Many streets in Rotterdam go to a maximum 30 km per hour for safety reasons. Will Rotterdam road users comply? Scientist Dr Inge Merkelbach researched this with her team commissioned by the Municipality of Rotterdam. "The majority of Rotterdammers are in favour of the speed reduction. To convince the rest, we came up with solutions, such as making adjustments to the road and clearly communicating the social norm."
Rotterdam has already reduced the speed from 50 to 30 km/h on many roads, such as Walenburgerweg. Just changing the sign from 50 to 30 does not appear to be the solution. More is needed. "Another study shows that the speed on the Walenburgerweg has not yet gone down enough," says Merkelbach, associate professor of behavioural change and social transitions.
Convincing Rotterdammers to drive less fast
The difference between 30km/h and 50km/h seems small, but in practice it is very big. An accident on a 30 km/h road is 90% less likely to be fatal than an accident on a 50 km/h road. Merkelbach: "But many people don't know this. This is the main reason the municipality wants to bring down the speed. On 30-km-per-hour roads, there are also far fewer accidents."
Several solution approaches have been formulated from the research group so that Rotterdammers stick to 30km/h. One example is communicating the social norm. "The thinking is: nobody is going to stick to it and nobody thinks it's important. But our data shows the opposite. Two thirds of Rotterdammers want to stick to the 30km/h. By communicating that, you immediately ensure that people break the rules less. Most would like to be part of the big group and do well. That's in us."
"84% of those surveyed think other Rotterdammers will not stick to 30 km/h"
Inge Merkelbach
Little trust in fellow city dwellers
Trust in other Rotterdammers is a lot less: 84% of those surveyed think others do not take their foot off the accelerator.
"We see this more often. We think we ourselves follow the rules neatly and others don't. This is called attribution bias. If you show bad behaviour yourself it is because of the environment, we think. We see this as an exception. But if someone else does, it belongs to that person. This result was to be expected, but it is extremely strong here at 84%", says Inge Merkelbach.
What does that look like in practice? According to the researcher, you can convince motorists to drive more gently by placing signs along the road with information. "The new standard should be very visible in the streetscape. By putting stripes on the road, roads appear narrower and motorists automatically drive slower. A carving on the road makes you feel like you are driving faster. This makes people drive more slowly. Reminders on the road surface are important. Especially in the beginning to break the automatic behaviour."
We cannot put speed bumps everywhere
Changes to the road surface are probably needed in certain streets to get the speed adjusted to 30 km/h. That will be a job for Rotterdam, where the city centre was built after World War II precisely with the car in mind. Merkelbach: "Unlike Utrecht or Amsterdam, many roads here invite speeding. After all, road features tell us what the right speed is without paying very much attention to the signs. But in Rotterdam, those road features are quite often motorway-like, which makes us drive faster (asphalt, wide roads). We need to work on that with the proposals we have made. In the end, it saves a lot of fatalities on the road."
According to Merkelbach, the best solution remains street modification. "That works even better than all the behavioural insights, but we cannot put speed bumps all over the city. The emergency services are not happy with that either. A combination of physical changes on the road and behavioural insights is needed for that."
- Assistant professor
- More information
The study was conducted by research group BIG'R on behalf of the Municipality of Rotterdam.
The results of the study can be read in the advisory report (Dutch).
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