Modern traffic control devices to improve safety at rural intersections.

PDFTech ReportFHWA/TX-12/0-6462-1Project 0-6462Traffic control devicesRural highwaysIntersectionsHighway safetyTexasUnited States. Federal Highway AdministrationFitzpatrick, KayChrysler, SusanSunkari, SrinivasaCooper, JoelPark, Byung-JungHiggins, LauraTexas Transportation InstituteTexas. Dept. of Transportation. Research and Technology Implementation OfficeUnited States. Federal Highway AdministrationUS Transportation Collection"Engineers with the Texas Department of Transportation (TxDOT) frequently make changes to traffic control devices(TCDs) to improve intersection safety. To use available funds judiciously, engineers make incremental changes inorder to select the least costly yet effective improvements. The goal of this project was to obtain a betterunderstanding of modern TCD capabilities. Researchers conducted the following tasks: literature review, crash dataexamination, TxDOT district survey, laboratory survey, field study, and development of principles for selectingTCDs. Adding flashing lights to signs, either through beacons or embedded light-emitting diodes (LEDs), serves twopurposes: to attract attention and to convey a message. The findings of this research demonstrate that while the lightsdo improve detection distance, legibility distance of the message suffers at night due to the glare of the lights.Cautious engineering judgment should be used when adding lights to any word message sign beyond a Stop signbecause the legibility distance for the words will be shorter than when lights are not present. For Stop signs, theunique color and shape of these traffic control devices prompts drivers\ue2\u20ac\u2122 responses to them long before the word \ue2\u20ac\u153stop\ue2\u20ac?is actually read. The driving study found no difference in sign detection at night between those with an overheadflashing beacon and those where the ground-mounted sign has embedded LEDs. The detection distances observed forthe signs with lights in this study were extremely long, over 2000 ft in most cases. The other general observationregarding the magnitude of the results is that for all of the Stop signs, both lit and unlit, the detection distance for signrecognition was always greater than stopping sight distance. So the existing static Stop signs are sufficiently visiblefor an alert driver under clear weather. The research project found that there appears to be a benefit to detection fromdimming the LED brightness at night. The LED sign set on the high brightness setting was detected furthest duringthe day, while the lower setting was detected best at night. The research concluded with guidance principles toconsider when selecting countermeasures for rural stop-controlled intersections.