Safety and efficiency benefits of traffic signal countdown timers : a driving simulator study

Graduation date: 2015Traffic signal countdown timers (TSCT) are innovative, practical and cost effective technologies with the potential to improve efficiency and safety at signalized intersections. The purpose of these devices is to assist motorists in decision making at signalized intersections with real time signal change information. While successful implementation of these devices is observed internationally, the Manual on Uniform Traffic Control Devices (MUTCD) prohibits the use of TSCT. This research explores the impacts of countdown timers on US drivers; a novel effort not yet conducted.\ud The research methodology includes two experimental media: an online survey, and the driving simulator study. The online survey focuses on driver comprehension of and preferences towards TSCT, whereas the simulator study records driver response to virtual TSCT. The online survey resulted in an overall comprehension rate of 82%, which is reasonably close to the ANSI Z535.3 standard threshold for traffic control devices. The driving simulator study identified benefits regarding safety and efficiency. The presence of red signal countdown timers resulted in 0.72 seconds reduction in the first headway. In presence of green signal countdown timers, driver’s probability to stop at the onset of the circular yellow indication in dilemma zones increases by approximately 13%. These results are suggestive of an improvement in intersection performance, and with proper field validation, the application of TSCT may well be recommended at signalized intersections in Oregon