SUMMARY REPORT ON SELECTED GUARDRAILS. FINAL REPORT

This report summarizes the crash test results as well as the construction, maintenance, and accident experience observed for three types of guardrails: the modified South Dakota 3-cable guardrail, the modified Minnesota 3-cable guardrail and the modified thrie beam guardrail. The modified South Dakota 3-cable guardrail is similar to the standard G1 cable guardrail except that a lighter, less expensive 4-lbs per foot flange-channel post is used instead of the standard S3x5.7 post. The modified Minnesota 3-cable guardrail uses a closer post spacing and wooden posts with a weakening hole. This hole helps minimize the chance of causing a small car to roll over. The modified thrie beam guardrail is a variation of the standard G9 thrie beam guardrail. It uses a unique guardrail blockout that helps improve the barrier performance in large vehicle collisions. The development of these systems is summarized and the basic design principals are explained. Where available, construction, cost, and accident data are presented from states that have used these systems.