Xi’an’s planned restrictions and ban on old vehicles with high emissions were based on level of emission rather than registration time, said officials on Tuesday.

The restrictions were made public in a draft by the city’s environmental and public security departments on Monday. The rules plan to prohibit gasoline and natural gas cars registered before August 2008 from entering the city’s main urban area.

Some car owners and experts said the draft infringed upon consumers’ right.

“The draft’s traffic control standard is vehicles’ level of emission instead of registration time,” said Li Bo, deputy director of Xi’an environmental protection bureau.

The draft, which aims to reduce pollutant emissions and improve air quality, said old vehicles with high emissions will be either restricted or banned in next two years.

The old vehicles with high emissions were gasoline and natural gas cars registered before August 2008 and diesel cars registered before July 2013, it said.

Those two time points are separate when the National III emission standard and National IV emission standard came into effect, Li said.

“Gasoline and natural gas cars with National II emission standard and below as well as diesel cars with National III emission standard and below will be restricted,” he said.

The draft said that old diesel vehicles would be banned from entering the city’s third ring road once the regulation is released. From August 2019, all old cars with high emissions would be forbidden from running inside the third ring road and suburban counties’ main areas. Those cars would be fully prohibited from entering the whole city from August 2020, it said.

Li said the reason why the draft used registration time was to help the public easily check if their private cars meet the requirement.