Road signs which depict children’s book illustrations temporarily reduce speed on urban roads, according to new research.

The study from SWOV, the Institute for Road Safety Research in the Netherlands, evaluated the speed of drivers on roads with signs created by the late illustrator and writer of books for toddlers, Dick Bruna.

The Dick Bruna signs were originally designed to evoke feelings of caution and care in drivers to make them drive slower.

As part of the study researchers asked participants to look at photos from a driver’s perspective on roads with and without a Dick Bruna sign. They had to report how fast they expected others would drive and how fast they themselves would drive.

Speeds on photos with a Dick Bruna sign were reported as being approximately 4 km/h lower than on the same photos without and speeds were not significantly lower when a neutral sign such as an advertisement was visible.

In a second study speeds were measured on a road during seven consecutive weeks with Dick Bruma signs placed during weeks 3–5.

Researchers found the signs appeared to reduce speed slightly, but the effect was only visible during the first week after placements of the signs.