Zebra crossings installed close to junctions can reduce the vehicular capacity of the junction in two situations: when they are upstream of the junction (on the approach side) and by 'blocking back' from a downstream crossing (on the exit side). this report quantifies these effects. The interaction between an upstream zebra crossing and a junction entry is discussed with reference to the theory of two sequential serving units, and a method of calculating the reduction in the junction entry capacity due to the presence of the crossing is derived. Information is given to enable the capacity of the individual units (crossing and entry) to be found and a method is then outlined for the application of these capacities to evaluate the effect of a given crossing location on the crossing/entry combination. The problem of 'blocking back' from the crossing on the exit side of the junction is also considered and numerical results given which enable this effect to be evaluated. A practical procedure for evaluating these effects is given and an example of a zebra crossing situated on the approach to a roundabout entry is used to illustrate the method. (Author/publisher)
Abstract