies and mitigates risk factors to reduce the chance of death and serious injury. This should be parallel to reactively addressing historical safety issues.
- Redundancy is crucial: Agencies can improve the safety of a system by building in redundancy. If one component fails, another component can prevent or mitigate the severity of a crash. A true Safe System provides enough redundancy to accommodate underlying risk factors without resulting in death or serious injury.
For further information on the Safe System Approach, refer to FHWA’s Integrating the Safe System Approach with the Highway Safety Improvement Program: An Informational Report (Finkel et al. 2020).
4.2 Qualitative Methods
- In addition to quantitative factors, there are several qualitative factors for selecting and prioritizing countermeasures. Chapter 3 described basic qualitative factors for selecting initial countermeasures. Agencies can use those along with the following factors and the quantitative measures from the previous section to prioritize countermeasures for a select location (or projects within a larger program).
- Other planned projects and schedules: Countermeasures that can be implemented sooner and easier may be a higher priority, especially if those countermeasures can be implemented as part of a project that is already planned and programmed. Countermeasures implemented as part of other planned projects reduce construction-related costs and impacts (e.g., traffic delays) and generally provide cost savings for the overall program. The planning and scoping phase is the best time to identify and add safety components to a project, not the design phase (Atlanta Regional Commission 2022).
- Environmental and right-of-way impacts: Countermeasures with positive environmental benefits may receive higher priority than similar countermeasures with no or negative environmental impacts. Those needing right-of-way acquisition may receive lower priority because this presents a potential risk to project schedule and budget (Atlanta Regional Commission 2022).
- Agency familiarity or comfort with countermeasure: Agencies may consider factors such as “familiarity” as part of the countermeasure selection process, prioritizing those that have been implemented successfully in the past. It is also appropriate to consider countermeasures that may be different from typical agency policies or practices, assuming there is sufficient evidence to justify the cost-effectiveness and overall benefits with respect to the targeted risk factors. In these cases, it is useful to identify peer agencies that have demonstrated successful implementation of the countermeasure and include that as part of the project justification (Atlanta Regional Commission 2022).
- Long-term maintenance: While maintenance costs should be built into the quantitative benefit-cost analysis, agencies may prioritize countermeasures with longer-lasting effects and lower long-term maintenance needs. For instance, while it may take months or years to establish new policies or operational procedures, these types of strategies can have long-lasting effects with little to no long-term maintenance.
For further information on countermeasure selection, refer to FHWA’s guide, Selecting Projects and Strategies to Maximize Highway Safety Improvement Program Performance (Gross et al. 2021).
