Implementation of High Accuracy Radar Detectors for Traffic Safety Countermeasure Evaluation

Abstract

Rural roadways account for a significant portion of fatal crashes in the United States despite carrying lower total vehicle miles traveled than urban roads. An important contributor to this is excessive speeds at horizontal and vertical curves. While geometric design has established norms for handling these curves, the message is still often difficult to communicate to drivers. Recent technologies have been developed to enhance this communication on horizontal curves; however, treatments for vertical curves have not yet experienced similar advancements. A new approach, involving chevron signs, is being considered by Washington County, Minnesota. To accurately assess the impact of these signs on driver behavior, a before-after study must be implemented on one or more vertical curve locations. Given that such a study must reflect driver reactions to roadway messages, detailed vehicle trajectories must be collected. To capture speed trajectories of vehicles traversing vertical curves, the Minnesota Traffic Observatory developed radar-based, data-collection stations. These stations use automotive radar devices along with custom recording equipment and battery power mounted in weatherized cases to quickly and easily collect vehicle trajectory data for analysis. Through control-vehicle passes and instantaneous radar gun measurements, these stations have been shown to reliably measure the speed and position of vehicles traversing a vertical curve. With the two stations developed, a full field implementation could be developed to collect trajectories for analysis both before and after implementation of a new traffic-control device. For larger-scale implementations of these systems, the methodologies in this report could be used for capturing and post-processing of vehicle trajectories, although additional tools for cleaning and analyzing multiple simultaneous vehicle trajectories would be advised.