SAFETY OF DRIVEWAYS IN CLOSE PROXIMITY TO EACH OTHER

Preliminary guidelines were developed for minimum spacing of driveways on high speed roadways. The guidelines address safety concerns related to ran-off-the-road accidents. The purpose of the guidelines is to minimize the risk to an errant motorist who leaves the road, crosses a driveway/sloped end culvert, and then becomes airborne. It is desirable to have a safe recovery area downstream from the driveway--one that is free of hazardous features, including another driveway. This study was intended to be a two-year study, with the effort in the first year concentrating on a summary of existing practices and accident experience throughout Texas and other state departments of transportation. Work in the second year was to fill voids in the data found in the first year's work. Very little substantive data were found through surveys of state practices and through accident data. A limited computer simulation study was conducted with the Highway-Vehicle-Object-Simulation-Model (HVOSM) to gain insight into vehicular behavior upon crossing a driveway. Use of HVOSM provided data from which preliminary spacing criteria could be developed. Funding for the second year's work was not approved, and hence more comprehensive guidelines were not developed.