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T.P.D.M.V.2.4
APPENDIX 3
Examples of Weaving Section Calculations
Example 1
A new road is to be constructed within an existing urban area with a
design speed of 50 km/h and a design flow of 1600 v.p.h. per lane* Over
one particular section the weaving section length between an entry and the
adjacent exit is limited by connections to the existing road network to
200m.
The predicted design year flows in vehicles per hour are :-
Qnw1 s major non weaving flow s 1500 v.p.h.
Qnw2 = minor non weaving flow =
600 v.p.h.
Qw1 = major weaving flow = 1000 v.p.h.
Qw2 s minor weaving flow s 800 v.p.h.
Qw1
Qnw1
"800
1500
The average gradient through the section and 0.5 km upstream of the merge
is 1J uphill and the predicted heavy vehicle content is 2555. From Table
4.6.8.1 therefore the predicted flow should be adjusted by 4-855 resulting
in the following adjusted flows :-
Qnw1 r 1620, Qnw2 = 648, Qw1 - 1080, Qw2 s 864
The total weaving flow is thus 1944,
From Diagram No. 4.6.10.4 using line C~C (for urban conditions)
Lmin = 170m (H.B. this is greater than the absolute minimum figure
indicated in the small graph inset of Dia. 4.6.10.1}
Number of lanes required within weaving section :-
Qnw1 + Qnw2 + Qw1
Lmin
X Lact *
1)
Qw2
Where D = design flow per lane
and Lact s actual weaving length