A truck bypass is a roadway that provides physical separation of trucks from passenger vehicles at a freeway interchange in order to eliminate weaving between passenger cars traveling at higher speeds and trucks traveling at lower speeds. Typically a truck bypass exits the main freeway some distance before the interchange it is intended to bypass; trucks are usually required to use the bypass, while passenger cars may choose between the bypass and the main traffic lanes. A truck bypass may take the form of a dedicated roadway (as in the Newhall Pass Interchange) or a collector/distributor road (as in the El Toro Y). The bypass allows vehicles traveling on it to exit the interchange in the same possible directions as the main line of traffic, and then merges with the respective freeway at some point past the interchange.
Truck bypass should not be confused with truck lane; a truck lane is a lane dedicated for trucks on steep inclines that is not physically separated from the main highway.
A notable example of a truck bypass is at the Newhall Pass Interchange in Los Angeles, where trucks traveling on Interstate 5 are separated from passenger cars onto a dedicated roadway – the original U.S. Route 99 over which I-5 was built – located east of the freeway.