Uber announced Tuesday that it will levy a surcharge for its ride-hailing passengers in London. The goal: to get 20,000 drivers to go all-electric by the end of 2021, on the way to make every car using its ride-hailing app an electric vehicle in the smog- and congestion-prone city by 2025.

The surcharge, which is part of the company’s clean-air strategy announced in 2017, will go into effect in early 2019. It’s potentially as much an environmental image move as it is a response to ever-tightening rules governing the vehicle types that can pass through central London.

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Beginning early next year, Uber will charge riders about 19 cents (15 pence) extra per mile. That money will go directly into a piggy bank for the support of drivers looking to upgrade to an electric vehicle.

Uber app

Uber app

Based on the average London trip, that will amount to an extra 58 cents per trip. And through that surcharge Uber hopes to raise $260 million (200 million pounds) over several years.

Uber is offering a significant amount of upgrade money. Every driver will be eligible for assistance in moving to an EV, but the level of assistance will be based on how many miles they’ve driven on the app. It’s anticipating that will add up to about $3,900 (3,000 pounds) for two years of driving—40 hours a week—or $5,800 (4,500 pounds) for three years.

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The program complements Uber’s own diesel-scrappage scheme that aims to get 1,000 pre-Euro 4 diesel models—older, dirtier ones—off London streets and highways.

So far in the U.S., Uber’s strategies to electrify have been a bit different. Through a pilot program it calls EV Champions, it’s paying drivers up to $20 per week for driving electric—and giving riders a feel-good alert. Whether it will incentivize electric vehicles more or less effectively than the London program remains to be seen.