Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade separated and compact grade separated junctions) dn-geo-03060

Yüklə 8,57 Mb.

Pdf görüntüsü

səhifə	50/50
tarix	07.11.2018
ölçüsü	8,57 Mb.
	#78792

1 ... 42 43 44 45 46 47 48 49 50

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 169
Design of Channelising Islands
This appendix outlines the methodology for deigning channelising islands at priority junctions and is
subdivided into:

  T-Junctions or staggered junctions;

  Skew junctions; and

  Rural Crossroads.
T-Junctions or Staggered Junctions
The recommended layout for T-junctions or staggered junctions, where the minor road centreline is
inclined to the major road at an angle of between 70° and 110°, is shown in Figure B.1. This figure
should be read in conjunction with Tables B.1 and B.2.
Figure B.1: Design of Rural Channelising Island (Dimensions in Metres)

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 170
Table B.1: Channelising Island Offset
Minor road inclination (°)
Offset d (m)
70
1.5
80
2.0
90
2.5
100
2.0
110
1.5

Table B.2: Design of Radius R1
Width of major road carriageway at junction
(m)
Radius R1 (m)
9.5
12
10.0
12
11.0
14
Note:
Radius R2 is normally the same value as R1 but should be designed to ensure that the channelising island nose is
positioned between 2m to 4m from the edge of the main carriageway and that the width of the island lies between 2m and 5m.

The methodology for designing channelising islands of this type is described in the following sections
and represented in Figures B.2a to B.2f.

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 171
Figure B.2a: Channelising Island Development Steps 1 to 4

1.  Draw an offset, d, from the centreline of the minor road. Values for d are given in Table B.1.
2.  Draw circular arc, R1, tangential to the offset d from the minor road centreline and tangential
to the offside edge of the through traffic lane on the major road into which right turning traffic
from the minor road will turn. Values for Radius R1 can be found in Table B.2.
3.  By striking a circular arc of radius (R1 + 2) metres from the same centre point as arc R1 to
intersect the edge of the major road carriageway, Point X is established.
4.  Point Y is located where a straight line drawn from the centre point of arc R1 to Point X
crosses arc R1.

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 172
Figure B.2b: Steps 5 and 6

5.  Draw an arc, R2, through Point Y and tangential to the offside edge of the major road offside
diverging lane and of an equal radius to R1. (Note: Radius R2 is typically the same size as
R1 but should be designed to ensure that the channelising island nose is positioned between
2 to4m s from the edge of the main carriageway and that the overall width of the
channelising island is between 2m to5m.)
6.  Draw a point, Z, 40m from the edge of the major road on the centreline of the minor road.

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 173
Figure 9.1
Figure B.2c: Step 7
Figure 9.2

7. Draw 2 lines, A-A & B-
B, from this point, Z, which are tangential to the Arc’s R1 and R2.

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 174
Figure 9.3
Figure B.2d: Steps 8 to 10

8.
Offset these lines A-A and B-B by 0.3m inwards creating A1-A1 and B1-B1.
9. R1s and R2t are then created tangential to these offset lines A1-A1 and B1-B1.
a)
Arc R1
s
is created with radius equal to R1 and is tangential to B
1
-B
1
along the
minor road and the through traffic lane on the major road into which right turning
traffic from the minor road will turn
b)
Arc R2
t
is created with radius equal to R2 and is tangential to A
1
-A
1
and the offside
edge of the major road offside diverging lane.
10. Draw another line, C-C, which starts at a distance 25m up from the edge of the carriageway
on the centre line of the minor road and is tangential to the Arc R1s.

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 175
Figure B.2e: Steps 11 to 12

11.  Draw a 0.75m radius, R3, where R1
s
and R2
t
intersect near the major carriageway.
This is the bottom of the channelising island. R3 will be tangential to R1
s
and R2
t
.
12.  Draw another 0.75m to1m radius, R4 between line A
1
-A
1
and line C-C.  R4 will be
tangential to the Line A
1
-A
1
and C-C.

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 177
Skew Junctions
The design of channelising islands for skew junctions is similar to that outlined above, but the following
points should be noted:-
a)
The centreline of the minor road is turned with a radius of at least 50m to meet the
edge of the major road at right angles.
b)
For left hand envelope junctions, the channelising island should be about 15m
long. The right hand side of its tail (viewed from the minor road approach) should
touch the curved minor road centreline and be rounded off at a radius of 0.75m to
1.00m.
c)
The offset, d, for left hand envelope junctions is 4.5m.
d)
For right hand envelope junctions, the circular arc R1 touches the curved minor
road centreline and is tangential to the offside edge of the through traffic lane on
the major road into which right turning traffic from the minor road will turn.
e)
The channelising island should be about 15m long. The tail is offset about 1m to
the right of the curved minor road centreline (viewed from the minor road
approach) and rounded off with a radius of 0.75m to 1.00m.
Crossroads
The use of rural crossroads is regarded as a Departure from Standard. However for upgrading of rural
cross-roads the following details may be used.
The  recommended  layout  of  channelising  islands  at  rural  crossroads  where  long  vehicles  are
predicted, and where the minor road centreline is inclined to the major road at an angle between 70°
and 110°, is shown in Figure B.3.
There  are  similarities  in  the  design  to  that  outlined  previously,  but  the  following  points  should  be
noted:-
a)
The long axis of the channelising island is inclined at 5° to the minor road
centreline and the island is always 3m wide.
b)
The circular arc R1 has a radius of 11m and is tangential to the left hand side of
the channelising island (viewed from the minor road approach) and the centreline
of the major road. (In some cases where the minor road is inclined to the major
road at angles between 100° and 110°, R1 will have to be reduced to 8m to create
a suitable island.)
c)
The circular arc R2 has a radius of 11m and is tangential to the major road
centreline and the minor road centreline.
Where the minor road centreline is inclined to the major road at angles less than 70°, R1 will normally
be 12m and R2 8m.
Where  the  minor  road  centreline  is  inclined  to  the  major  road  at  angles  greater  than  110°,  R1  will
normally be 8m and R2 12m.
Where two envelope minor roads meet at a crossroads, the minor road centrelines should be offset
relative to one another by approximately the width of one channelising island.

