Excess or wasteful commuting in a selection of British cities

This research considers the application of an urban zonal travel optimisation model to the actual commuting patterns between residences and workplaces in a selection of large British cities in 1981 and 1991. The model produces an estimate of the average commuting distance required if individuals could exchange residences and workplaces to minimise distance travelled. The proportion of the actual commuting distance above the optimum is defined as excess or wasteful commuting. The existing literature has pointed to some reservations about this methodology. This research fuels this debate and for the first time the importance of inward commuting into the designated city is highlighted. The results indicate that it is the changing form of urban areas, which is exerting the strongest influence on the increasing length of work journeys. It is important to distinguish between intra-urban changes (where trip lengths have increased only slightly) and those outside the city boundaries. Within some cities, recent changes show that workplaces and residences have, on average, moved closer implying greater potential efficiency. Yet, comparing actual travel distance change with change in the theoretically optimum travel distance, it is clear that excess commuting has increased by reasonably significant fractions. On the other hand, when a wider view of the daily urban system is taken, it becomes apparent that the dominant role is being played by the wider decentralisation of employees. This results in increases in average travel distances but these can be shown to be less than the increases in the theoretically optimum average distances which result if travel distances are minimised. The clear effect is for excess commuting to decline in almost all cities over the decade, and sometimes by significantly large amounts. (C) 1998 Elsevier Science Ltd. All rights reserved.