(20)Non-exhaust emissions consist of particles emitted by tyres and brakes of vehicles. Emissions from tyres are estimated to be the largest source of microplastics released into the environment. As shown in the impact assessment accompanying the proposal for this Regulation, it is expected that by 2050 non-exhaust emissions will constitute up to 90 % of all particles emitted by road transport, because exhaust particles will diminish due to vehicle electrification. Those non-exhaust emissions should therefore be measured and limited. The Commission should encourage the work of UN WP.29 in order to achieve its objectives in a timely manner, reflecting a high level of ambition based on solid scientific and technical grounds, and to define abrasion limits on the basis of state-of-the-art methods. In the event that uniform provisions on tyre abrasion limits have not been adopted by UN WP.29 by 1 July 2026 for C 1 class tyres, 1 April 2028 for C 2 class tyres or 1 April 2030 for C 3 class tyres, the Commission should adopt a delegated act aimed at reaching the Union’s objective to reduce microplastics released into the environment by 30 % by 2030 and based on state-of-the-art abrasion limits. Specific characteristics of vehicles with traction batteries, including plug-in hybrids and battery electric vehicles should be evaluated during the preparation of that delegated act.