Michael Manville, chair and professor of urban planning at UCLA Luskin, spoke to the Los Angeles Times about new rules that are kicking solo drivers of clean-air vehicles out of California’s carpool lanes, raising questions about how commute times and traffic will be affected.

The carpool lane perk was used to promote the adoption of clean and zero-emission vehicles. As of Aug. 14, more than half a million motorists statewide had an active decal on their vehicle to access the lanes.

That privilege ended Oct. 1, and experts say it will take time to see how clean-air vehicle drivers might adapt.

“Will they just throw up their hands and get in traffic with the rest of us in the three [other] lanes, or will they actually do something else, because they really do value not being in traffic?” Manville asked.

He added that, on an already gridlocked freeway during peak drive times, commuters might not even notice one more car that merges in.