The future of personal transportation will be shaped by population growth, urban congestion, environmental pollution, global warming, and the depletion of natural resources. Through evolutionary changes, future personal transportation will be comprised of a greater diversity of powerplants, fuels, and modes than currently exists. Reciprocating internal combustion engines, and in particular the spark-ignition homogeneous-charge variety, are likely to continue being the dominant powerplant in personal transportation if their real contribution to pollution can be controlled.Key emissions control issues are as follows. For evaporative emissions, lengthy vehicle parking at high temperatures (resting losses) is a previously unaccounted for source of hydrocarbons, which will require better evaporative emissions control systems, better thermal management of the fuel system, and low volatility fuels. Sources of exhaust emissions, particularly carbon monoxide, that may be underestimated in current emissions inventories are those from cold and transient vehicle operation, such as severe accelerations. Results show that for vehicles equipped with homogeneous-charge internal combustion engines operating with closed-loop air-fuel ratio control systems, and using three-way catalysts, improved control of emissions during cold and transient operation will require improved thermal and air-fuel ratio management.