The state traffic laws clearly provide that one is not required to stop if they are traveling in the inverse or opposite direction of a school bus on a highway separated by a median strip or a central reservation where the traffic is moving in one direction OR when they are on a completely separate trunk from the vehicles traveling in the opposite direction.
The same is also applied when one is not traveling in the opposite direction of a school bus on a freeway containing four lanes or more.
For more information about traffic laws please see the following link:
