The legibility of LED traffic guide signs in urban tunnels

The legibility of traffic signs in urban tunnels is of great importance on traffic safety. To improve legibility of traffic signs, this paper attempts to assess the siting and layout of LED traffic guide signs by simulation and field tests. First, the test scenarios were built in DIALUX software, where drivers' legibility distance were recorded with regard to twenty-four signs with different colors, font sizes, and contrast ratios. Then, to confirm the results from simulation, twenty LED traffic guide signs with different layouts were designed. Different layouts were set up with varying sign sizes, height-width ratios, thickness of stroke and light emitting forms. By setting up those traffic guide signs, field tests are conducted on Tongji University campus, South Tibet road tunnel and Shangzhong tunnel in Shanghai. Finally, according to the experimental results, the optimal design for urban tunnels with speed of 60km/h is recommended regarding legibility distance.