Abstract
The only really satisfactory solution of the problem of crossing the road is separation, preferably in space, by over and under passes. This is not always either possible or desirable for technical, financial or aesthetic reasons. When separation in space is not possible, separation in time is the only answer, by momentarily transforming the carriageway into a pedestrian way at specific points. The safest way is generally accepted to be by light controlled crossings, but these cannot be placed at all points where pedestrian flows warrant a crossing.