D5.11GUIDE ISLANDS
D5.11.1 Guide islands should be provided where a single three-lane carriageway road is reduced to one or two lanes; see Plans SC6 and SC8. Minimum taper lengths for guide islands are given in Table A1.3 (Appendix 1). Lengths of guide islands excluding tapers are given in Table 5.6 below.
| Standard works | Relaxations | |
|---|---|---|
| Roads for which national speed limit applies | 200 m | 100 m |
| Roads with a permanent speed limit of 50 mph or less | 100 m | 50 m |
D5.11.2 When guide islands are used in conjunction with positive traffic control (priority signs, "STOP/GO" signs, and traffic signal control) the taper lengths should be as given in Table 5.3.
D5.12USE OF CHICANES
D5.12.1 For short lengths of shuttle working, i.e. 50 m or less, chicanes can be used to reduce traffic speeds, where necessary, to less than 10 mph. At least one chicane in each direction is required, of the minimum size to allow a large vehicle to pass through slowly, and traffic must first be brought to a halt by positive traffic control and then released in small batches by careful use of “STOP/GO” signs or manually controlled portable traffic signals. The principle is shown in Plan CH1. Where it is impracticable to provide a chicane in one direction, for example, because of the presence of a junction, an alternative traffic management arrangement should be used in that direction to ensure that traffic speeds are reduced to less than 10 mph.
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