Evaluation of Comprehension and Legibility of International and Domestic Nonstandard Symbol Signs

This paper documents a research project that evaluated proposed new traffic signs to ensure that the signs were effective when human factors requirements were taken into consideration. The following sign messages were selected for symbol development and evaluation: combination horizontal alignment–advisory speed, congestion ahead, cross-street preferential lane warning, do not enter, do not pass, electric-vehicle charging station, fallen rocks, flagger ahead, low-shoulder warning, maximum width, no left turn ahead, railroad crossing on leg of roundabout, road narrows, survey crew, trolley crossing, uneven lanes, and winery. The team conducted 96 surveys to determine driver comprehension and legibility for each alternative sign design. The surveys were administered to the general driving public at the Turner–Fairbank Highway Research Center in McLean, Virginia. On the basis of driver input and the results of the comprehension and legibility testing, the research team provided recommendations on symbols that should be included in the next edition of the Manual on Uniform Traffic Control Devices.