Citation

Post ER, McCoy PT, Wipf TJ, Ruby RJ. Transp. Res. Rec. 1980; 769: 37-43.

Copyright

(Copyright © 1980, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

A study of the performance characteristics of two guardrail-bridgerail transition systems is reported. The two systems were the American Association of Highway and Transportation Officials (AASHTO) stiff-post system and the Nebraska Department of Roads (NDR) "double W-beam" system. The AASHTO system provides larger-sized posts on reduced spacings, whereas the NDR system uses another length of guardrail alongside the face of the existing guardrail with uniform 1.01-m (6-ft 3-in) post spacings. The NDR system eliminates the difficulty of increasing the stiffness of existing systems because of the concrete bridge abutments and/or wing walls that restrict the placement of additional posts on reduced spacings. The objective of the study, which was limited in scope, was to use the BARRIER VII computer program to compare the cost-effectiveness of the two systems. The study considered the effects of impacts with the guardrail transitions by two different-sized automobiles under all possible combinations of speed and angle. The findings show that a reasonable doubt exists as to the cost-effectiveness of the AASHTO system under a wide range of impact conditions. Specifically, the stiff-post system produced more injury-type accidents and resulted in larger exit angles, which increased concern about secondary collisions with other vehicles. The structural adequacy of the guardrail-bridgerail connection in both systems was the single most important design element.