COBA has been the standard cost benefit appraisal tool for highway schemes in England and Wales for nearly thirty years. However, during the 1980's the appraisal of congested urban area schemes was more often undertaken by applying COBA economic values directly to the results from traffic models. This process was formalised in 1988 with the release of a program called URECA. Both COBA and URECA then operated with fixed trip matrices (FTM), in which it was assumed that a new highway scheme would not affect the traffic volume, only the route choice, or assignment, of traffic. The publication of the 1994 SACTRA report 'Trunk Roads and the Generation of Traffic' ultimately led to the requirement to carry out traffic modelling using a variable trip matrix (VTM) approach. This in turn led to the development of a VTM version of URECA and a method for modifying COBA outputs to deal with VTM. However both COBA and URECA remained unimodal, only being capable of assessing benefits for highway traffic. Also, they calculated benefits on a link by link basis making it difficult to disaggregate costs and benefits for different users, whether by traveller type or origin-destination movement. The Government's White Paper (DETR, 1998) on integrated transport required a wide range of alternative transport options to be considered in meeting the objectives of the New Approach To Appraisal (NATA). Thus the first requirement was for a new method that could appraise highway schemes, public transport schemes and policy options (such as tolling) on the same basis. A second requirement was to identify the full range of 'winners and losers' and the disaggregation of costs and benefits to users of the transport system, the operators and providers. A third requirement was for a method to calculate benefits with either fixed or variable trip matrices. The methodology that meets these requirements is set out in the Guidance on the Methodology for Multi-Modal Studies (GOMMMS, DETR, 2000). This is in accordance with the approach recommended by Sugden (1999). This method has been implemented in the new computer program called TUBA (Transport Users Benefit Appraisal). The key differences from COBA and URECA are that it is multi-modal, its method is matrix-based rather than link-based, and it uses a willingness to pay method rather than social costs and benefits. At the same time the unit of account has been changed from factor costs to market prices. The full version of TUBA was officially released in March 2001, although pre-release versions had been used earlier on the multi-modal studies currently being conducted in England. This paper explains the new method and how it differs from COBA and URECA. The new software is described and possible further developments are discussed. The paper concludes with some feedback from TUBA users.
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