California plug-in car drivers with white or green carpool stickers can no longer use carpool lanes starting Tuesday.

The state passed a new program last March that invalidates both the white stickers for electric cars and the green stickers for plug-in hybrids with the start of 2019.

For many of those drivers, the state provided a way to extend carpool access, but drivers have to reapply for new red stickers that don't expire until New Year's Day 2022.

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Only cars sold since the start of 2017, however, qualify—along with older cars that have never had California carpool stickers, such as those brought in from out of state.

California purple carpool sticker

California purple carpool sticker

New plug-in cars bought in the new year will qualify for new purple carpool stickers which expire Jan. 1, 2023. By then, California will update the program and may issue new colors with more distant expiration dates.

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Carpool-lane access in the congested state has been a big motivation for many plug-in and electric-car buyers. So many, in fact, were buying electric cars for access to the carpool lanes that those lanes in some places were becoming as congested as regular traffic lanes.

As a remedy, the state decided to set a rolling format for its carpool stickers, so instead of new electric-car buyers getting permanent access to carpool lanes, buyers will get access for four years at a time. The object is to get those buyers to purchase new electric cars at the end of four years to get more electric cars on the road.

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The ones they trade in, with expired stickers, will go to used-car buyers, presumably at lower prices than if their stickers were still valid.

We just hope the new program doesn't create a run on used plug-in models from other states, just as the structure of legal plug-in car mandates is beginning to require automakers to actually sell plug-ins outside of California.

 Update 2: An earlier version of this story incorrectly said the new red and purple stickers expire concurrently. The error has been corrected and GCR editors regret the error.