Like any other maneuver, changing lanes has certain dangers for drivers to avoid. As the Ontario.ca website notes, drivers in Ontario are not allowed to change lanes within 30 metres of a crosswalk to avoid taking their attention away from anyone who might be crossing the road. In addition, drivers should not pass another vehicle over the centre line between two directions of traffic within 30 metres of a bridge, viaduct, or tunnel. Changing lanes while approaching the crest of a hill is also inadvisable as the driver might be unable to see any oncoming traffic.