How do children estimate the speed of a vehicle in a 3D environment?

Children in the lower grades of elementary school aged 6 to 9, although they rarely participate in traffic independently, represent a vulnerable population. Among other things, children have problems estimating the speed (and in some situations also the direction) of the vehicle. For the purposes of this experiment, participants were simultaneously shown two videos of 3D vehicles on the screen. Test vehicle speeds are 30 km/h, 50 km/h and 80 km/h. The participants had the task of estimating which vehicle was moving faster or which vehicles were moving at the same speed. 38 respondents participated in the experiment. The results showed that there are differences between the estimated vehicle speeds.