Citation

Asadollahi Pajouh M, Julin RD, Stolle CS, Reid JD, Faller RK. Traffic Injury Prev. 2018; 19(2): 219-224.

Affiliation

Midwest Roadside Safety Facility, University of Nebraska-Lincoln 130 Whittier Research Center, 2200 Vine Street, Lincoln , Nebraska 68583-0853 , Phone, Email: rfaller1@unl.edu.

Copyright

(Copyright © 2018, Informa - Taylor and Francis Group)

DOI

10.1080/15389588.2017.1353687

PMID

28696773

Abstract

OBJECTIVE: Guardrail heights play a crucial role in the way that errant vehicles interact with roadside barriers. Low rail heights increase the propensity of vehicle rollover and override, while excessively-tall rails promote underride. Further, rail mounting heights and post embedment depths may be altered by variations in roadside terrain. An increased guardrail height may be desirable to accommodate construction tolerances, soil erosion, frost heave, and future roadway overlays. This study aimed to investigate and identify a maximum safe installation height for the Midwest Guardrail System, which would be robust and remain crashworthy before and after pavement overlays.

METHODS: A research investigation was performed to evaluate the safety performance of increased mounting heights for the standard 787-mm (31-in.) tall, Midwest Guardrail System (MGS) through crash testing and computer simulation. Two full-scale crash tests with small passenger cars were performed on the MGS with top-rail mounting heights of 864 mm and 914 mm (34 in. and 36 in.). Test results were then used to calibrate computer simulation models.

RESULTS: In first test, a small car impacted the MGS with 864-mm (34-in.) rail height at 102 km/h (63.6 mph) and 25.0 degrees and was successfully redirected. In second test, another small car impacted the MGS with a 914-mm (36-in.) rail height at 103 km/h (64.1 mph) and 25.6 degrees and was successful. Both system heights satisfied the Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) evaluation criteria. Test results were then used to calibrate computer simulation models. A mounting height of 36 in. was determined to be the maximum guardrail height that would safety contain and redirect small car vehicles. Simulations confirmed that taller guardrail heights (i.e., 37 in.) would likely result in small car underride. Also, simulation results indicated that passenger vehicle models were successfully contained by the 34-in and 36-in. tall MGS installed on approach slopes as steep as 6:1.

CONCLUSIONS: A mounting height of 914 mm (36 in.) was determined to be the maximum guardrail height that would safety contain and redirect 1100C vehicles and not allow underride or excessive vehicle snag on support posts. Recommendations were also provided regarding the safety performance of the increased-height MGS.

Language: en

Keywords

Crash Testing; Finite Elements and Guardrails; Highway Safety; Maximum Height; Roadside Hardware