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Rail height effects on safety performance of Midwest Guardrail System
Mojdeh Asadollahi Pajouh1, Ramen D Julin2, Cody S Stolle1
1a Midwest Roadside Safety Facility , University of Nebraska-Lincoln , Lincoln , Nebraska.
Traffic Injury Prevention
|July 12, 2017
Summary
The Midwest Guardrail System (MGS) remains crashworthy at increased heights up to 36 inches. Taller guardrails may cause vehicle underride, but 36-inch MGS safely contains vehicles on steep slopes.
Area of Science:
- Roadway safety engineering
- Traffic engineering
- Vehicle dynamics
Background:
- Guardrail height is critical for vehicle interaction, with low heights causing rollovers and high heights causing underride.
- Roadside terrain variations can affect guardrail mounting heights and post embedment.
- Increased guardrail height is often needed for construction tolerances, erosion, frost heave, and future pavement overlays.
Purpose of the Study:
- To determine the maximum safe installation height for the Midwest Guardrail System (MGS).
- To ensure the MGS remains crashworthy at increased heights, even after pavement overlays.
- To evaluate the impact of increased guardrail height on vehicle interaction and safety performance.
Main Methods:
- Conducted two full-scale crash tests on MGS with 34-inch and 36-inch top-rail mounting heights using small passenger cars.
- Utilized crash test results to calibrate computer simulation models for further analysis.
- Evaluated MGS performance against Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) criteria.
Main Results:
- Both 34-inch and 36-inch MGS heights successfully redirected small passenger cars in full-scale crash tests.
- The 36-inch MGS met MASH TL-3 criteria, with simulations indicating potential for small car underride at 37-inch heights.
- Simulations showed the 34- and 36-inch MGS could contain vehicles on approach slopes as steep as 6:1.
Conclusions:
- A 36-inch (914 mm) mounting height is the maximum safe height for the MGS to contain and redirect 1100C vehicles.
- This height prevents vehicle underride and excessive snagging on support posts.
- Recommendations are provided for the safe performance of MGS with increased mounting heights.
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