Background: Recent roadside safety research has indicated that increased variation in the size, weight, characteristics, and shape of vehicles in the U.S. vehicle fleet is raising concerns that existing barriers, related hardware, and other features may not fulfill all their safety functions. These concerns suggest a need for improved compatibility between the vehicle and the roadside safety hardware, but increased compatibility is not likely to occur effectively under current practices for the design of roadway facilities and vehicles.

Currently, developers of roadside safety hardware are guided by testing requirements using a range of vehicles defined by NCHRP Report 350, "Recommended Procedures for the Safety Performance Evaluation of Highway Features." Historically, these testing requirements have been updated only once every 10 to 12 years. Therefore, changes in the nation's vehicle fleet (e.g., increased use of light trucks and vans [LTV], aerodynamic vehicle shapes, increased use of composite materials and light weight plastics in vehicle manufacture) may not be reflected in the design of roadside safety hardware in a timely manner. The auto industry designs new vehicles to meet Federal Motor Vehicle Safety Standards (FMVSS). These safety standards are significantly different from those used to test and qualify roadside safety hardware. The FMVSS are regularly updated when safety problems or new technological options to increase safety are recognized, but the results of FMVSS testing are not used in the evaluation of roadside safety hardware.

There are similarities and differences in the approaches used for the design of safe roadside hardware and vehicles. For example, both groups use the analysis of accident data to monitor safety, and they evaluate impact performance through the use of computer modeling and full-scale crash testing. However, differences are apparent in the nature of tests, the rate of design change, evaluation criteria, instrumentation, and other factors. Both industries face the challenges of strong competition and the need to meet consumer and public demands. Ideally, communication between the various groups would help ensure the compatibility of vehicles and roadside safety hardware.

Recent crash testing has revealed that vehicle incompatibilities can lead to undesirable results, such as vaulting, underriding, or snagging barriers, loss of vehicle components (e.g., front wheel) critical to maintaining stability, and/or rolling over. It has also been recognized that some roadside safety hardware designs counteract vehicle safety systems. For example, crash cushions may absorb enough crash energy to delay air bag deployment.

Reducing the incompatibilities between vehicles and roadside safety hardware will not be easy. There is an extensive existing roadside safety infrastructure, and millions of vehicles in the fleet that would be extremely costly to retrofit to improve safety. However, a common interest exists between the designers of vehicles and roadside hardware in improving highway safety, and the continual turn over of vehicles and hardware provides an opportunity to improve future compatibility. Research is needed to identify and quantify compatibility issues across the full spectrum of current and future vehicle types and roadside safety hardware. Further, the need exists to define and evaluate the range of options for addressing incompatibilities that have negative effects on highway safety.

Objective: The objectives of this research were to (1) improve the understanding of the compatibility between vehicles and roadside safety hardware, (2) assess opportunities and impediments to improving compatibility, (3) establish a process for future assessment of compatibility, and (4) recommend strategies and tactics that will lead to improved compatibility. This effort is expected to focus on the full range of passenger vehicles, but be expandable to other types of vehicles.

