Information as a Source of Distraction

015835972015Final Report; 2011-07-15 to 2013-09-30PDFTech ReportFHWA-HRT-15-027DTFH61-08-C-00006DistractionDriversDriving simulatorsEye movementsGuide signsLegibilityRecommendationsSpacingVariable message signsHighwaysOperations and Traffic ManagementSafety and Human FactorsI73: Traffic ControlI83: Accidents and the Human FactorDistractionChangeable message signCMSSupplemental guide signSpecific service signSign frequencySign contentUnited StatesUnited States. Federal Highway AdministrationInman, Vaughan W.Bertola, Mary AnnePhilips, Brian H.LeidosUnited States. Federal Highway Administration. Office of Research, Development, and TechnologyTurner-Fairbank Highway Research CenterFederal Highway AdministrationThe overall goal of the Information as a Source of Distraction project was to further the scientific basis for decisions about the types of information that can be displayed within the right-of-way without adversely affecting drivers\u2019 attention to their primary task\u2014safe driving. There were two focus areas: electronic changeable message highway signs (CMS) and guide signs. Six studies were conducted. The first study examined the perceived similarity between messages on a full-color, full-matrix, light-emitting diode CMS display with 0.79-inch (20-mm) pixel pitch and the same messages on a liquid crystal display. The purpose of that study was to derive requirements for laboratory and driving simulation studies of CMS messaging. The second study examined the legibility distance for text message on the CMS display used in the first study. It was determined that, assuming 20/40 vision, legibility distance could be estimated using a letter height of 1 inch (2.54 cm) per 20 ft (6.1 m) of viewing distance. In the third study, drivers read the CMS display as they approached it on a closed course that required them to simultaneously navigate a curved path. The effects of CMS message properties such as flashing, phasing, abbreviations, and use of symbols versus text were examined. The fourth and fifth studies simulated overhead CMS messages on a freeway on which there was a CMS every 0.5 mi (0.8 km). By displaying highly salient images (faces on brightly colored backgrounds) that changed every 3 s, an attempt was made to distract drivers. Drivers did not look at the salient images more often or longer than they looked at travel-time messages. When headways were short, the salient signs had a 0.2 probability of receiving a brief look. None of the signs caused drivers to miss safety-critical messages encountered later in the drive. None of the signs caused drivers to fail to detect a roadway hazard (spilled logs). The final study examined the effects of the frequency and spacing of guide signs on navigation performance and eye-glance behavior. That study supported retaining current Manual of Uniform Traffic Control Devices for Streets and Highways standards and recommendations for guide signs and suggested further research on the design of specific service logo signs