Visibility and Spacing of Lane Control Signals for Freeway Traffic Management (1498-1)

Glance legibility studies conducted at the TTI Proving Grounds examined the legibility of three commercially available LCS with respect to symbol, signal type, subject gender, and subject age. Also, the effect of ambient light conditions was also explored. Symbols on all three signals resulted in median glance legibility distances of 304.8 meters (1000 feet) or greater, whereas the 85th percentile glance legibility distance was 213.4 meters (700 feet) or greater. Of the various factors examined, only the age of the subject significantly influenced legibility distances. In general, drivers 65 years and older had to be 91.5 to 198.1 meters (300 to 650 feet) closer to the signals to correctly identify the symbols being displayed than drivers aged 16 to 44 years.|The report also contains the results of a meeting of TxDOT operations personnel involved in freeway LCS design and operaion. Panel members identified a number of specific problems and concerns regarding LCS design and operation. Panel members identified a number of specific problems and concerns regarding LCS on freeways, and brainstormed about potential solutions and countermeasures to address these concerns.