In the past it has been common practice, on two-way carriageways of approximately 30 ft. width, to lay down intermittent white lines dividing the carriageway into three traffic lanes. The central lane was intended to be used by overtaking traffic proceeding in either direction. In our view this layout is unsound as the middle lane encourages overtaking under unsuitable conditions and may thus lead to head-on collisions. We therefore recommend that the marking of three traffic lanes on two-way carriageways should be discontinued, and that existing markings of this type should be replaced by a single centre line separating the opposing streams of traffic. Two-way carriageways should be divided into either two or four lanes as appropriate to their width. In making this recommendation we give effect to views expressed in the Report of the Select Committee of the House of Lords on the Prevention of Road Accidents, published in 1939.
We consider it essential that the marking of intermittent centre lines separating opposing streams of traffic on two-way roads should be uniform, and recommend that it should consist of a 9 ft. mark with 9 ft. gap. Intermittent lines separating streams of traffic proceeding in the same direction, i.e. lane marking on dual carriageways and the side lines on four-lane two-way carriageways, should consist of a 3 ft. mark and 15 ft. gap.
Intermittent longitudinal lines should always be stopped 1oo ft. short of any continuous central white line laid down in accordance with the recommendations made in paragraphs 147 to 149.
White lines defining main carriageway boundary
151. Intermittent white lines, mark 3 ft., gap 3 ft., are useful for indicating the boundary of the main carriageway at entrances to side roads, lay-bys, roadside dumps, etc., and where an accelerating or decelerating lane is provided at a junction. These lines are particularly helpful at night and in fog.
Reflecting studs
152. The use of self-cleansing reflector studs of approved pattern set in longitudinal white lines has proved of great benefit to traffic. We recommend that their use for this purpose should be formally authorised by the Minister. On intermittent lines the studs should be set in the centre of alternate gaps, i.e. at 36 ft. centres. On continuous lines a spacing of 12 ft. is recommended. Studs of this type should not be used on the carriageway in any other circumstances, nor should they be laid down on roads where the standard of street lighting is such that headlamps are not used. Reflecting studs are of little value in these latter conditions, since they depend for their effect on the reflection of the headlamp beam. The projection of the studs above the road surface should be as small as possible consistent with optical efficiency.
Colour of “white” lines
153. The 1933 Provisional Regulations authorised the use of white or yellow colour for lines and other traffic signs on the carriageway. We do not consider that yellow has any advantages over white for carriageway markings and we think it desirable that there should be uniformity in practice. We therefore recommend that white only should be authorised for carriageway markings. It is our intention in this connection that “white” should be interpreted as permitting the use of light coloured materials such as stainless steel.
We have considered various suggestions about the use of other colours in special circumstances, e.g. black on concrete surfaces, a red line across the entrance to a carriageway to which entry is prohibited, and a green line across the near half of the carriageway to give advance warning of a standard roadside sign, but do not recommend their adoption.
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