Logo UHasselt




Congestion warning dynamic traffic signs: an ideal design

Logo UHasselt Universiteit Hasselt - Knowledge in action


We queue innumerable hours on an annual basis. When possible, the Flemish traffic centre alerts drivers for congestion using dynamic traffic signs. Currently, several variants of congestion warning messages are used without having underpinned insights in the effectiveness of the available variants. The Flemish traffic centre asked IMOB to compare them and to identify the most efficient one.

In this study, IMOB focuses on the tactical use of the dynamic signs. Does the driver adjust his driving behaviour after reading the warning message? If so, how? Does he slow down or does he wait until the last moment to brake? The strategic use of information panels, that suggests drivers to take an alternative route, was not investigated in this study.

40 subjects participated in the driving simulator study. IMOB-researchers developed seven situations to compare the impact of the presence or non-presence of congestion warning on dynamic signs. Traffic jams were announced on several ways. The researchers integrated pictographs and/or text, varied the distances between the digital traffic sign and the congestion tail, displayed different amounts of information and used two types of traffic signs (gantry/ cantilever). A gantry hangs over the roadway entirely, while a cantilever is placed next to the roadway, only hanging over slightly.

The researchers linked the data of the driving simulator study with the looking and driving behaviour of the test subjects. They did a few important observations and converted them into recommendations for the Flemish traffic centre.

Back to overview >