guard rail or suitable planting. If this is not possible, segregation should be effected by a physical island of sufficient width to accommodate the peak number of pedestrians.
8.37 Segregated left turn lanes may encourage higher speeds; any desirable speed reduction measures should be applied before entry to the lane and not within it. Where the proportion of large goods vehicles is high, it should be ensured that the lane width is sufficient to accommodate the swept paths of larger vehicles, especially where physical segregation is provided. Where few such vehicles are expected, the lane may be reduced to 3.5 m in width, or exceptionally to an absolute minimum of 3.3 m. Where road markings to diagram 1041.1 or 1042.1 are used to create the lane segregation, the overall width of the marking should normally be at least 1 m. Where reflecting road studs are used, these must be red (see para 6.9).
8.38 When segregation is achieved using road markings alone, no special allowance needs to be made for broken-down vehicles, as other traffic will not be prevented from passing. Where physical segregation is introduced, the design should not prevent vehicles from making a left turn at the roundabout in the normal way by using the non- segregated part of the approach.
YELLOW BOX MARKINGS
8.39 Direction 35 prohibits the use of yellow box markings (see section 12) at unsignalled intersections on roundabouts. This is because a circulating vehicle has priority over those entering. If it stops to avoid obstructing the box when its exit is blocked, thereby releasing the flow of entering vehicles, there is likely to be uncertainty over re-establishing right of way when the exit is clear again. Moreover, a vehicle stopped in an outer lane might obscure vehicles lawfully continuing to circulate on the inner lanes (whose exit might not be blocked) from the view of drivers entering the roundabout. Yellow box markings may however be used where traffic entering the roundabout is controlled by signals at all times.
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