SACRAMENTO, Calif. (KTXL) — The California Highway Patrol and Caltrans have partnered together to launch a “maximum enforcement period” on a 12-mile stretch of State Highway 99 to help reduce carpool lane violators between Sacramento and Elk Grove, according to Caltrans.

According to a news release from Caltrans, this campaign will begin on Sept. 19 and continue through Oct. 15 during weekday commute hours from 6 a.m. to 10 a.m., and then from 3 p.m. to 7 p.m.

Motorcycles, mass transit, and vehicles with two or more occupants are allowed to use the High-Occupancy Lanes during those commuting times. Certain plug-in hybrids, alternative fuel, and electric or other clean-air vehicles are also allowed to use the HOV lanes, despite the number of occupants in the vehicle.

The news release said that studies indicate that HOV lanes are effective in promoting carpooling while also improving the flow of traffic. HOV lanes also are an “incentive for motorists to purchase zero-emission vehicles.”

Caltrans said that recent traffic counts reported that 47% of traffic violations on northbound Highway 99 and 35% of traffic violations on southbound Highway 99, were carpool lane violations.

According to Caltrans, when drivers illegally use the HOV lanes during commuter hours it can increase congestion and slow traffic “below speeds accepted by the Federal Highway Administration.” The FHWA requires that traffic speeds in HOV lanes must be 45 mph or greater than 90% of the time during peak commute times.

If vehicles do not reach those speeds, the FHWA can designate that the HOV lanes as degraded which could then lead Caltrans to modify the eligibility requirements of the current HOV lanes.

A representative from Caltrans told FOX40 that this maximum enforcement period is more of a deterrent so single occupancy drivers will be more aware and not drive in HOV lanes during commuter hours.