Beijing is moving to phase out gas-powered taxis as part of an effort to tackle its crippling smog levels.
Smog in the city is on the decline but it still worst among Chinese cities.
To help clear the air, 70,000 gas taxis in the city will be replaced with electric vehicles as part of a government plan.
In the short-term, however, electric taxis may make the problem worse, because China is heavily dependent on coal.
Tsinghua University found that charging electric vehicles emits two to five times as much particulate matter as gasoline-fueled cars.
Electric vehicles are cleaner in the long run, as China adds more renewable power as part of its effort to cut its 2015 carbon emissions by 18 percent by 2020.
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