Examining Optimal Sight Distances at Rural Intersections

Decisions made regarding driver sight distance at rural intersections are complex and require considerations for safety; efficiency; and environmental factors. Sight distance; cross-traffic velocity; and vehicle placements significantly affect driver judgment and behavior at these intersections. A series of rural; two-lane thru-STOP simulated intersections with differing sight distances and traffic speeds were created and then validated by county and state engineers. Experimental data from 36 participants in a time-to-collision (TTC) intersection crossing judgment task and a rural highway thru-STOP intersection driving simulation task was analyzed to clarify the influence of rural thru-STOP intersection characteristics on driving performance and decision-making. Results demonstrated that longer sight distances of1;000 ft. and slower crossing speeds (i.e.; 55 mph) were more accommodating for participants attempting to select gaps and cross from the minor road; corresponding with (1) lower mental workload; perceived risk; difficulty; and anxiousness; and (2) better performance in terms of estimated crash rate; and larger TTCs. Second; longer distances of 1;000 ft. appear to aid drivers' responsiveness on the main road approaching an intersection; specifically when another driver on the minor road runs the stop sign. Minor road drivers positioned close to the roadway at the stop sign; compared to standard stop bar placement; tended to help reduce the speed of main road drivers. Overall;results demonstrated a systematic improvement in the performance of both minor and major road drivers with the implementation of a1;000-foot sight distance at rural thru-STOP intersections.