TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017
Page 154
8.2.9
Cross Sections and Curve Widening
For the purpose of designing junctions and interchanges, cross-sections for the mainline and typical
connector roads are given in DN-GEO-03031 and Chapter 7 of this standard. Different lane marking
details and widths of construction for connector roads are specified in this Standard. Compact
connector roads may be widened on curves in accordance with Table 8.2, the widening shall be
applied in the form of central hatched markings as illustrated in Figure 8.1. The width of curve widening
shall be chosen to suit the anticipated level of usage by HGVs. Designers shall take into account the
probability of HGVs regularly meeting on the curve.
Where no curve widening is applied HGVs will cut across into the oncoming lane, where the minimum
curve widening is applied HGVs will cut across into the whole of the hatched area. Where the
normal
curve widening is provided there will be sufficient width for two large vehicles to pass in opposite
directions. Regulatory signs shall be provided when appropriate in accordance
with the requirements
detailed later in this Chapter.
Figure 8.1: Application of Curve Widening
Table 8.2: Curve Widening on Compact Connector Roads
Inner Channel Radius
(m)
Width W
H
of Hatching at Apex on Curve (m)
No Curve Widening
Minimum Curve
Widening
Normal Curve
Widening
40
0.6
1.90
3.40
32
0.6
2.54
3.74
Carriageway widths for the compact connector road shall be such that they provide a transitional
change in standards from the major carriageway width to the minor carriageway width in accordance
with Table 8.3.
The minimum width of carriageway for a compact connector road shall be 6.6m and the maximum
shall be 7.9m, excluding curve widening. Where the traffic volumes are particularly low and the
proportion of HGVs is correspondingly low a relaxation to 6m may be permitted, by either reducing
the carriageway width or omitting the central hatched markings.