Estimating the crash reduction and vehicle dynamics effects of flashing LED stop signs : final report.

PDFTech Report2014-02CTS Project # 2011003(C) 89261 (WO) 195Stop signsFlashing traffic signalsDriver performanceMinnesota. Dept. of Transportation. Research Services & LibraryDavis, Gary A.Hourdos, JohnXiong, HuiUniversity of Minnesota. Dept. of Civil EngineeringMinnesota. Dept. of Transportation. Research Services & LibraryUS Transportation CollectionA flashing LED stop sign is essentially a normal octagonal stop sign with light emitted diodes (LED) on thestop sign\ue2\u20ac\u2122s corners. A hierarchical Bayes observational before/after study found an estimated reduction ofabout 41.5% in right-angle crashes, but with 95% confidence this reduction could be anywhere between 0%and 70.8%. In a field study, portable video equipment was used to record vehicle approaches at anintersection before and after installation of flashing LED stop signs. After installing the flashing stop signs,there was no change in the relative proportion of clear stops to clear non-stops when minor approachdrivers did not face opposing traffic, but the relative proportion of clear stops increased for drivers who didencounter opposing traffic. Random samples of 60 minor approach vehicles were selected before and afterinstallation of flashing LED stop signs and speeds for these vehicles when about 500 feet from theintersection, and average deceleration rates over the final 500 feet, were estimated using trajectory-basedmethods. Average approach speeds tended to be highest in June, somewhat lower in July, and lower yet inSeptember and November, with September and November having roughly equal average speeds. Theaverage deceleration rates showed a similar pattern