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 182
Table D.1: Junction Analysis Procedure Worked Example

Junction Analysis Procedure
Date: 01/04/17
Project: N200 Junction Upgrade
Location: N200 / R999 Junction
Data Collection
Classification and
Name
AADT
Design
Speed
(Km/h)
Posted
Speed
(Km/h)
Current Year
(2016)
Design Year
(N/A)
Major Road
National Secondary
Road N200
4,000
6,000
100
100
Intersecting Road
Regional Road R999
3,200
4,500
100
80
Junction Type

                      New     Existing   
Site Visit
Yes: 
No: ____
Date of Site Visit (if applicable):   01/10/2017
Functional Characteristics
Part 1 (General Information for all Intersections)
Collision Analysis
Table 1 presents a summary of the accidents which have occurred at the N200/R999
Junction.  This information is also shown graphically in Figure 1.
Table 1:  N200/R999 Junction Collision Data
Number
Accident
date
Time
Location
Description
Severity
1
2010
11:30
Saturday
R99 (S)
80 kph zone, Car, Rear
end, straight, Dry
Minor
2
2010
15:35
Friday
N200/R999
100 kph zone,
Goods vehicle, Other
circumstances, Dry
Minor
3
2009
01:05
Thursday
R999 (S)
80 kph zone, Car, Single
vehicle only, Dry
Minor
4
2008
18:00
Tuesday
N200/R999
100 kph zone, Bus, Head-
on right turn, Wet
Minor
5
2007
16:00
Saturday
N200 (W)
100 kph zone, Car, Single
vehicle only, Dry
Minor
6
2005
16:30
Friday
N200/R999
100 kph zone, Other
vehicle, Angle, both
straight, Dry
Serious

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 183
Figure 1: Accident statistics at the N200/R999 junction

Access Requirements (Including
NMU Requirements and Level of
Usage)
No pedestrian or cycle facilities required at the junction.
Access Control
Priority controlled junction
Future Development
No planned future development in the area. Surrounding lands are zoned agricultural.
Vehicle Design Type (Include any
Special Design Vehicle Details)
Junction designed to accommodate a maximum vehicle size equating to a standard
articulated vehicle.
% HGV’s
4%

Part 2 (Specific Information for More Detailed Analysis)
Junction Layout & Turning
Movement Diagram

Figure 2: Friday morning peak hour junction turning movements

Figure 3: Friday evening peak hour junction turning movements

Notable Constraints due to
Upstream/Downstream Junction
Yes: ____
No: __
Notes:
Proposed Improvements to Other
Roads (that would impact the
traffic movement at this location)
None

Geometric Characteristics

Road Geometry on all approaches
To be attached in an appendix to this document.

Is design compliant with the
standards
Yes: ____

R999

29

125

195

265

25

224

16

28

N200

182

150

146

140

N200

19

150

5

175

271

15

106

R999

19

R999

30

119

282

165

27

130

8

20

N200

169

218

130

171

N200

38

240

3

281

157

11

153

R999

7

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Page 184
Desirable Stopping Sight Distances
200m
Achievable Stopping Sight
Distances
300m
Mainline Horizontal Curvature

Profile gradient on mainline
__________________2%
Intersecting Roadway
_____________2%
Other Characteristics

Traffic Management Measures
n/a
Impact on Utilities
n/a
Impact on Right of Way
n/a
Recommendation of Type of
Junction Treatment based on
Functional, Geometric and Other
Characteristics

The option to introduce a roundabout at the N200/R999 junction is considered to be the
emerging preferred option at this location. The assessment shows that this upgrade would
operate well within capacity, and is appropriate considering the relatively balanced flows
along each of the N200 and R999. In particular, this option allows for the safe movement of
vehicles along the R999 travelling across the, which in the staggered arrangements would be
required to undertake two movements to pass through the junction. A roundabout option
would also provide safety improvements.
Scope of Modelling Required
Local Junction Modelling     Micro-simulation Modelling  
Designer: Jane Smith                               Date: 01/04/17

Approved:____________________                 Date:________________

TII Publications
DN-GEO-03060
Geometric Design of Junctions (priority junctions, direct accesses, roundabouts, grade
separated and compact grade separated junctions)
April 2017

Yüklə 8,57 Mb.

Dostları ilə paylaş:

1 ... 42 43 44 45 46 47 48 49 50