Motorists heading south on Interstate 5 near the San Ysidro Land Port of Entry will experience significant traffic delays when a $2.7 million construction project begins next week.

The work will take place in two phases over roughly three weeks and is aimed at improving safety, security and traffic flow at the busy border crossing, according to the California Highway Patrol.

The first phase begins at 9 p.m. Tuesday and runs through 5 a.m. Jan. 9, and includes the closure of the Camino de la Plaza on-ramp and the six western-most lanes of southbound I-5.

Southbound traffic on I-5 and Interstate 805 will merge into fewer lanes as vehicles approach the border, while the Camino de la Plaza off-ramp and access to Tijuana, Mexico, through the El Chaparral crossing will remain open.

Crews will remove speed humps near the southbound inspection booths and replace temporary concrete barriers with permanent dividers, the CHP said.

The second phase of construction will begin immediately after the first phase’s completion and continue through 5 a.m. Jan. 23, CHP officials said.

Phase two includes a continuous closure of the eastern-most inside lane on southbound I-5 within the center median at the San Ysidro Land Port of Entry. Access to Tijuana through the El Chaparral crossing will remain open, while the Camino de la Plaza off-ramp will also remain open.

CHP officials urged drivers to plan ahead and expect delays, recommending the Otay Mesa Land Port of Entry or public transit when possible.

Traffic enforcement will be increased during construction.

The project is being carried out by the General Services Administration, which manages federal property.