Modeling the Risk of Wrong-Way Driving Entry at the Exit Ramp Terminals of Full Diamond Interchanges

Abstract

Wrong-way driving (WWD) crashes are a critical safety issue on freeways. Although these crashes are rare and random in nature, they often result in severe injuries and/or fatalities. Typically, exit ramp terminals are the initial point of entry for wrong-way (WW) drivers on freeways. Therefore, it is important for transportation agencies to identify the exit ramp terminals with higher possibility of WW entries and apply safety countermeasures to reduce the chances of their occurrence. However, the random nature of WWD crashes and the difficulty in identifying the actual entry points makes it hard for transportation agencies to assess the risk of WWD at a particular exit ramp terminal and apply countermeasures accordingly. This study developed mathematical models for predicting the risk of WW entries at the exit ramp terminals of full diamond interchanges. The geometric design features, usage of traffic control devices, area type where the interchanges are located, and annual average daily traffic (AADT) at the exit ramp terminals with or without history of WWD were used as potential predictors of WW entry. Transportation agencies can use these models to assess the risk of WW entries at the exit ramp terminals within their jurisdictions and consider possible countermeasures. They also can be applied during the design phase to determine the combination of geometric design features and traffic control devices that ensures the least possibility of WW entry.

Comparative Analysis of Freeway Exit Ramp Terminal Design Practices to Deter Wrong-Way Driving in Different States

“…Such use of WW signs close to exit ramp terminals can be associated with clear visibility and less likelihood of causing driver confusion. The authors' previous work reported that the probability of WWD increases by approximately 4.5 times when the distance of the first WW sign is more 200 ft from the crossroad (10,11).…”

“…Previous studies reported numerous safety countermeasures to reduce the chances of WW entry at the exit ramp terminals of freeway interchanges. Collectively, these safety countermeasures can be divided into three categories: (a) geometric design features (6)(7)(8)(9)(10)(11); (b) application of TCDs (7,(10)(11)(12)(13)(14); and (c) application of intelligent transportation systems. Based on the focus of this study, the following paragraphs discuss the recommended guidelines for geometric design features and application of TCDs to deter WW entry at the exit ramp terminals.…”

“…The use of WW arrows, in addition to the lane use marking, is also recommended (12). The application of WW signs beyond 200 ft along the exit ramps from the crossroad increases the probability of WWD by approximately 4.5 times (10,11). Furthermore, the signalized exit ramp terminals provide more regulated traffic flow and are likely to reduce the occurrence of WW entries.…”

“…Based on the previous studies and available guidelines, the following geometric features are reported to have a significant effect on the occurrence of WW entries at full diamond interchanges: intersection angle, type of median on crossroad, type of channelizing island, distance of nearest access point, and corner radius (6-8, 10, 11). Similarly, for partial cloverleaf interchanges, the following geometric characteristics are reported to have a significant effect on the occurrence of WW entries: intersection angle, corner radius from crossroad to entrance ramp, corner radius from exit ramp to crossroad, type of median on crossroad, type of median between entrance and exit ramp, width of median between entrance and exit ramp, type of channelizing island, distance of nearest access point, and intersection balance (6)(7)(8)(9)(10)(11). Therefore, these geometric design features were collected from the Google Earth Aerial and Street View imagery for the exit ramp terminals in both states.…”

“…WWD crashes can often be linked to driving under the influence of alcohol or drugs as well as age related impairments (2)(3)(4)(5), which cannot be eliminated by applying engineering countermeasures alone. Nonetheless, good geometric design of exit ramp terminals and proper use of wrong-way (WW) related traffic control devices (TCDs) can be helpful to reduce these crashes (6)(7)(8)(9)(10)(11).…”