After passing through a customs plaza, it enters Sarnia and travels parallel to and north of Exmouth Street through the city. Although Highway 402 passes through Sarnia, it is not intended to operate as a commuter highway; at Highway 40 and westward all ramps leading to the westbound lanes of the freeway were originally signed as "Bridge To U.S.A." without reference to Highway 402, though these have been replaced in the early 2000s with signs saying "402 West Bridge To U.S.A.".