BACKGROUND
The AASHTO Manual for Assessing Safety Hardware (MASH) specifies impact speeds for crash testing and evaluation of barrier systems such as guardrails, median barriers, and bridge rails. The highest impact speed defined by MASH for passenger vehicles is 62 mph. This impact speed was derived from analyses of reconstructed crash data that is nearly 20 years old.
Currently, 18 states have posted speed limits of 75 mph or higher. Seven of these states have posted speed limits of 80 mph, and one state has posted speed limits of 85 mph. With most of these states adopting such higher speeds within the past 5 years, there is a growing need for evaluating barriers at higher impact speeds to maintain appropriate barrier performance.
Increased impact speeds will place more demand on barrier systems. The performance limits of current barrier systems beyond the MASH design impact speed of 62 mph are not fully understood. Partial rail tears have been observed in guardrail systems tested under MASH impact conditions, indicating that these systems are near containment capacity. Research to assess performance limits of existing barrier systems for greater impact speeds is needed.
OBJECTIVES
The objectives of this research are the following:
1. Assess the performance of existing, non-proprietary longitudinal barriers on roadways with posted speeds of 75 mph and higher.
2. Identify needs for barrier test criteria at these higher speeds.
3. Develop, as needed, barrier test parameters that could be considered for future criteria and crash testing. At a minimum, these parameters shall include test vehicles, impact speed, angle of impact, and required impact results.
4. Develop cost-effective barrier design(s) to meet the developed test parameters and verify performance of the design(s).
This research shall evaluate existing, non-propriety barrier designs and exclude proprietary barrier, transition, and terminal designs.
