The economic appraisal of transport schemes continues to evolve; the latest development being the consideration of wider economic benefits (WEBs). To analyse the WEBs of transport (including its impact on agglomeration and labour productivity) it is necessary to estimate the impact of transporton employment location. It is standard practice when modelling commuting destination choice to (doubly-) constrain the number of commuting trips travelling to a given area to meet (a suitably scaled fraction of) local employment totals. In late 2007, UK Department for Transport (DfT) commissioned MVA Consultancy and David Simmonds Consultancy (DSC) to document the methodology applied to wider economic benefits (WEB) calculation using the London Transportation Studies (LTS) model, with particular emphasis on the application of the singly-constrained commuting distribution model to the estimation of employment impacts. This paper reports the findings of that study and begins with a step-by-step methodological outline of the approach, including general background on the LTS model and the key assumptions made in the analysis and modelling. The outputs taken from the transport model and their application in the WEB estimation are discussed. The robustness of the approach and the transferability of the procedure to other model platforms and geographical locations are considered. The application of singly-constrained transport models (SCTM) to estimation of employment impacts in LTS proved to be both effective and efficient. Direct transfer of the method to other models is possible, though the practicalities would depend strongly on the structure of that model. That said, cut-down approaches can be devised to permit the rapid application of SCTM techniques to many model types (even those with fixed matrices), albeit at the expense of internal consistency. Methods were found to improve the quality of the results in conjunction with tests carried out using a full Land Use TransportInteraction (LUTI) model. From the point of view of comparison with a LUTI approach, while SCTM journey to work trip-end changes may be taken as indicators of employment change, they may not be responding to the most appropriate transport cost changes. For example, retail employment may be a function of goods delivery costs. Also, SCTMs do not take account explicitlyof any of the feedback or linkage which may arise. The study recommended that, in order to compare the relative merits of SCTM with a LUTI method for estimating employment impacts, both methods should be used on one or more test cases. for the covering abstract see ITRD E145999
Samenvatting