The Impact of Design Factors on Drivers’ and Non-Drivers’ Comprehension of Variable Message Signs

This study examines differences in comprehension between drivers and non-drivers when interpreting variable message signs (VMSs) combining three elements-a pictogram, an arrow, and a city name-to indicate temporary traffic events (e.g., "congestion before Lyon"). A total of 101 participants (51 non-drivers) were shown VMS displays reporting an event associated with one of four cities and were asked to identify the event's location (before or after the city). The experiment employed a mixed factorial design. Two between-subject factors were included: Driving License (present vs. absent) and Route Listing (present vs. absent). Four within-subject factors were manipulated: Complementary Message (present vs. absent), Landmark Order (bottom-up vs. top-down), Event Location (before vs. after), and Arrow Function (explicit vs. generic). The dependent variable was the accuracy of location identification. The results showed that, for drivers, the most effective combination was bottom-up order with an explicit arrow, followed by bottom-up with a generic arrow, and then top-down with an explicit arrow. For non-drivers, no significant differences were found between these combinations. However, comprehension decreased across both groups when the message used a top-down order and a generic arrow. Overall, the data suggest that the G1c template from the 1968 Convention is not effective for either group. Prior driving experience seems to favor one specific design, the bottom-up order with explicit arrow, while non-drivers perceive all functionally viable options-including that one-as equally valid.