In this study, potential vehicle manufacturing costs, lifecycle costs, infrastructure support costs, and emission-related costs are compared for three potential zero-emission vehicle (ZEV) technology development and deployment scenarios. These scenarios include production of mid-sized battery electric vehicles direct-hydrogen fuel cell vehicles, and direct methanol fuel cell vehicles from 2003 to 2026, and operation of the vehicles in California's South Coast Air Basin (SCAB) from 2003 to 2043. The study focuses on potential manufacturing cost reductions for electric motors, motor controllers, battery systems, hydrogen storage tanks, and fuel cell systems, due to the combined forces of production scale economies and technological progress. Vehicle manufacturing and lifecycle costs are calculated by integrating vehicle component cost functions with a detailed vehicle performance and cost spreadsheet model. Fleet-level costs for vehicle operation, infrastructure development, and criteria pollutant and greenhouse gas emissions are calculated using a MATLAB/Simulink model developed by the author. In this regional-scale, fleet-level model, fuzzy set theory is used to characterize uncertainty in key input variables, and to propagate uncertainty through the calculation of vehicle, infrastructure, and emissions costs. Findings are that estimated ZEV purchase prices drop steadily with production volume and technological progress, but that even in future, high-volume production the estimated purchase prices for all three ZEV types remain above those of comparable conventional vehicles. However, lifecycle costs for ZEVs in some cases become competitive with those of comparable conventional vehicles, especially for direct-hydrogen fuel cell vehicles. When infrastructure and emission-related costs are considered for vehicles used in the SCAB, total lifecycle costs for direct-hydrogen fuel cell vehicles are found to be below those of even low-emission gasoline vehicles by 2026, under central case assumptions. Meanwhile, total lifecycle costs for battery EVs and direct-methanol fuel cell vehicles are found to be between those of conventional and low-emission gasoline vehicles, again in the year 2026 central case. In general, the overall level of uncertainty in the calculation of total scenario net present values is considerable, and this level of uncertainty prevents the unequivocal determination of a least-cost ZEV technology pathway for the SCAB.