CARLSBAD, Calif. — Nine new miles of carpool lane will make life easier for commuters who regularly drive back and forth through northern San Diego County.

Caltrans and SANDAG crews completed the new lane on southbound Interstate 5 Wednesday. Running between Palomar Airport Road and Lomas Santa Fe Drive, the stretch of freeway takes drivers from Carlsbad through Encinitas and then into Solana Beach. Crews completed a northbound carpool lane for the same stretch of freeway last month.

Drivers who have at least one passenger, or a car with a valid HOV access sticker because it is an electric or otherwise “clean air” vehicle, can take advantage of the extra lane.

“These new lanes aim to improve traffic flow, reduce greenhouse gas emissions on the highway, provide more travel options, and reduce vehicle miles traveled,” the transportation agencies wrote in a joint news release. “Sound walls were also constructed as part of the project to abate future noise levels.”

The lanes are part of the broader Build North Coast Corridor project. Local and federal agencies started collaborating on a variety of transportation improvements in 2017, ranging from bike and pedestrian trails to railroad track work and the new HOV lanes.

By the time crews complete the project in 2023, drivers will have access to four additional miles of carpool lanes from Palomar Airport Road in Carlsbad to state Route 78, making 13 new miles on I-5 overall.

Senate Bill 1, an act signed by state lawmakers in 2017, provided $54 billion for similar improvements across California over the course of a decade. Of the roughly $5 billion from SB1 that’s split between state and local agencies annually, $195 million went toward the new carpool lanes. The Build NCC project also relies on funding from TransNet, the state’s voter-approved, half-cent sales tax for transportation projects.