Schools have started again, and many children navigate busy traffic daily. Road safety remains high on the agenda of municipalities. To reduce the number of traffic casualties, a growing number of Dutch cities are lowering the speed limit on major thoroughfares from 50 to 30 km/h. However, research by the AMS Institute and MIT Senseable City Lab shows that simply putting up speed limit signs does not work. To curb road users’ speed, the road must be redesigned.
Many cities want to reduce the speed limit in built-up areas to 30 km per hour. Amsterdam took the lead in 2023, and cities like Rotterdam and Utrecht are following suit.
Various studies have already demonstrated the effect of such a speed reduction: for instance, a study of traffic fatalities in London showed that reducing speed resulted in a decrease of more than 40% in traffic deaths. Lower speeds not only increase safety but also reduce noise pollution and encourage—or so municipalities hope—walking and cycling.
But how do you ensure that traffic slows down? Large-scale research by the MIT Senseable City Lab and AMS Institute shows that a lower speed limit sign does not cause motorists to drive slower. The solution lies in physically redesigning the street. This offers immediate opportunities for the safety of all road users, but, according to the researchers, it requires a coordinated, nationwide approach.
“When you redesign the street, you immediately get more opportunities for other adjustments that increase safety.”
Titus Venverloo
Lead, MIT Senseable City Lab Amsterdam & Program Developer
By Maud Matthies
Adjusting traffic signs provides minimal improvements
For the study, scientists analyzed millions of car speed measurements and tens of thousands of computer vision street images in Amsterdam and Milan. The conclusion is clear: adjusting the signs alone yields hardly any practical benefit.
In streets where only the speed limit sign was altered to 30 km/h, the average speed was only 2.3 km/h lower than in comparable 50 km/h streets. Using artificial intelligence and computer vision, the researchers mapped which street characteristics effectively influence driving behavior.
What does work: a physical redesign of the street
Since 2023, the Kattenburgerstraat and the Weesperstraat have undergone significant changes. For instance, the Weesperstraat has been given narrower lanes and a wider central reservation, while the Kattenburgerstraat has now, among other things, speed bumps and a wider central reservation.
Moreover, the bus stops on the lane instead of at a recess. And all these measures work. Streets with strong 'spatial confinement', such as narrow lanes, densely packed buildings, and trees, cause drivers to slow down automatically. The physical environment provides the psychological stimulus that driving fast is not safe. The analysis also showed that wide roads with good visibility unconsciously invite motorists to keep hitting 50 km/h.
According to co-author Titus Venverloo (Program Developer at AMS Institute and Researcher at MIT Senseable City Lab in Amsterdam), it is necessary to tackle public space more drastically. Moreover, a physical redesign of the street solves more than just speeding:
"When you redesign the street, you immediately get more opportunities for other adjustments that increase safety," explains Venverloo. "For example, you can create wider bike paths, which provide more space for faster-riding e-bikes."
Due to the rise in e-bikes and other small modes of transport on cycle paths, the speed difference is increasing, leading to risky situations. Narrowing the car lane creates space to widen cycle paths and separate different traffic flows better.
However, physically redesigning streets is a costly and complex undertaking for municipalities. Although there are many local initiatives, overarching coordination is currently lacking. Venverloo emphasizes that cities cannot solve this alone: "While all these solutions are being considered locally, a national approach is missing. If we want this in cities across the Netherlands, but every city does it individually, without a national plan with central government funding, then it will become a very difficult task."
Make better decisions with AI
To assist municipalities, the researchers have developed an AI model. Based on street images, this model predicts how well motorists will adhere to the speed limit at a specific location. This allows cities to identify precisely where interventions, such as visual bottlenecks or additional greenery, will have the greatest effect.
According to Marjan Hagenzieker, Professor of Road Safety at TU Delft, the study is “interesting because it provides empirical substantiation for the idea that a systems approach is needed to promote road safety. The findings align well with other recent research into driving speeds in 30 km/h zones in the Netherlands and emphasize the importance of road design for road safety.”
The message of the study is clear: 30 km/h on paper is not enough. True road safety requires smarter street design, supported by a clear national vision.
Press coverage
The substance of this article has been covered by Dutch and Italian media. You can find the relevant links below. If you are a member of the press and would like to learn more, please feel free to get in touch.
La Repubblica: https://milano.repubblica.it/cronaca/2026/08/24/news/zone_30_milano_ricerca_mit_come_cambiare_le_strade-425543094/
