CHAPTER 9

Countermeasures Identification and Process for Selection

Introduction

This chapter provides an overview of the process to research, identify, and describe potential safety focused countermeasures. Protecting critical infrastructure like bridges and tunnels from potential OSOW strikes requires a multi-layered approach that includes a variety of practices, processes, technologies, and human factors. Selecting the most effective countermeasures isn’t a one-size-fits-all solution – for this project our team considered many sources for input, including prior research and stakeholder engagement. The research team also consulted with the NCHRP project panel to further refine the proposed countermeasures.

In practice, infrastructure owners and operators need to consider the specific vulnerabilities of each structure, potential threats, and available resources. The resulting guide generated through this project includes information on how to select and use certain countermeasures, which can range from physical barriers and enhanced security protocols to advanced detection systems and rapid response plans. By carefully considering these factors, agencies can create a comprehensive defense strategy to safeguard these vital transportation links.

Literature Assessment

Our team completed a Literature Assessment to identify and describe a set of counter measures to include in the guide. In general, the literature and practice describe the need for a multi-layered approach to preventing BrTS. This involves fortifying structures, implementing stricter access protocols, and utilizing detection systems like sensors and video surveillance. Regular vulnerability assessments and threat modeling are crucial to prioritize countermeasures that offer the best balance between effectiveness and cost.

The research team provided a salient summary of literature review on topic areas including BrTS collision characteristics, crash outcomes, and models; the state of practice related to over-dimensional permitting considerations as well as reporting, clearances and transportation asset management. This summary included particular attention to strikes of bridge/tunnel and other highway structures and existing countermeasures (e.g., prevention/mitigation strategies from roadside to in-vehicle technologies). The project team performed keyword searches of research databases such as the TRID and Google Scholar to identify relevant peer-reviewed journal articles, research reports, guidance, and other resources for review.

The literature also indicated that in countermeasure selection, the following considerations need to be included:

1. Safe System principles: Countermeasures adhering to Safe System principles are designed to reduce both the crash frequency and severity, and build in redundancy (e.g., serve as a backup if another system component fails).
2. Community context: Agencies should consider the surrounding land use, function of the roadway, and community context when selecting countermeasures. Engaging local residents and stakeholders aligns

countermeasure strategies with community preferences, using feedback to shape decisions. These choices should be validated with data-driven analysis to effectively meet community needs.

3. Multiple potential alternatives: It is desirable to identify and develop multiple potential countermeasures for comparison. This helps to identify the most effective and efficient option. It may be useful to develop a flow chart or decision matrix to assist practitioners in selecting appropriate countermeasures or mitigation strategies.
4. Cost-effectiveness: Ideally, chosen countermeasures by agencies should effectively reduce the targeted crash types. It is important to also consider the construction and maintenance expenses, as more effective solutions, such as increasing clearance dimensions, typically come with greater costs.
5. Service Life: As per the Highway Safety Manual (HSM), service life of a countermeasure is defined as “the number of years in which the countermeasure is expected to have a noticeable and quantifiable effect on the crash occurrence at the site” (American Association of State Highway and Transportation Officials (AASHTO) 2010). This concept is crucial in cost-benefit analyses, helping to translate annual costs and benefits into present values, and is especially pertinent when the analysis period does not align with the service life or when comparing different alternatives with varying lifespans.

The research team used these principles to identify the list of countermeasures presented in the Guide.

Stakeholder and Community Partner Engagement

Following the submission of the literature review, the project team also completed a set of industry and agency surveys and interviews. These opportunities to engage practitioners directly leveraged the team’s knowledge and provided insights into the challenges and other insights on how to develop effective bridge strike prevention strategies.

First, through the surveys and interviews with representatives from the trucking industry and relevant government agencies, the team identified varying perspectives on bridge strikes. Industry insights revealed common challenges drivers face, including confusing signage, overreliance on digital maps, or unclear permitting procedures. Agency perspectives offered common issues for existing detection and enforcement methods, as well as resource limitations.

Beyond surveys and interviews, our team was also able to develop targeted driver outreach materials including countermeasures and provide that with a Guide. We learned about programs for professional drivers and the general public currently offered by trade organizations. Through this collaborative approach, the research team prepared a list of countermeasures that were useful to the community. We were able to gather valuable data but also build potential support for bridge strike prevention strategies, ensuring their long-term effectiveness.

Panel Review and Comment

Upon submission of the content and list of countermeasures to the panel, we are able to further hone and refine the countermeasure presentation and utility. For example, panel comments highlighted some new in – cab technologies that the literature, surveys, and interviews did not uncover. The panel also encourages the presentation of the material in specific categories for easier consumption. The panel review ultimately identified six categories for countermeasures. These six general categories of countermeasures are: 1) passive systems, 2) sacrificial systems, 3) active systems, 4) vehicle-based systems, 5) non-physical countermeasures, and 6) other tried strategies and data considerations.

Passive Systems

Passive systems improve driver awareness of bridge and tunnel restrictions through warning signs and enhanced delineation. Warning signs play a vital role in this strategy. By strategically placing clear, well-maintained signage with prominent visuals and easy-to-read text, drivers are alerted to upcoming

limitations. These signs typically highlight crucial information including height and weight restrictions, potential clearance issues associated with lane choices, and any hazardous materials regulations.

