Electric and hybrids now account for about one-fifth of new car sales on average in the six biggest Chinese cities, according to data from the China Passenger Car Association.

Consumers in developed cities on China’s east coast have embraced EVs faster than their inland neighbors thanks to local government policies, like easier access to license plates. But Cui warned with rising traffic jams and higher overall EV penetration, that favorable treatment may not last.

Shanghai, for example, may start restricting license plate issuance for some small EVs such as SAIC-GM-Wuling Automobile Co.’s Hongguang Mini, according to local media reports. Cars that are shorter than 4.6 meters and sell for under 100,000 yuan ($15,500) won’t be given preferential treatment like free plates, Caijing said, citing sources it didn’t identify.

However whether Shanghai adjusts its policy or not, it’s unlikely to impact overall EV sales in China longer-term, Cui said.