SUMMARY

Bridge and Tunnel Strikes: A Guide for Prevention and Mitigation

Bridge and tunnel strikes (BrTS) damage infrastructure, damage vehicles and cargo, create traffic delays, disrupt access to communities, and kill and injure people. For motor carriers, BrTS crashes have the potential to result in insurance increases, safety rating drops, operator termination, and direct responsibility to pay for the cost of repairs.

As highlighted in Figure S-1, there is an average of approximately 14,500 bridge crashes per year nationally, resulting in an average of 220 deaths and 4,700 injuries. Across several years of data, there were 11,000 to 18,000 crashes each year coded as collision with “Bridge Pier or Support, Bridge Rail (includes Parapet), or Bridge Overhead Structure.” These crashes are among the most common causes of bridge failure and cost agencies millions of dollars in infrastructure repairs (Wardhana and Hadipriono 2003; FHWA, n.d.-e; Lee et al. 2013; Cook 2014). Examples include $4 million per year in Virginia and $7 million per year in Texas. Figure S-1 also illustrates three types of BrTS: on-bridge (or in tunnel) collision with superstructure, under-bridge (or entering tunnel) collision with superstructure, and under-bridge (or entering tunnel) collision with substructure.

Challenges Addressing the Issue

The following are three common historical challenges to addressing BrTS risk:

1. Challenges in identifying priority locations: BrTS crashes are underreported and tend to be spread across the network as opposed to clustered at specific locations. The small sample size and low crash density make it challenging to identify and prioritize locations for further diagnosis and potential treatment. There are also data quality issues, including the accuracy and completeness of location coding, contributing factors, and BrTS impact points. This makes it difficult to accurately assign a given crash to a specific bridge or tunnel and to diagnose the factors that contribute to a crash.
2. Challenges in diagnosing contributing factors: BrTS crashes are complex and may involve several diverse contributing factors such as roadway characteristics, bridge or tunnel characteristics, driver and human factors, and vehicle and load factors. Some of these factors are location-specific (e.g., roadway and bridge characteristics), while others could occur randomly (e.g., unsecured load) or propagate throughout the system (e.g., inattentive driver).
3. Challenges in implementing mitigation strategies and enforcing policies: Given the diversity in contributing factors, there is a need for similar diversity in mitigation measures that include engineering, operational, education, and enforcement initiatives. While there are numerous options available to mitigate BrTS risk, an individual strategy may not be sufficient. A combination of countermeasures is often more appropriate to provide redundancy in the system and address the multitude of critical events that can lead to a crash.

Opportunities to Address the Issue

This guide provides methods and information to help agencies and analysts overcome the challenges in mitigating BrTS risk.

1. Identify high-priority locations: The first step to mitigating BrTS risk is to locate each crash to the respective bridge or tunnel. The guide describes various methods for locating crashes as well as the strengths and limitations of those methods. There are also various options for prioritizing bridges and tunnels, including crash-based and risk-based methods. The guide describes the challenges in using traditional crash-based methods and the value of using a risk-based approach to assess the vulnerability of the infrastructure to proactively mitigate BrTS risk.

2. Diagnose BrTS risk and crash contributing factors: Before an agency identifies countermeasures, it is important to understand the factors contributing to BrTS risk. This guide provides an overview of risk-based assessments and a list of common factors that increase BrTS risk. It also includes data collection and analysis procedures that agencies could use to identify jurisdiction-specific risk factors and assess BrTS risk based on state, regional, or local data.
3. Select countermeasures to mitigate BrTS risk: Once an agency identifies BrTS contributing factors, the next step is to identify appropriate countermeasures to target the underlying issue(s). This guide provides a list of common engineering, operational, education, and enforcement policies and strategies to address specific BrTS risk factors. The guide also includes detailed descriptions and information on the applicability, effectiveness, and cost of the various countermeasures. This will help practitioners identify appropriate options to address the issue at hand. The guide provides methods to pare down the initial list of options to the preferred alternative through a more detailed analysis of alternatives. This supports the development of agencywide strategies and procedures to mitigate BrTS risk.
4. Evaluate the effectiveness of investments: The final step is to evaluate projects and programs to understand their effectiveness and return on investment. This guide describes fundamental concepts for tracking and evaluating projects and programs, including measures of effectiveness, methods, and data needs. Agencies may then use the evaluation results to inform future funding and policy decisions. For instance, if new educational or enforcement programs are effective, then law enforcement agencies and motor carriers may choose to continue or expand those programs. Similarly, transportation agencies may choose to implement effective strategies at additional locations or incorporate them as standard practice for future projects.
5. Enhance BrTS data and analysis capabilities: Beyond the analysis of jurisdiction-specific issues, there is a need for agencies to provide accessible data and information for external users. This guide describes opportunities for agencies to contribute data to improve the completeness, accuracy, and accessibility of a comprehensive and up-to-date inventory of BrTS data through a BrTS Clearinghouse. This will support national efforts such as cross-jurisdiction truck routing, BrTS research, and BrTS tracking and reporting. Given complete and quality data, a national BrTS Clearinghouse can provide estimates of the risk (i.e., likelihood and consequences) of a BrTS crash based on bridge, tunnel, roadway, and operational characteristics. Transportation agencies can use this information to identify roadway, bridge, and tunnel locations for potential infrastructure improvement projects. Commercial motor vehicle enforcement officials can use this information to identify risk factors and potential locations for implementing enforcement strategies. Motor carriers can use this information to identify routes that are higher risk and instruct their drivers to avoid such routes. Researchers can use the BrTS Clearinghouse to advance the state of the practice for identifying and mitigating BrTS risk.

In summary, the objective of this guide is to assist transportation agencies, motor carriers, and practitioners in preventing and mitigating BrTS risk. This guide will help agencies and analysts identify high-priority locations, diagnose factors contributing to BrTS risk, select and prioritize countermeasures, and evaluate the effectiveness of projects and programs. By quantifying BrTS risk and considering safety alongside other factors, agencies will better understand the comprehensive costs and benefits of projects, which will lead to more informed decisions and impactful investments. The guide also supports the development and application of a national BrTS Clearinghouse that will support researchers in advancing the state of the practice and will support practitioners in implementing effective programs and policies for mitigating BrTS risk.