4.29 Diagram 1010 is used instead of diagram 1009 at lay-bys and at acceleration and deceleration splays, and also for emphasising lane drops. Details of the various prescribed uses are set out in table 4-5. The marking may be supplemented with uni-directional reflecting road studs, at the spacing shown in table 4-5. Green reflectors should be used at lane drops, along acceleration and deceleration lanes and at lay-bys.
4.30 Further guidance on the use of diagram 1010 can be found in:
section 10 for grade separated junctions,
section 17 for bus lanes,
section 18 for tram markings, and
4.31 Diagram 1012.1 is intended for general use to delineate the edge of carriageway, particularly on unlit classified roads and those not having clearly defined raised kerbs. It should also normally be used on all-purpose roads with hard shoulders or hardstrips, on motorways, unless profiled edge lines are used (see paras 4.39 to 4.48) and to delineate footways at level crossings (see para 19.9).
4.32 Trials have shown that edge markings have merit as a safety measure despite their efficiency sometimes being impaired by dirt because of their location near the edge of the carriageway. They can also help to protect verges on narrow rural roads.
4.33 The marking should be laid with a gap of approximately 225 mm to the near side edge of the carriageway. The continuous line should not be carried across the mouths of side roads, acceleration or deceleration splays, gaps in the central reservation or lay-bys, where lines to diagrams 1009 or 1010 should be used.
4.34 Where the carriageway is less than 5.5 m in width, the centre line should be omitted (seepara4.6) but edge lines, where used, continued. Where edge lines are not already in use, their introduction over the length where the centre line is interrupted will help draw attention to the hazard.
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