The justification for a crossing facility is assessed by reference to a Department for Transport Assessment Framework (Local Transport Note 1/95) which includes such factors as average waiting times for pedestrians to cross, estimated vehicle delay if a crossing is installed, accident history, vehicle and pedestrian volumes and composition, site characteristics and installation/maintenance costs. The pre- 1995 criteria of a PV squared formula (no.of pedestrians x no.of vehicles squared to exceed a value of 100 million) is still useful in terms of prioritising locations for consideration, but does not form part of the assessment framework.
There are situations, such as few gaps in traffic and long pedestrian waiting times or speeds, that would indicate the location is unsuitable for a zebra crossing and a signal controlled crossing would be more appropriate. At the other end of the scale, a site with low traffic flows and little pedestrian delay might not require a formal crossing at all, and a pedestrian refuge might be more appropriate, if one can be accommodated.
There is already considerable flexibility in interpreting the results of the Assessment Framework but the primary determinant is still likely to be the availability of funds and relation to other priorities. For instance, if a facility forms part of a larger pedestrian route, then it may be possible to seek funding from a relevant associated budget (e.g. school travel plans). Equally, if the proposal is likely to reduce casualties at a location then it may qualify as a Local Safety Scheme.