Evaluating the Benefits of Slope Rounding (Prepared for Minnesota DOT, Research Study No. 0468F.) (0468F-1F)

This study addressed the problem of evaluating the benefits of rounding the hinge at the intersection of the shoulder and side slope. While it is generally believed that slope rounding enhances roadside safety, no studies have been made to quantify or estimate its benefits. With the problems ever-increasing highway construction costs and limited funding, it is important that a cost-effectiveness analysis be conducted to aid in the decision-making policy. The study approach consisted of (a) identification of parameters to be evaluated, (b) HVOSM computer simulations to evaluate occupant risk on the rounded and unrounded side slopes, (c) benefit/cost (B/C) analysis of rounded versus unrounded side slopes, and (d) development of slope rounding guidelines. In the initial part of the study a sensitivity study was conducted to identify key parameters. The HVOSM computer simulation program was used to evaluate occupant risks associated with encroachments on unrounded and rounded side slopes of 6:1, 4:1, and 3:1. The B/C analysis was applied to evaluate unrounded and three types of rounded treatments. Results of the B/C analysis were used to develop recommended slope rounding guidelines for freeways and rural arterials.