Vlakveld and teammates studied how to slow drivers using road signs. They focused on “road signs displaying children’s book illustrations. These signs display illustrations which were created by the late illustrator and writer of books for toddlers, Dick Bruna. . . . participants watched photos from the driver’s perspective. 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 approximately 4 km/h lower than on the same photos without a Dick Bruna sign and speeds were not significantly lower when a neutral sign such as an advertisement was visible. In the second study speeds were measured during seven consecutive weeks on five experimental roads and five comparison roads. On the experimental roads, during the week 3–5 a Dick Bruna sign was placed. Controlled for developments in speed on the comparison roads in the same period, mean speed was marginally significant lower.” The “Dick Bruna” signs show human cartoon characters with large round heads and bodies.
Willem Vlakveld, Charles Goldenbeld, and Jolieke De Groot. 2022. “Road Signs Depicting Childrens’s Book Illustrations Temporarily Reduce Speed on Urban Roads.” Transportation Research Part F: Traffic Psychology and Behaviour, vol. 87, pp. 236-248, https://doi.org/10.1016/j.trf.2022.04.005