Sight-Distance Requirements for Left-Turning Vehicles at Two-Way Stop-Controlled Intersections

Abstract

The current highway geometric design guide provides a method for calculating intersection sight distance at two-way stop-controlled intersections by assuming that a departing driver on the minor road that would start from a resting position needs a fixed-time gap for departing the intersection regardless of the design speed or the grade on the major road. However, departing drivers may fail to perceive the speeds of the approaching vehicles on the major road in order to judge the available departure gap and decide whether or not to accept it. In this paper, a novel method is introduced to determine intersection sight distance requirements for two-way stop-controlled intersections based on actual drivers’ behavior and vehicle capabilities. The method incorporates acceleration profiles for vehicles starting from rest, which were developed based on field data collected using global positioning system (GPS) data loggers that recorded the positions (latitudes, longitudes, and altitudes) and the instantaneous speeds of different vehicle types piloted by different drivers at 1 s intervals. Design tables and an application example are presented to help designers select the required intersection sight distance based on the design speed and the grade on the major road.