Visibility and Spacing of Lane Control Signals for Freeway Traffic Management

摘要

Glance legibility studies conducted at the TTI Proving Grounds examined thelegibility 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.