This Directive requires Member States to ensure that contracting authorities and contracting entities take into account lifetime energy and environmental impacts, including energy consumption and emissions of CO2 and of certain pollutants, when procuring certain road transport vehicles with the objectives of promoting and stimulating the market for clean and energy-efficient vehicles and of improving the contribution of the transport sector to the environment, climate and energy policies of the Union. Clean Vehicles Directive 2019 requires a minimum percentage of clean vehicles in the aggregate public procurement across a Member State. A Member State has to meet at least half of the procurement target for clean buses in each period through the procurement of zero-emission buses.