Improving Safety at Signalized Intersections During Inclement Weather Conditions - A Real-Time Weather-Responsive System
Adverse weather conditions such as rain and snow can reduce pavement friction and visibility distance, impairing the ability of drivers to operate their vehicles safely, reducing roadway capacity and significantly affecting system efficiency. Several empirical studies in the literature have investigated the effect of inclement weather on various signal timing traffic parameters. In terms of weather effect on highway safety, several studies found that weather significantly increases crash risk. Weather-related crash fatalities account for 17 percent of all traffic fatalities each year. One study suggests that snow increases crash risk by approximately 120, 80, 40, and 40 percent for minimal, minor, major, and fatal injuries, respectively. Existing studies collectively show that traffic signal timing used under normal conditions becomes problematic under adverse weather for two primary reasons. First, reductions in average speeds and saturation flow rates and the increase in start-up delays make normal signal timing unsuitable during inclement weather. Second, with reduced pavement friction and visibility, default all-red and yellow clearance intervals become unsafe as motorists are more likely to be trapped in dilemma zones. The goal of this project is to develop and implement a real-time weather-responsive traffic signal control system for the state of Idaho with the intent to improve the efficiency and safety of traffic signal operations during inclement weather. This system will receive and use weather information from the FHWA’s Clarus weather data system and from the state’s Road Weather Information Stations (RWIS) to adapt signal timing in response to inclement weather. Five innovations are necessary to fully achieve the proposed project goal. First, the system will operate and achieve its potential using current traffic controller and controller cabinet technologies. Second, the system will be compatible with future applications within the Federal Highway Administration’s connected-vehicle initiative. Third, minimal hardware, in addition to traffic controllers, will be required for full implementation. Fourth, computer driven algorithms will implement traffic signal control decisions using Clarus data. Fifth, software design will incorporate self diagnostic techniques for fault detection and recovery to maximize security and survivability and minimize cost.