From 2007 through 2009, there were over 14,000 fatalities that resulted from opposite direction crashes (source: Fatal Analysis Reporting System, NHTSA). Nearly 80% of these crashes occurred on undivided roadways. Countermeasures, such as rumble strips/stripes, delineators, and barriers have proven to reduce both total crashes and serious injury crashes as reported in NCHRP Report 641; however there is limited guidance on their specific performance. Improved guidance is needed on when and what type of countermeasure is appropriate, and what roadway factors may lead to higher opposite direction crash frequency rates. Additionally, guidance on progression of countermeasures (i.e., from rumble strips/stripes to additional separation to addition of barriers) and how these countermeasures could be applied on a systemic basis to proactively address opposite direction crashes is not well documented in AASHTO guidance. Although many opposite direction crash countermeasures have been studied individually, guidance on selecting from a wide range of opposite direction countermeasures does not exist. Median barrier for divided roads and centerline rumble strips for undivided roads have been the most studied countermeasures, but other countermeasures, such as reallocating lane width to create a small buffer median between opposing lanes, may be appropriate in some applications. A comprehensive guide on opposite direction crash countermeasures combined with a better understanding of what roadway factors increase opposite direction crash risk would aid transportation agencies to cost-effectively invest in countermeasures to reduce crashes on their road systems.
The objective of this research was to develop a guidance document for the identification, prioritization, and selection of effective countermeasures to reduce or eliminate opposite directional crashes. For the purpose of this research, the focus is for 2-lane undivided roadways. However, results may have application to other types of undivided roadways and shall be noted.
The guidance document is intended for future possible adoption by the AASHTO Technical Committee on Roadside Safety as an update to the AASHTO Roadside Design Guide
. The guidance document addresses: 1) Locations and roadway factors that influence the frequency of opposite direction crashes, such as but not limited to average daily traffic (ADT), geometric features (e.g., tangents, horizontal and vertical curves, cross-sectional features), topography, geographical areas, and operating speeds; 2) Selection of countermeasures (low and high cost) that can be implemented individually or in combination, such as but not limited to: rumble strips/stripes, delineators, raised pavement markings, separation between opposing lanes, and barriers. Identify countermeasure effectiveness under various roadway factors; and 3) Any adverse impacts that may result from implementation of the countermeasures such as an increase of other crash types, operational impacts, and if the countermeasures impact other road users (such as bicyclists and motorcyclists) as well as adjacent properties (e.g., noise from rumble strips/stripes and surface treatments).
Research is complete. Final Report is under review