In a standard appraisal of a road scheme buses should be treated as part of the traffic flow, and the operating cost formulae (described above) are applied, using the appropriate parameter values for PSVs. In a multi-modal study, however, different options may result not only in faster or slower running times for existing bus services, but in the need for more or different levels and patterns of bus service provision. In these cases, the impact of options on the costs of bus service provision have to be considered in more detail.
