Assessing Message Display Formats of Portable Variable Message Signs

A study on the message display formats of portable variable message signs (VMSs) is presented. Through a series of laboratory driving simulation experiments, the influences of the interaction between display format and number of message lines and driving lanes were investigated. In the simulation, digitally created VMS stimuli were inserted into a driver's-view driving video, and the video was projected onto a screen in front of a stationary vehicle. Eighteen subjects from three age groups with balanced gender participated in the experiments. Each subject, sitting in the driver's seat of the vehicle, was required to make proper responses signaling comprehension of the VMS stimuli. Subjects’ responses and accuracy were recorded in a database. On the basis of the statistical analysis of the collected data, it was found that discretely displayed messages took less response time than sequentially displayed messages. Singleline messages were better than multiple-line messages. Motorists could better view portable VMSs when they were driving in the outer lane. It was also found that older drivers exhibited slower response and less accuracy than younger drivers; women drivers exhibited slower response but higher accuracy than men drivers.