| 85 percentile speed (mph) |
Desirable minimum visibility distance V (m) |
Warning line visibility distance W (m) |
|---|---|---|
| Up to 30 | 75 | 115 |
| 31 to 40 | 95 | 160 |
| 41 to 50 | 120 | 195 |
| 51 to 60 | 150 | 240 |
| Over 60 | 175 | 275 |
4.21 The minor road should be marked with at leastthe minimum number of marks shown in table 4-3. On narrow two-way minor roads where the Give Way or Stop marking is extended over the whole width(see para 3.3), a warning line is not provided.
4.22 If the minor road is a one-way street, a warning line on the major road will normally be needed only if the direction of flow is towards the major road. The principal purpose of the marking is to warn drivers of the risk of unseen vehicles emerging.
4.23 A warning line approaching a refuge, central reservation etc. should be inclined for its full length(see table 4-3 for the minimum number of marks), terminating in a position offset 300 mm from the edge of the refuge (see figure4-4). This may be reduced when the speed limit is 40 mph or less and there is limited width between the island and the near side kerb, but should preferably not be less than 150 mm. Kerb faces will not normally exceed 75mm, because of the risk of loss of control if struck by a vehicle. Where unusually high kerbs are used, the 300 mm clearance should always be provided. When the length of taper required to comply with table 14-1 needs more marks than the minimum specified in table 4-3, the number of marks should be increased sufficiently to ensure that the entire taper length uses the warning module. Guidance on the use of hatched markings for additional emphasis is given in paras 4.49 to 4.51 and further advice on the treatment of refuges in section 14.
4.24 On dual carriageway roads, or single carriageway roads with two or more lanes in one direction, warning lines should be used in place of lane lines on the immediate approach to signal controlled junctions or roundabouts. Where additional lanes are introduced on the immediate approach to a roundabout it might not be possible to provide the minimum number of marks. In such cases as many marks as possible should be used without reducing any lane width below 2 m at the start of the taper (see para 8.3). The detailed arrangements for marking roundabouts and signal controlled junctions are described in sections 8 and 9 respectively.
4.25 The number of marks recommended in table 4-3 is the minimum on each approach, although this is not always possible on minor roads. The number of marks should be extended wherever justified by road or traffic conditions; the marking can with benefit be extended to start at the location of the accompanying warning sign. Figure 4-5 indicates
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