It is sometimes claimed that transport infrastructure projects have network effects, which are not taken into account in the appraisal of these projects. This paper reviews the concept of network effects, relates this to transport appraisal practice, and links to the concept of 'total economic...

In 1998, the UK Government published the results of its Roads Review. For each of the 68 schemes considered, an Appraisal Summary Table was produced, giving the scheme performance against the Government's five objectives--environment, safety, economy, accessibility and integration. This paper...

Twenty-one sources of error and bias in the appraisal of transport projects are identified. These relate to objectives, definitions, data, models and evaluation conventions. Objectives may be unclear, incompletely specified or inconsistent with appraisal criteria. Definitions of study areas and...