No vehicle to stop near an uncontrolled crossing

The driver of a vehicle shall not cause the vehicle or any part thereof to stop within 45', or any lesser distance as shall be indicated by a line drawn in accordance with paragraph 3 of the Schedule to these Regulations, of an uncontrolled crossing on the side of the road on which such line is placed or if the road is a one-way street on either side of the road: Provided that a vehicle shall not be prevented from stopping by this regulation– (i) to comply with the provisions of regulation 4; (ii) if the driver is prevented from proceeding by circumstances beyond his control; (iii) if it is necessary for the driver to stop in order to prevent an accident; or 20 (iv) for so long as may be necessary to enable the vehicle, if it cannot be used for such purpose without stopping on that part of the road, to be used for fire brigade, ambulance or police purposes or for defence purposes, or in connection with any building or demolition operations, the removal of any obstruction to traffic, the maintenance or reconstruction of that part of the road or the laying, erection, alteration or repair in or near to that part of the road of any main, pipe or apparatus for the supply of water or electricity, or of any telegraph or telephone wires, cables, posts or supports.