When a school bus stops on a multi-lane highway (three lanes in the same direction) to let students alight, how should motor vehicles in adjacent and outer lanes respond?

1. All three lanes may maintain maximum highway speed without slowing
2. Vehicles in the lane directly adjacent to the school bus must stop; vehicles in the outer lane may pass at a speed not exceeding 20 km/h
3. Only heavy commercial trucks must stop; small passenger cars may pass freely
4. All vehicles in all directions across the entire roadway must turn off their engines