7MAJOR/ MINOR JUNCTIONS
SIMPLE JUNCTIONS
7.1 Figure 7-1 illustrates the layout of simple T-junctions. Guidance on the use of Give Way lines(diagram 1003) can be found in paras 3.14 to 3.23, on warning lines (diagrams 1004 / 1004.1) in paras 4.12 to 4.26 and on edge lines (diagrams 1009 and 1010) in paras 4.28 to 4.30. Table 7-1 gives details of the warning line, road studs and the minimum number of marks to be used where practicable. This number may not always be achievable on the minor road if this is narrow.
GHOST ISLAND JUNCTIONS
7.2 Ghost island junctions are usually provided to afford right-turning vehicles some protection and assist free flow of major road through traffic.
7.3 The use of ghost islands on unrestricted rural single carriageway roads can sometimes pose safety problems. Where overtaking opportunities on the major road are limited, the presence of a widened carriageway, albeit with hatched markings, might result in overtaking manoeuvres which conflict with right turns into and out of the minor road. Where this proves to be a problem, consideration should be given to the use of kerbed islands to prevent overtaking and to guide traffic through the junction. Alternatively, double white lines as described in paras #7.11 and #7.12 may be used.
7.4 The through lane in each direction ((c) in figure 7-2) should not be more than 3.65 m wide, exclusive of hard strips, nor less than 3 m. The desirable width of the turning lane (d) is 3.5 m, although this may be reduced to 3 m (but see para #7.5). At urban junctions it can sometimes be advantageous to use a wider turning lane, not exceeding 5 m. This provides some degree of shelter in the centre of the road, helping vehicles turning right from the minor road to make the turn in two separate stages. On rural roads, with speeds above85kph (50 mph), or where hard strips are present, widths greater than 3.65 m are inadvisable because wide ghost islands in these situations create a sense of space which could encourage overtaking at hazardous locations. Where space is very limited, a reduced width may be unavoidable. In such cases the width of ghost islands should not be less than 2.5 m, except as described in para 7.5.7.5 On narrow urban roads it might not be possible to provide full width right-turning lanes. It might still be worth offsetting the main road centre line towards the minor road and using hatched markings to diagram 1040, even if the hatched width is less than 2.5 m. This can create space to help ahead traffic pass right-turning vehicles and make the junction more conspicuous. However, this technique is not appropriate where the speed limit is more than 30 mph, or the carriageway is less than 7.3 m wide. No through lane should be narrower than 3 m.
| Diag No. |
Speed limit (mph) |
Mark (m) |
Gap (m) |
Width (mm) |
Spacing of studs if used (m) |
Minimum number of marks on each approach | ||
|---|---|---|---|---|---|---|---|---|
| Speed limit(mph) | ||||||||
| Over 40 |
40 | 30 | ||||||
| 1004 | 40 or less |
4 | 2 | 100 (see note) |
6 | – | 7 | 5 |
| 1004.1O | Over 40 | 6 | 3 | 100 (see note) |
9 | 7 | – | – |
NOTE: The width should be increased to 150 mm if the road is 10 m or more in width with no ghost island.
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