Citation

Gattis J, Duncan L. Transp. Res. Rec. 2009; 2092: 66-74.

Copyright

(Copyright © 2009, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.3141/2092-08

PMID

unavailable

Abstract

This paper describes the findings from a study that examined differences in speeds and elapsed travel times among vehicles turning right and turning left into driveways with flatter, moderate, and steeper vertical alignments or profiles. All driveways were located on built-up suburban multilane arterial roadways with either a separate left-turn lane or a two-way left-turn lane, and with posted speeds of 40 or 45 mph. All were commercial driveways with a radius of 13 to 19.5 ft. The main variable among the three groups of driveways was the gradient. The vehicle speeds and elapsed travel times among driveways with flatter, moderate, and steeper grades were found to vary slightly. The inferred side friction values for the faster-turning vehicles were similar to those listed in the 2004 Green Book. The findings have application to the safety of bicyclists, motorists, and pedestrians concerned about speeds of vehicles turning right or left into driveways. From these findings, one can infer design speeds for the entry of driveways similar to the ones studied. The findings could also affect estimates of gap acceptance and capacity at unsignalized driveway connections.