Guidelines for Traversability of Roadside Slopes
Geometric design practitioners in state transportation agencies have a new set of guidelines on probability of vehicle rollover based on various roadside design features. NCHRP Research Report 911: Guidelines for Traversability of Roadside Slopes will assist practitioners in the reduction of
serious injury crashes associated with rollovers on roadside slopes.
Data from the National Automotive Sampling System (NASS) Crashworthiness Data
System (CDS) shows that one-third of single-vehicle run-off-road (SVROR) crashes result
in rollovers—the leading cause of fatalities in SVROR crashes. Three-quarters of these
rollover crashes involve vehicles digging into the ground on embankments or in ditches
after encroaching onto the roadside. Additionally, according to NASS data, pickup trucks,
utility vehicles, and vans are overrepresented in rollover crashes due to higher centers of gravity. An increase in the percentage of
light trucks in the vehicle fleet necessitates additional research and updates to the roadside
safety guidelines.
The researchers conducted 43,000 simulations for
various combinations of roadside slope configurations and geometric conditions that
represent real-world crash scenarios.
The results helped
to produce this guidance on the traversability of roadside slopes for a variety of roadside
conditions—shoulder width, foreslope, and foreslope width. The guidelines are presented as
probability of vehicle rollover that is defined as a function of various roadside design features.
This Summary Last Modified On: 8/7/2019