Effectively addressing concerns about air pollution (especially health impacts of small-particle air pollution), climate change, and oil supply insecurity will probably require radical changes in automotive engine/fuel technologies in directions that offer both the potential for achieving near-zero emissions of air pollutants and greenhouse gases and a diversification of the transport fuel system away from its present exclusive dependence on petroleum.The basis for comparing alternative automotive engine/fuel options in evolving toward these goals in the present analysis is the "societal lifecycle cost" of transportation, including the vehicle first cost (assuming large-scale mass production), fuel costs (assuming a fully developed fuel infrastructure), externality costs for oil supply security, and damage costs for emissions of air pollutants and greenhouse gases calculated over the full fuel cycle.Several engine/fuel options are considered-including current gasoline internal combustion engines and a variety of advanced lightweight vehicles: internal combustion engine vehicles fueled with gasoline or hydrogen; internal combustion engine/hybrid electric vehicles fueled with gasoline, compressed natural gas, Diesel, Fischer-Tropsch liquids or hydrogen; and fuel cell vehicles fueled with gasoline, methanol or hydrogen (from natural gas, coal or wind power). To account for large uncertainties inherent in the analysis (for example in environmental damage costs, in oil supply security costs and in projected mass-produced costs of future vehicles), lifecycle costs are estimated for a range of possible future conditions.Under base-case conditions, several advanced options have roughly comparable lifecycle costs that are lower than for today's conventional gasoline internal combustion engine cars, when environmental and oil supply insecurity externalities are counted-including advanced gasoline internal combustion engine cars, internal combustion engine/hybrid electric cars fueled with gasoline, Diesel, Fischer-Tropsch liquids or compressed natural gas, and hydrogen fuel cell cars.The hydrogen fuel cell car stands out as having the lowest externality costs of any option and, when mass produced and with high valuations of externalities, the least projected lifecycle cost. Particular attention is given to strategies that would enhance the prospects that the hydrogen fuel cell car would eventually become the Car of the Future, while pursuing innovations relating to options based on internal combustion engines that would both assist a transition to hydrogen fuel cell cars and provide significant reductions of externality costs in the near term. (C) 2002 Elsevier Ltd. All rights reserved.