One of the busiest roadways in Southern California will look a little different in December once a major improvement project is completed.

The I-405 Improvement Project is expected to be completed on Dec. 1, and with it, two new regular lanes and new Express Lanes will open in Orange County.

The project, which was overseen by the Orange County Transportation Authority, has been in the works since 2018.

The project was born out of the notion that population, employment and housing would continue to bloom along the 16-mile segment of which the project spans, and OCTA expects that these improvements will have a major impact on traffic and travel times.

Each side of the freeway between the 605 Freeway in Seal Beach and Euclid Street in Fountain Valley will have a new regular lane beginning Dec. 1. Additionally, Express Lanes will be opened between the 605 and Highway 73 in Orange County.

Those lanes are tolled for solo drivers, free for vehicles with two occupants during non-peak hours, and always toll-free for vehicles with three or more occupants, motorcyclists and those with veteran and disabled license plates. Vehicles will need to have a FasTrak transponder and a valid account with any toll agency in California to enter these lanes and take advantage of the service.

Toll fees will vary depending on the day of week and time of day, with an average cost expected to be around $3, OCTA says. The most expensive time to drive in the lanes will likely be Friday afternoons.

While the transportation agency hopes to have the project fully off the ground by December, testing is needed on the new Express Lanes.

Beginning as early as this Wednesday night, the northbound carpool lane at Highway 73 will be closed for testing. Carpool lanes in both directions between Highway 22 and the 605 Freeway will also be closed as early as Nov. 1. Both those closures are expected to begin around 11 p.m.

Officials say the plan is to have the new and improved 405 Freeway up and running by Dec. 1, but stress that the timeline is subject to change.

The $2.16 billion improvement project is financed through a combination of local, state and federal funds, with the majority coming through funding brought forth from the passage of Measure M — Orange County’s half-cent sales tax for transportation.

The Express Lanes were funded separately through a federal loan, which will be paid back by the toll fees collected. Once paid off entirely, toll fees will be directed toward freeway improvement projects, OCTA says.