In order to solve the problem of freight vehicles passing through heavily polluted cities, Hebei Province gives priority to "4+2" cities, which cities do this mean?

In order to solve the problem of freight vehicles passing through heavily polluted cities, Hebei Province gives priority to the planning and construction of roads around the city in "4+2" cities (Handan, Xingtai, Shijiazhuang, Baoding, Dingzhou and Xinji). Guide foreign vehicles to use vehicles that meet emission standards to enter the province for transit and bypass at the far end. Strengthen the route control of transit freight vehicles and guide heavy transport vehicles to give priority to the passage of heavy vehicle owners. Relying on the transportation overload control station, do a good job in the control of inferior loose coal, and do a good job in the verification of road transport certificates for loose coal transport vehicles.