Drivers' comprehension of traffic information on graphical route information panels

The concept of using signs to display graphical traffic information is now becoming increasingly popular. The main objective of this study was to design and undertake laboratory research to examine whether the content of traffic information displayed on graphical route information panel (GRIP) could be readily understood. Six kinds of GRIP signs that composed of three changeable information contents (road color only, road color with journey time, and road color with traffic speed) and two different road network types (triangle and tetragon) were proposed and tested in the experiment. Results showed that GRIP with road color only had the greatest optimum route choice percentage and the fastest response time compared to the other contents. On the contrary, GRIP with traffic speed had the slowest response time and the least optimum route choice percentage. Participants took less response time and greater optimum route choice percentage for triangle road network than for tetragon road network. Further, changeable information content interacted with road network type on response time and optimum route choice percentage. The road network type had little effect on response time and optimum route choice percentage under road color only, whereas under road color with journey time and road color with traffic speed, response times increased and optimum route choice percentage decreased significantly as road network complexity increased. Considering drivers' comprehension and response, using road color only to present traffic condition on GRIP could be an applicable solution. Road color with traffic speed presented on GRIP was not recommended. Road color with journey time can be used for a simple road network. However, it was not suggested for a complex road network. The findings of this study could assist in displaying suitable traffic information on GRIP and in improving efficient driving for motorists.