Representing the fleet of light-duty vehicles (LDV) in economy-wide models is important for projections of transportation demand, energy use, and resulting emissions. This paper presents a methodology for incorporating private transportation details into an economy-wide model and (using an example of the MIT Economic Projection and Policy Analysis (EPPA) model) a description of calibrating the model to the data. The authors provide results both for light-duty internal combustion engine (ICE) vehicles and electric vehicles (EV). For the EV fleet, both plug-in hybrid vehicles (PHEV) and battery electric vehicles (BEV) are considered. First, they find that the global LDV stock increased by about 45% in ten years, from 735 million in 2005 to 1.1 billion in 2015; over the same period in China (the fastest growing market), LDV stock increased from 20 million to 140 million. Second, they assess relative costs of ICE, PHEV and BEV vehicles. Based on consumer prices and battery pack/vehicle components cost estimates in the U.S., they find that compared to ICEs, PHEVs are about 30-60% more expensive and BEVs are about 40-90% more expensive. Finally, they project that global LDV stock will grow from 1.1 billion vehicles in 2015 to 1.8 billion in 2050, while global EV stock will grow from approximately one million to 500 million over the same period. The study’s methodology can be applied in other energy-economic models to test the sensitivity of the results to different input assumptions and specifications.