Abstract
The importance from the Traffic Engineers' point of view of a fuller under standing of human abilities and their limitations is discussed. As an example of the sort of basic data which are useful the results of investigation into the time allowances required by pedestrians when crossing a traffic stream are given. Some observations on the use by pedestrians of subways and bridges are reported and information is given to enable such safe facilities to be planned with some confidence that they will be fully used. (1) Choosing a safe gap in a traffic stream. (2) Choosing where to cross the road.