This paper draws on recent experiences of using the London Transport Studies (LTS) model as an input to highway scheme appraisal, and attempts to provide guidelines of value to practitioners. It describes the appropriate roles of LTS in relation to: (1) its function in a hierarchical modelling structure; (2) its potential use in scheme appraisal; and (3) alternative methods for obtaining forecasts for scheme appraisal. As a strategic transport model, LTS can provide a consistent set of forecasts for input to local assignment models, reflecting various factors, but it has two limitations. Its two main functions in traffic scheme appraisal are to provide: (1) a future base reference, against which to assess specific schemes; and (2) forecasts of any differences in future year matrices between a scheme's inclusion and omission. The paper presents eleven guidelines for the use of LTS and 13 general guidelines for using strategic models in scheme appraisal. For example, strategic models are appropriate for: (1) understanding schemes' wider travel choice effects beyond reassignment; (2) guiding decisions on the local area assignment model's extent; and (3) providing appropriate trip growth factors.
Abstract