TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017
Page 32
Problems have been experienced with priority junctions where the major road is on a curve and the
minor road is at an acute angle, which can be misleading to drivers who perceive
that the minor road
retains priority. In such circumstances, the minor road approach should be re-aligned to connect to
the major road at 90˚ in order to eliminate any driver confusion as to which route
has priority.
Figure 5.2: Examples of minor road alignment at junctions
The provision of new priority junctions or direct accesses on minor roads shall not be permitted within
90m of a roundabout or priority junction on national roads; this may be reduced to 50m as a relaxation
on Regional and Local roads. See figure 5.3.
Figure 5.3: Clearance to minor road/junction at roundabout or priority junction
TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017
Page 33
5.2.3
Vertical Alignment
New or altered junctions and accesses at or near crests should be avoided where the shape of the
junction or access would not be immediately apparent to the driver on the national road, or where
there is restricted forward visibility.
Care should be taken not to provide visibility on minor roads much in excess of the desirable minimum
as this can divert the driver's attention away from road users on the major road in the immediate
vicinity towards those approaching in the far distance.
It is also essential that other road users can equally see oncoming vehicles; particularly where vehicles
cross the raised footway in front of pedestrians/cyclists.
5.2.4
Visibility
At driver's eye level there shall be a clear view from the junction or access over the immediate area
of the junction or access and its connection to the national road.
Direct accesses shall only be sited where they do not encroach on the visibility requirements of
adjoining direct accesses or junctions in regular use. This will determine the minimum spacing of new
accesses. However a minimum staggered distance of 20m shall be provided at all times.
Signs, street furniture and planting should be located and designed so as not to obstruct visibility.
5.2.5
Junctions and Direct Accesses on Climbing Lanes
Priority junctions and direct accesses to national roads shall not be located on climbing lane sections.
5.3
Priority Junction Layouts
Table 5.1 shows the priority junction forms considered suitable for various major road carriageway
types in rural situations. This table should be used as a starting point in choosing the most appropriate
type of priority junction to use at a particular site.
Table 5.1: Possible junction types for different major road carriageway types
Junction/Direct Access Type
Carriageway Type
Simple (Fig. 2/1)
Ghost Island (Fig. 2/4)
Standard
╦
╦╩
╬
╦
╦╩
╬
Single Carriageway
Yes
Yes
No
Yes
Yes
No
Type 1 Dual
Yes†
No
No
No
No
No
Type 2 Dual
Yes†
No
No
No
No
No
Type 3 Dual
Yes†
No
No
Yes†
No
No
Motorway
No
No
No
No
No
No
╦ T
-Junction
╦╩ Staggered Junction
╬
Crossroads
† Left in/left out junctions
and direct accesses only (see DN-GEO-03031 for more details by road type)
Simple junctions (such as the simple T-Junctions ) are appropriate for most minor junctions on single
carriageway roads but left in/left out junctions are the preferred option as they reduce conflicts on the
national road network. On dual carriageways simple junctions shall be restricted to left in/left out only,
except at single lane sections of Type 3 Dual Carriageways where a right turning facility off the major
road (see Figure 5.28) may be provided as a Departure from Standards. Right turn manoeuvres onto
the major road from the minor road shall not be permitted.
TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017
Page 34
The decision to provide a right turning facility shall be made in accordance with the guidance contained
in Chapter 4. The choice of type of right turn facility to be used, however, will depend on the particular
site characteristics and results of traffic modelling of the turning movements at the junction.
5.3.1
Simple Priority Junction
Where a simple priority junction is provided on a single carriageway road with no hard shoulders, a
nearside passing bay as detailed in Figure 5.4 shall be provided to allow through traffic on the major
road pass a vehicle waiting to turn right. The total length of the nearside passing may need to be
increased where it is anticipated that HGVs will be turning off the major road.
Figure 5.4: Priority Junction with Nearside Passing Bay for Roads without Hard Shoulders
5.3.2
Ghost Island
Ghost island junctions may be used on new single carriageway roads, or in the upgrading of existing
junctions to provide right turning vehicles with a degree of shelter from the through flow. They are
highly effective in improving safety for turning traffic on the major road.
The use of ghost island junctions on rural single carriageway roads can, in certain circumstances,
pose safety problems. In situations where overtaking opportunity on the major road on either side of
the junction is restricted, the presence of a widened carriageway, albeit with hatch markings, could
result in overtaking manoeuvres which may conflict with right turning movements into and out of the
minor road.
On single carriageway roads where overtaking opportunity is limited, ghost island junctions should be
sited on non-overtaking sections, as defined in DN-GEO-03031.