Arizona is ending a program that allowed drivers of certain hybrid cars to use the carpool lane even if just one person was in the vehicle.

The Energy Efficient Plate Program lets plug-in hybrid cars, and some older non-plug-in hybrids, use the high-occupancy vehicle lane if they had the “energy-efficient” license plates that display a blue sky with white clouds.

Doug Nick, a spokesman for the Arizona Department of Transportation, said the federal law that authorized the energy efficiency program expired Sept. 30 and the state won’t issue any more such plates starting March 2.

“We have no choice but to follow the law and when that expired, we joined all the other states,” Nick said.

Current plate-holders will continue to have access to the HOV lane, but the plate loses its validity if the car is sold, transferred or traded, according to ADOT

Before the March deadline, hybrid car owners with an eligible plate can transfer it to another eligible vehicle.

The program started in 2007 and had a cap of 10,000 license plates, Nick said. Every few years, the program opened to more participants. More than 5,600 vehicles have the “energy-efficient” plate.

Drivers of alternative energy vehicles with plates that look similar but say “alternative fuel” are not affected. Those vehicles are fully electric, or have another non-gasoline fuel source and include cars like the Tesla Model 3, S and X, Nissan Leaf, Chevrolet Bolt EV, and Audi E-Tron.