Substitution of bus for car travel in urban Britain: an economic evaluation of bus and car exhaust emission and other costs

Car exhaust emissions cause serious air pollution problems in many regions and, at a global level, contribute to climate change. Car use is also an im portant factor in other problems including traffic congestion, road acciden ts, noise pollution, community severance, and loss of countryside from road building. Forecasts of further increases in car ownership and use have pro mpted calls for policy-makers to encourage car users to switch to other for ms of transport, particularly the bus. The effects of substituting bus for car travel in urban areas are simulated by specifying a spreadsheet model i ncorporating two types of car (petrol and diesel engine) and three types of bus (mini-, midi- and large bus). Six types of exhaust emission are consid ered for each vehicle type for the years 1992, 1995 and 1999: carbon monoxi de, volatile organic compounds, nitrogen oxides, sulphur dioxide, (small) p articulate matter and carbon dioxide. The paper provides a synthesis of mon etary estimates of these exhaust emission and other costs. The other costs considered are traffic congestion, fuel consumption, noise pollution, road accidents and road damage. The exhaust emission monetary cost estimates, ma inly from the United States and the United Kingdom, are discussed within th e context of a sensitivity analysis which allows for changes in parameters such as load factors, emission factors and the individual exhaust emission cost estimates. The simulation results show that substitution of bus for ca r travel generally decreases the overall costs, particularly the costs of c ongestion, but increases exhaust emission costs if bus load factors are ins ufficiently high. In order to reduce exhaust emission costs from car to bus transfer at given load factors, the most effective policy option is to enc ourage the reduction of particulate emissions from bus engines. In terms of the overall costs, increasing bus load factors by relatively modest amount s can lead to substantial reductions in these overall costs. These results should be regarded as illustrative rather than definitive, given the uncert ainties in a number of parameter estimates and the need for further researc h in areas not covered by the paper. (C) 1999 Elsevier Science Ltd. All rig hts reserved.