Heavy Duty Vehicles (HDV) produce significant vehicular emissions, which are expected to increase in Ireland due to economic growth and the associated increase in freight transport. Ireland has adopted the European Low Emission Mobility Strategy and the national target of achieving 20% energy efficiency by 2020. From these targets comes the imminent need to address the issue of vehicle emissions from the Irish HDV fleet. The main objective of the MAP-HDV† project was to investigate emission-mitigating measures to reduce emissions from the Irish HDV sector. In MAP-HDV project the Vehicle Energy Consumption Calculation Tool (VECTO) tool has been effectively used and for the first time to analyse Irish HDV. This paper shows the results of investigating the impact of speed, acceleration, loading factor and alternative fuels on fuel consumption and CO2 emissions using the VECTO tool.