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DOUBLE WHITE LINES
| Step 2 | For one direction of travel, mark each of the points where desirable minimum visibility distance V is lost, and where it is regained. Each of these pairs of points can now be joined by a continuous white line to create a series of line segments, except where such a segment would be shorter than V / 4, and would be separated from its preceding and succeeding segments by at least the relevant V (note 1(a) below); such short isolated segments should not be marked as continuous unless there is very good justification for retaining them. |
| Step 3 | On the exit from a left hand bend, the continuous line should be extended until the warning line visibility distance W is attained, or the road ceases to curve to the left, whichever results in the shorter line. |
| Step 4 | Gaps shorter than the relevant V (note 1(a)) between continuous line segments should be closed by extending the continuous line. |
| Step 5 | Repeat Steps 2, 3 and 4 for the other direction of travel. |
| Step 6 | On the plan, mark broken lines alongside remaining single continuous lines, on the appropriate side (i.e. on the side for the direction of travel in which a driver has visibility better than V). This will result in the creation of a number of lengths of double white lines. |
| Step 7 | If the gap between two lengths of double white line systems is shorter than half the relevant V value (notes 1(b) and 2 below), the systems should be extended, without a change in pattern, to fill the gap. Normally the systems would meet in the middle of the gap, but the designer should adjust the point of meeting to minimise loss of length from overtaking sections (note 3), or to avoid the release of traffic at an unsuitable point. |
| Step 8 | If this joining of systems results in a length of broken line within the resulting system (i.e. not at one end) that is shorter than the relevant V (note 1(a)), then that length of broken line should be replaced by a continuous line. |
| Step 9 | If the gap between two systems is greater than half the relevant V (note 1(b)), but less than the relevant W (note 4), warning lines should be laid in the gap between the systems. |
| Step 10 | If traffic leaving a length of double white lines is subject to a continuous line that extends beyond the point where the continuous line for traffic in the other direction starts, and it seems that this might cause confusion, the inbound continuous line may be started sooner, at the designer's discretion. |
| NOTES: | |
| 1(a) | In a particular direction, the relevant V value for a gap between two continuous lines is taken to be the same as that used to determine the start of the continuous line after the gap. |
| (b) | When considering the gap between two systems, if the application of note 1(a) results in a different V in each direction, the greater value should be used. |
| 2 | V / 2 is used here in preference to V to avoid excessive lengths of unnecessary continuous line. Overtaking lengths less than V that might arise are closed later, at Step 8. |
| 3 | When adjusting the meeting point of systems, the designer should take account of the availability of other (perhaps safer) overtaking opportunities in the vicinity. |
| 4 | The relevant W value at any point is taken to be that for the speed corresponding to the relevant V value at that point, defined under 1(a) and 1(b) above. |
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