Be careful out there. The road is about to shift in Montecito.

Starting Saturday night, southbound traffic on Highway 101 will shift toward the median and be divided by safety barriers from Olive Mill Road to Posilipo Lane, which is near the Rosewood Miramar Beach hotel, according to Caltrans.

The southbound onramp at Olive Mill Road and the southbound offramp at San Ysidro Road will close for construction that same night.

The changes are part of the massive Highway 101 project to add a third lane between Carpinteria and Santa Barbara.

The northbound “crossover” ended in late June, and crews opened the updated onramps at San Ysidro Road and Hermosillo Road, according to the Santa Barbara County Association of Governments.

Having southbound divided lanes will allow crews to build new lanes while keeping two lanes of traffic open in each direction of Highway 101.

According to Caltrans, the southbound onramp at Olive Mill Road will be closed for nine months for construction. Drivers can use a detour along North Jameson Lane to access the southbound onramp at Sheffield Drive.

Crews have been working for years on adding a third, carpool lane between Santa Barbara and Carpinteria. Phases have been constructed south to north.

Construction in the Montecito and Santa Barbara South segments is anticipated through 2026.

More project updates are available at SBROADS.com.

The Highway 101 project is a partnership of Caltrans, the Santa Barbara County Association of Governments, Santa Barbara County, and the cities of Carpinteria and Santa Barbara.

The cost for construction of the five segments is approximately $700 million.