BACKGROUND
Each year, roadway departure crashes in the United States result in serious injuries and fatalities. Side impacts of vehicles into roadside hardware are a growing public safety problem. In particular, side impacts with guardrail account for a significant percentage of fatalities in passenger vehicle-guardrail crashes.
An occupant of a passenger vehicle that side impacts with guardrail has a 30 percent higher probability of fatal injury than an occupant of a car that frontally impacts with guardrail. Many roadside safety features, such as terminals, guardrail end treatments, crash cushions, and luminaire and sign supports, are designed to break away under typical loads for a frontal impact. However, side impacts by non-tracking vehicles may not have enough force to engage the breakaway mechanisms of these features. Because the side of a vehicle, unlike the front, has less structure and crumple zone, side impacts can result in especially severe injuries.
To date, however, no substantive improvements have been made to the performance of roadside safety features during vehicle side impacts. NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features provided information on side impacts through test and evaluation procedures; however, it does not contain recommendations or requirements for side impact crash testing of roadside safety hardware (RSH). More recently, the NCHRP Report 350 appendix for side impact test and evaluation procedures was not included in the AASHTO Manual for Assessing Safety Hardware (MASH) crash test procedures. Little is known about how NCHRP Report 350- or MASH-compliant hardware performs in side impact crashes.
No research to date has developed a comprehensive approach for evaluating RSH under side impact conditions. The development of methods for evaluating these crashes would lead to improvements in RSH and improved safety for motorists. Results of this research could enable transportation agencies to establish levels of safety risk and use quantitative information to do so.
Under NCHRP Project 22-32, “Development of Methods to Evaluate Side Impacts for Next Edition MASH,” work began to develop this comprehensive approach and produced a report describing the following:
- Recommended test procedures for evaluating RSH under side impact conditions;
- Plan for validating two aspects of side impact performance: ability of side impact design improvements to lower occupant risk and translation of lower occupant risk to fewer severe and fatal injuries in side impact crashes observed in the field;
- Preliminary recommendations for consideration by AASHTO in future updates of MASH and Roadside Design Guide (RDG); and
- Work plan for side impact crash testing and finalizing side impact test procedures and evaluation criteria, with optional side impact crash testing of luminaire supports and shallow-angle corner impacts on guardrail.
The crash testing, however, was not conducted, hence the need for additional research, with the intention of this testing to include luminaire supports and shallow-angle corner impacts on guardrail.
OBJECTIVES
The objectives of this research are the following:
- Determine appropriate values for RSH performance criteria, building on previously developed test procedures; and
- Develop an evaluation guide for RSH under side impact conditions.
This research shall consider appropriate test vehicles and focus on terminals; however, it shall also consider additional roadside safety devices.
STATUS: Research in progress.
