TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017
Page 48
5.6.3.8
Visibility at Cycle Route Junctions
Where
the minor road is a cycle route, the required ‘x’ distance on the cycle facility on the approach
to a road shall be as set out in Table 5.6 and Figure 5.18.
The appropriate ‘y’ distance depends on the design speed of the major road, as set out in Table 5
.5.
Figure 5.18: Visibility envelopes for junctions with roads and crossings of roads
Table 5.6: Values used as set back distances (X) from edge of carriageway
X
–
distance (m)
Description of Use
4.0
Cycle route approach to a road
–
Desirable Minimum
2.0
Cycle route approach to a road
–
Absolute Minimum
Where a cycleway or track intersects with another cycle facility the required visibility envelope is
dependent on the design speed of the cycle facility and the ‘Y’ distance is that presented under in
Table 5.7 for Minimum Stopping Sight Distance.
Table 5.7: Stopping Sight Distances
Design Speed (km/h)
50 km/h
30 km/h
10 km/h
Minimum Stopping Sight
Distance (m)
60
35
15
TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017
Page 49
5.6.4
Approach Gradients
Gradients on minor roads shall be in accordance with DN-GEO-03031. On direct accesses, gradients
greater than 10% approaching the major road are a Departure from Standard. The gradient on the
minor road immediately next to the major road should be considerably less, and a "dwell" area of at
least 15m shall be provided immediately adjacent to the major road carriageway. Where site
conditions are particularly difficult this area may be reduced to 10m as a Relaxation. In the case of a
direct access to dwellings, it may be reduced to 3m as a Relaxation. A combined relaxation in dwell
area and approach gradient is not regarded as a departure.
The gradient for the dwell area shall lie between plus and minus 2.5%. In difficult situations this may
be increased to between plus and minus 4% as a Relaxation.
5.6.5
Corner Radii
It is recommended that the minimum circular corner radius at simple junctions in rural areas where no
provision is made for HGVs should be 10m. Where there is frequent use by large commercial vehicles
(e.g. near a quarry or industry frequently accessed by large vehicles), the minimum circular corner
radius shall be as follows:
a)
For vehicles entering the minor road, the corner radii shall be 13m followed by a
1:10 taper for a distance of 25m measured along the line of the minor road from
the nearside edge of the major road.
b)
For vehicles entering the major road from the minor road, the corner radii shall be
13m followed by a 1:10 taper for 25m measured along the line of the major road
from the corner line of the minor road. This is shown in Figure 5.19.
c)
13m at ghost island junctions and Type 3 Dual Carriageway priority junctions, with
tapers of 1:6 over a distance of 30m.
d)
13m at simple
staggered junctions, with tapers of 1:8 over a distance of 32m.
e)
20m radius for left-in/left-out priority junctions.
f)
40m radius for left in-left out priority junctions forming part of a compact grade
separated junction.
The values in a) to d) above are minimum values and a swept path analysis shall be carried out in
accordance with Chapter 4 at all at-grade junction locations to establish circular corner radii for the
junction appropriate for its use. In addition, the above minimum radii only apply where there are no
nearside diverge lanes.
Where HGVs comprise a significant proportion of the turning movements (e.g. where a quarry or
industry is located on the side road), use of the compound curve is recommended. Details of the
design of a compound curve are included in Appendix C of this document.