A woman suspected of driving under the influence and two passengers are dead following a crash on Highway 12 in San Joaquin County Sunday afternoon, the California Highway Patrol said.

The crash site sits along a bustling corridor for traffic heading onto the highway or deeper into Napa, with a gas station to the north and a park-and-ride to the south. The offramp, lined with scattered trees and plants, was shut down until noon as investigators worked to determine how fast the sedan was traveling before impact.