Design of Experiment Approach to Study the Display of Variable Message Signs

摘要

This report describes a study on the design and display factors of variable message signs (VMSs). The two-phase study was conducted through a series of blocked-factorial experiments. Computer generated VMS images, merged with a driver's view driving video were projected onto a screen in front of the test vehicle. Subjects in the drivers' seat were required to make proper responses signaling their comprehension of the VMS stimuli. Eighteen subjects balanced by age and gender participated the experiments. Phase I investigated the effects of discretely displayed VMSs' font size, font color, subjects' age, gender, and their interactions. It found that font color, drivers' age, and gender significantly affected response time. Green and 5 x 7 dot matrix font were the best font color and font size respectively. Older drivers responded the fastest among the three age groups but with the lowest accuracy. No significant correlations were found between subjects' response time and accuracy. Response times of different subjects were significantly different, but the effects of font color and size were consistent among different subjects. Adopting specific recommendations based on the phase I findings, phase II studied the influences of display format, number of message lines, weather, driving lane, and their interactions. It found that discretely displayed messages took less response time than sequentially displayed ones. Single-line messages were better than multiple-line ones. Motorists could better view VMSs in sunny days, and better view VMSs when driving in the outer lane. Older drivers exhibited slower response and less accuracy than younger drivers; females exhibited slower response but higher accuracy than males.