Post Implementation Scheme Evaluation: Were the COBA Accurate?



Post Implementation Scheme Evaluation: Were the COBA Accurate?

Authors

KNIGHT P and POWELL G, Oscar Faber and WHITTAKER B, Highways Agency, UK

Description

A major aim of the current Trunk Road programme is to aid economic recovery by providing cost effective reductions in journey times, congestion and accidents on the road network. The concept of cost-benefit analysis for new road construction is central to

Abstract

A major aim of the current Trunk Road programme is to aid economic recovery by providing cost effective reductions in journey times, congestion and accidents on the road network. The concept of cost-benefit analysis for new road construction is central to the appraisal process. This is embodied in the COBA program which calculates the savings in time, operating costs and accidents which are forecast to occur following scheme opening. By comparing these costs with the capital and other costs, the schemes overall economic value can be assessed. A further advantage of COBA is that by adopting a standardised approach to all schemes, the Highways Agency is able to compare the relative scale of cost and benefits for different schemes and hence determine priorities for expenditure.

In recent years there has been increased interest in determining whether the traffic levels predicted for new or improved roads do actually materialise. Studies carried out in 1989 by the National Audit Office identified apparent wide variations between forecast and outturn traffic flow levels on new schemes. Although these variations could have arisen for many reasons, this work increased concern about the accuracy of the forecast economic benefits for new Trunk Road schemes.

Thus, in 1993, the Department of Transport (DOT) commissioned a consultancy study, the aim of which was to measure the level of economic benefits that actually accrue from recently completed Trunk Road programme schemes.

Publisher

Association for European Transport