This study modelled the Passenger (PC) fleet and other categories of road transport in Ireland from 2015 to 2035 to assess the impact of current and potential greenhouse gas mitigation policies on CO2 emissions. Scenarios included the shift of purchasing towards diesel PCs over gasoline PCs. Scrappage rates were also calculated and applied to the fleet to predict future sales of PCs. Seven future policy scenarios were examined using different penetrations of PC sales for different vehicle technologies under current and alternative bio-fuel obligations. Tank to Wheel (T2W) tailpipe and Well to Wheel (W2W) CO2 emissions, and energy demand were modelled using COPERT 4v11.3 and a recently published W2W CO2 emissions model. A percentage reduction of conventional diesel and petrol vehicles, in different scenarios compared to a baseline scenario in the W2W model was applied to estimate the likely changes in T2W emissions at the tailpipe up to 2035. The results revealed that the biofuel policy scenario was insufficient in achieving a significant reduction of CO2 emissions. However, without a fixed reduction target for CO2 from the road transport sector, the success of policy scenarios in the long run is difficult to compare. The current Electric vehicle (EV) policy in Ireland is required to be implemented to reduce CO2 emissions by a significant level. Results also show that a similar achievement of CO2 emission reduction could be possible by using alternative vehicle technologies with higher abatement cost. However, as EV based policies have not been successful so far, Ireland may need to search for alternative pathways. (C) 2016 Elsevier Ltd. All rights reserved.