We have developed a Truck Choice Model (TCM) and used the model outputs to create vehicle technology market scenarios as inputs to our Transportation Transition Model. The model formalism is reasonable well developed, but the choice factors contain significant uncertainties (especially non-monetary factors). Phase two would advance the choice modeling work with a new truck choice survey of fleets, and possibly a 2nd workshop, followed by an updated analysis of TCO and non-market costs of different truck types and revision and major publication of our existing truck choice report.The model will be updated and expanded as described in project 1 (Transportation Models Updates and Expansion). The first TCM paper described the model and gave sales shares for the various technologies for 3 scenarios (BAU, ZEV, ZEV + Biofuels). These scenarios were produced with a single set of inputs (vehicle costs, fuel costs, payback period, vehicle VMT, etc.).This project will include more scenarios, determine which inputs affect the sales shares most, and do a sensitivity analysis on those inputs.