ROLLOVER POTENTIAL OF VEHICLES ON EMBANKMENTS, SIDESLOPES AND OTHER ROADSIDE FEATURES. VOLUME II: TECHNICAL REPORT. FINAL REPORT

The objective of this research program was to study the interaction of vehicles with various roadside features to determine critical roadside-feature design criteria based on the potential for inducing vehicle rollover. Results of a review of accident data analyses reported in the literature are presented to indicate the general state of knowledge of rollover accidents. Among the findings are that: (1) different classes of vehicles based on use and/or size exhibit distinct differences in rollover tendencies, and (2) the existing accident data base lacks the information necessary to define the roadside-feature geometry and other conditions that caused vehicle rollover. Full-scale tests with an instrumented automobile were performed to verify the HVOSM (Highway-Vehicle-Object Simulation Model) as modified to improve its utility for studying vehicle off-road traversals. The HVOSM was then used to predict the dynamic responses of representative small and large cars encountering different roadside-feature configurations, including both tracking and nontracking departures from the roadway. It is shown that the sideslope of fill embankments should not exceed 3:1, regardless of the height of the embankment, to reduce the likelihood of small-car rollover. It is recommended that present AASHTO design criteria for barrier warrants be revised accordingly. It is also shown that the rounding of slope breaks currently recommended by AASHTO further reduces the rollover hazard. This report consists of two volumes. The other volume is Volume I, Executive Summary.