The project of creating a low-emission zone in the Great Paris area (Métropole du Grand Paris) has started in 2015 with an experimental "restricted circulation zone" (zone à circulation restreinte) in Paris. It was followed by studies and public consultation, before being implemented on 1 July 2019. Very polluting heavy and light-duty vehicles can only circulate between 20h and 8h. Vehicles are divided in 6 categories Crit'Air, according to their emissions. The current plan is to progressively restrict access to the Great Paris area to non or less polluting vehicles. The overall goal is to reach 100% of clean vehicles circulating in the area by 2030. Individuals whose vehicles do not fit the criteria to circulate in the area can apply for the Conversion Premium (Prime à la conversion) (see separate entry).