SAN DIEGO -- The new express lanes of Interstate 15 through Carmel Mountain Ranch will debut in mid to late September, along with a movable barrier aimed at easing commute congestion, it was announced Monday.

The project, which has been several years in the making and has already included several areas of realignment of the busy freeway, will give drivers four new lanes, said Edward Cartagena of Caltrans.

The movable barrier, similar to one on the San Diego-Coronado Bay Bridge, will give rush-hour commuters access to three of the four new lanes -- southbound in the morning and northbound in the afternoon, Cartagena said.

"The Interstate 15 express lanes are a freeway within a freeway," said Pedro Orso-Delgado, director of the Caltrans local district office. "The movable barrier in the median can be adapted to suit the traffic demands of the corridor. What we are doing with the makeover of Interstate 15 is creating options for the commuters of San Diego."

To enter the new express lanes when they open, drivers will need to have two or more people in their vehicle, be a FasTrak member or ride a motorcycle.