LOS ANGELES (AP) — Charging drivers for access to express lanes on one of Los Angeles’ busiest freeways appears to have only partially resolved commuter travel woes: Transportation officials say so many people are using the new toll lanes that the paid route is slowing down too.

Traffic in toll lanes rose almost 20 percent even as the per-mile toll crept toward the maximum, the Los Angeles Times reports.

Metropolitan Transportation Authority officials are now trying to reduce traffic on the 110 Freeway by creating a “carpool only” restriction during the heaviest rush hour periods. Some researchers say a more viable, long-term solution is to keep raising prices.

Tolls on the 110 in Los Angeles County range from 25 cents to $1.40 a mile, with a maximum price of $15.40.

“The fact that the speeds are getting low suggests prices aren’t high enough,” Clifford Winston, a Brookings Institute economist, told the Times. “There’s no such thing as a price ceiling. If tolls went up to $10 per mile, I’m sure it would have an effect.”

Some drivers said they wouldn’t be reluctant to pay more.

“My time is very precious,” said Val Wright, 40, an independent consultant with three daughters. “I want to make sure I’m hope as quickly as I can be.”