Analysis of Driver Behavior in Dilemma Zones at Signalized Intersections

Abstract

A field study evaluated the stopping characteristics of vehicles 2.5 to 5.5 s upstream of signalized intersections at the start of a yellow interval, a region typically considered drivers' indecision zone or dilemma zone. Characteristics included brake-response times for first-to-stop vehicles, deceleration rates for first-to-stop vehicles, distinguishing characteristics and prediction of first-to-stop versus last-to-go events, and distinguishing characteristics and prediction of red-light-running events. Consumer-grade video cameras temporarily installed at four high-speed and two low-speed intersections in the Madison, Wisconsin, area recorded dilemma zone vehicles. Several factors were measured for each last-to-go (n = 435) and first-to-stop (n = 463) vehicle in each lane during each yellow interval, including approach speed; distance upstream at start of yellow; brake-response time; deceleration rate; vehicle type; headway; tailway; action of vehicles in adjacent lanes; presence of side-street vehicles, pedestrians, bicycles, or opposing vehicles waiting to turn left; flow rate; length of yellow interval; and cycle length. The observed 15th, 50th, and 85th percentile brake-response times for first-to-stop vehicles were 0.7, 1.0, and 1.6 s, respectively; their observed deceleration rates were 7.2, 9.9, and 12.9 ft/s2, respectively. Vehicles were more likely to go through than to stop under the following conditions: shorter estimated travel time to intersection at start of yellow; longer yellow interval; the subject was a heavy vehicle (truck, bus, recreational vehicle); absence of side-street vehicles, bicycles, pedestrians, and opposing left-turn vehicles; and presence of vehicles in adjacent lanes that went through. Heavy vehicles were more likely than passenger vehicles to run a red light. Vehicles were more likely to run a red light when vehicles in adjacent lanes that also went through were present and when side-street vehicles, bicycles, pedestrians, and opposing left-turn vehicles were absent.