341. No person may pass(1) where the driver of a vehicle behind him has already signalled his intention to pass or has already begun to pass;
(2) where the visibility is insufficient to allow entry onto the other part of the roadway in safety; or
(3) on a two-way roadway, where the other part of the roadway is not clear of traffic for a sufficient distance to allow him to pass and return to the right of the roadway in safety.