Beyond signage, enhanced delineation plays a significant role in improving driver awareness, particularly at night or in low-visibility conditions. This can involve implementing brighter reflective paint on structural elements, installing raised pavement markers that vibrate upon contact, and utilizing strategically placed chevrons or delineator posts to guide drivers along the proper path. By using a combination of these passive systems, IOOS allows their bridges and tunnels to be marked in a more intuitive environment for drivers, ultimately reducing the risk of accidental strikes caused by a lack of awareness, or simply ignorance.

Sacrificial Systems

The purpose of these countermeasures is to reduce structural damage to bridges and tunnels through impact-absorbing systems installed on the face of the structure. This countermeasure is intended to reduce structural damage if a BrTS incident occurs, but often causes significant damage to the colliding OHV.

This approach to mitigating bridge strikes involves the use of impact-absorbing systems directly on the bridge or tunnel structure itself. These countermeasures are not designed to prevent strikes entirely, but rather to lessen the severity of the impact and protect the critical infrastructure. By installing energy-absorbing materials on the underside of bridges or at tunnel entrances, the force of a collision can be distributed and dissipated. While this approach aims to minimize structural damage to the bridge or tunnel, it’s important to acknowledge the potential for significant damage to the OHV involved in the incident.

Active Systems

The purpose of these countermeasures is to improve driver awareness of bridges and tunnels through detection- or location-based warning systems. As opposed to passive approaches, the systems provide immediate response and warning to drivers.

While passive systems like signage and delineation are crucial, active systems offer a more dynamic approach to bridge and tunnel strike prevention. These systems utilize real-time data and driver interaction to create a heightened sense of awareness. A common application uses variable message signs (VMS) positioned before bridge or tunnel entrances. VMS can display real-time clearance information, dynamically adjusting based on weather conditions or potential clearance issues. Additionally, these signs can be programmed to deliver targeted warnings to specific vehicle types exceeding height or weight limitations.

Vehicle-Based Systems

Vehicle bases systems improve driver awareness of bridge and tunnel restrictions through technology. Onboard vehicle detection technology involves strategically placed sensors that communicate infrastructure information with approaching vehicles. The sensors can trigger alerts within the vehicle itself, such as audible or visual warnings on the dashboard, notifying drivers of upcoming clearance restrictions and their vehicle’s compatibility. This real-time interaction provides a crucial reminder to drivers and potentially prompts them to take corrective actions before encountering a potential strike. Vehicle based systems can also include raised bed warnings or load shift warnings for drivers while on their route.

Non-Physical Countermeasures

The purpose of these non-physical countermeasures is to improve driver awareness of bridges and tunnels through institutional policies, load restrictions, permitting procedures, outreach, and driver education programs. Non-physical countermeasures, like institutional policies, permitting procedures, outreach, and driver education programs, are critically important in preventing bridge strikes.

These systems can include several programs and practices that allow for a more holistic approach. Some possible benefits include:

1. Focus on Prevention: Unlike physical barriers that react to an incident, non-physical measures proactively address the root cause – driver unawareness. By educating drivers about limitations and proper procedures, they can avoid strikes altogether. Education and outreach remain vital.
2. Long-Term Impact: Education and outreach have lasting effects. Informed drivers are more likely to be responsible not only on specific bridges and tunnels but also throughout their driving careers. This is increasingly important as there are workforce changes and new technologies coming on the market.
3. Cost-Effectiveness: Compared to the high costs of repairing bridge damage or replacing destroyed vehicles, non-physical measures are a much more cost-effective way to prevent strikes.
4. Universal Application: These measures can be applied to all bridges and tunnels, regardless of location or design, making them a versatile solution.

While physical barriers like impact-absorbing systems have their place, they are often a last line of defense. Non-physical countermeasures address the human element and can significantly reduce the need for such reactive solutions.

Other Data Quality Improvements

The purpose of these strategies is to improve the reliability and accessibility of data used to inform decisions, including the OHV permitting process. For instance, there is a need to accurately describe the load size; the permitting process will not provide an optimal route without accurate load size. There is also a need for complete and up-to-date inventory data for structure size and roadway conditions (e.g., a 3-inch overlay causes a 3-inch reduction in vertical clearance.

Finally, there is a need for accessible data; some states do not provide this readily. There is an opportunity to leverage the use of burgeoning data exchanges to share and broadcast updated information, including information on the location of work zones and related restrictions.

Countermeasures Selected

Ultimately the following countermeasures were identified for inclusion in the Guide. More details on each are provided in the Guide, including any limitations and vulnerabilities associated with those measures. Table 14 below presents the categories and the corresponding selected countermeasures within each category.

Table 14. List of Categories and the Selected Countermeasures

Summary

Selecting the most appropriate countermeasures for BrTS requires a comprehensive approach that goes beyond technical solutions. The developed Guide introduces considerations for countermeasure selection and application. The research team developed a list of countermeasures through a multi-layered approach involving literature review and assessment, community and stakeholder engagement through interviews and surveys, and a formal panel review and revision stage.