Researchers at IMOB, the Institute for Mobility at UHasselt University, want to understand how road design can cause drivers to slow down. It is generally known that introducing a 30 km/h zone by simply putting up a sign is not enough; you also have to redesign the road. Otherwise, it won’t work.

Scientists also want to find out whether a measure that makes Belgian drivers slow down would have the same effect in Croatia or Sweden. The joint study on road design and driving behavior is part of the European TwinSAFE project, in which UHasselt collaborates with the University of Zagreb and Lund University.

They are now looking for test subjects willing to experience various traffic situations in a driving simulator. Candidates must be at least 18 years old and hold a valid category B driver’s license. Individuals who suffer from epilepsy, migraines, motion sickness, or a concussion should refrain from participating.

Cultural differences?

TwinSAFE aims to strengthen road safety research in Europe by sharing knowledge and research experience among the three universities. This aligns with a broader European ambition: the EU intends to reduce road fatalities and serious injuries by 50 percent by 2030.

All three countries are testing the same scenarios, adapted to local conditions. This allows the test results to be compared side by side. “Ultimately, we want to be able to determine whether a particular measure works everywhere, or whether there are, in fact, cultural differences,” says Ali Pirdavani of UHasselt.

“We use a driving simulator for safety. We compare driving behavior in a given situation – first without a specific measure in place, and then with it. If the intervention proves effective, we then test the scenario on the actual road.” All test subjects in the simulator experience the exact same traffic situation. This allows for a valid comparison of the results.

Similar scientific research

In 2025, UHasselt published similar scientific research with concrete results. Furthermore, field studies from the Netherlands, the United Kingdom, and the United States confirm that a speed limit sign alone is generally insufficient.

For example, researchers found that a row of trees along the road had no significant effect, that drivers tended to start slowing down when encountering transverse road markings, and that these markings – when combined with a physical narrowing of the road – achieved the best balance between speed and controlled driving behavior.

On a winding road or chicane, the researchers observed the strongest braking effect, but also abrupt braking or evasive maneuvers at times, and renewed acceleration. Another notable conclusion was that an intervention at the village boundary is not sufficient to change driving behavior throughout the entire village.

Other European countries

Recent Dutch research by SWOV from May 2026 into the effect of lowering the speed limit from 50 to 30 km/h revealed that the average actual speed driven was 35.3 km/h; without any redesign of the road, the reduction in speed was only 2 km/h, while with a redesign, it was approximately 5.5 km/h.

British researchers investigated the effect of interventions at village entrances but found that speed control within the village itself remained limited without additional measures.

The French government agency Cerema determined that road shifts physically compel drivers to adjust their speed. The US FHWA (Federal HighWay Administration) found that speed display signs, raised platforms, and median islands were particularly effective. Purely visual road narrowings or painted warnings generally had little effect.

Guidelines

Flanders, however, already has guidelines for designing a transition to a lower speed – specifically, a lateral shift in the road alignment combined with a central median – to signal to drivers that they are entering a different type of traffic environment.

The key lesson from various countries is that a village entrance should not merely be recognizable as such; the entire road design must match the desired speed. A wide, straight, and open stretch of asphalt will always invite drivers to speed, even if the official speed limit is 30 km/h.