Paragraph 3

It shall be possible to raise and lower the barriers. When lowered, the barrier shall be as nearly horizontal as possible, be as nearly as possible at right angles to the centre line of the carriageway and shall extend across the left hand side of the road. The tip of each barrier shall extend to a point within 800 mm of the centre of the carriageway and no closer than 150 mm and a clear exit of at least 3 metres of carriageway width shall be left to the right hand edge of the carriageway.