Tasks: The tasks envisioned for this project included the following: (1) Review the literature (including foreign documents) to identify compatibility issues, characteristics, and trends of the vehicle fleet and roadside safety hardware; crash testing and safety analyses; and possible approaches to improving compatibility. Review crash test film and data to gather initial evidence of incompatibility. Review the FMVSS to identify elements that may have relevance to impacts with roadside safety hardware. Review the objectives and findings of recent and ongoing, relevant research by FHWA, NHTSA, NCHRP, and others. (2) Identify the common roadside safety hardware types based upon current practices and guidelines. Gather information to establish a representative inventory of roadside safety hardware to aid in establishing estimates of the magnitude of the problem and the factors influencing it. Describe possible future changes to roadside safety hardware designs and usage guidelines using expert opinion. (3) Describe the characteristics of vehicles that are critical to crashes with roadside safety hardware. Describe the composition of the current fleet and changes over time. Project the future vehicle fleet characteristics and potential changes to the FMVSS. (4) Establish a process for systematic review of full-scale crash test results conducted for vehicle and roadside safety hardware design. The process should be geared to identify incompatibilities that lead to negative safety impacts--for example, desired vehicle frontal area needed to interact with roadside safety hardware, bumper height and stiffness requirements for smooth redirection, and influence of center-of-gravity height on propensity to roll. The process should be structured to capture multiple perspectives (e.g., vehicle designers, hardware designers, regulatory agencies, and researchers) on incompatibilities. Conduct a pilot review of full-scale crash test results using the process to identify common occurrences that reflect incompatibility. (5) Determine the feasibility of gathering information that will allow verification and quantification of the incompatibilities using data from reported real-world accidents as documented in police reports, DOT accident data, in-service evaluations, accident reconstructions, or other sources. Conduct a pilot study to demonstrate the effectiveness of the methodology for gathering information determined to be most feasible. Indicate how the inferences drawn from these data would be used to verify specific vehicle and hardware incompatibilities and to quantify the extent of the problem. (6) Identify the various perspectives on compatibility issues through contacts with selected highway agencies, FHWA, NHTSA, vehicle and roadside safety hardware manufacturers, trade associations, and other domestic and international organizations. Review the findings of Tasks 1 through 5 with persons involved in vehicle design and safety certification. The contractor will be expected to emphasize contacts with the automotive industry at their meetings or forums. The contractor may wish to select 6 to 12 persons identified through these contacts to serve in an advisory capacity in the remaining task efforts. (7) Prepare an interim report that summarizes the findings of Tasks 1 through 6 and provides detailed outlines for the efforts to be undertaken in the second phase of the project. Participate in an interim meeting with the project panel to review the findings and finalize plans for the remaining project tasks. At the interim meeting, the panel will approve the specific scope of the vehicle fleet and roadside safety hardware to be studied in this project. (8) Conduct further detailed investigations of full-scale crash tests following the methods (developed in Task 4) approved by the panel at the interim meeting. Implement procedures to assure data quality and provide periodic reporting. (9) Gather additional real-world accident data and analyze it following the methods (developed in Task 5) approved by the panel at the interim meeting. Implement procedures to assure data quality and provide periodic reporting. (10) Conceptualize a process for evaluating compatibility that can be applied in the design and evaluation of vehicles and roadside safety hardware. Consider the use of analytical, simulation, and crash-testing methods as part of the process. Prepare a prototype of this process for assessment of its feasibility and demonstrate its applicability in at least two case studies. (11) Identify strategies and tactics to improve the compatibility of vehicles and roadside safety hardware and present these in a format that categorizes similar approaches. These may include the development of appropriate roadside hardware designs and specifications, modification of vehicle safety certification tests, and revision of vehicle performance standards. The search for options should attempt to recognize where positive effects can be achieved for multiple purposes (e.g., improved compatibility of bumper heights is important to vehicle-to-vehicle as well as vehicle-to-hardware crashes). Identify constraints (e.g., legal, institutional, economic, political) that may prevent the use of information regarding vehicle design and roadside safety hardware trends and incompatibilities. Recommend method(s) for overcoming these constraints and develop a plan for implementing recommendations. (12) Prepare a second interim report that summarizes the findings of Tasks 8 through 11 and provides detailed outlines for the efforts to be undertaken in the final phase of the project. (13) Assess the feasibility of various approaches to reduce incompatibility problems identified in Task 11. Evaluate the costs and benefits associated with measures to improve the compatibility of vehicles and roadside safety hardware. (14) Organize and conduct a workshop of safety-hardware and vehicle-design professionals to solicit feedback on the findings of the research and to initiate interactions that will lead to improved compatibility. At the workshop, discuss the nature of future vehicle characteristics in relation to roadside safety hardware and the expected impact on safety. Analyze potential changes in technology affecting roadside hardware and design. The contractor will be expected to document the discussions and conclusions reached at the workshop and make recommendations for changes to the project reports and processes resulting from the research. (15) Prepare a final report that documents the research efforts and findings. The contractor will also be expected to prepare up to five topical summaries from the research results that can be used to increase awareness of the problem and opportunities for addressing it among vehicle and hardware manufacturers, DOT staff, and other transportation professionals.

Status: The project has been completed.

Product Availability: The final report is available online as NCHRP Web Document 61.