1 - HKU Libraries

T,P*D.M*V.2*4
4.6.10 Weaving Sections
4.6*10.1 The following paragraphs cover the design of all true weaving
sections, that is to say those areas where traffic streams, each
moving in the same general direction, cross each other by
successive merging and diverging manoeuvres. Such areas may
occur on carriageways between adjacent junctions, between
successive entry and exit slips and on links within free-flow
interchanges. The advice does not cover what are at times
wrongly referred to as weaving sections within roundabouts*
4,6.10*2 In essence the design procedure involves the assessment of the
length and width of weaving section required to cater for the
predicted design year flows* The minimum weaving section length
is determined from consideration of the weaving flows and the
design characteristics of the road* Based on the minimum and
actual weaving section lengths the weaving section width is
derived* Each step of the procedure is described in the
following paragraphs and illustrated with examples in Appendix
3.
4.6*10*3 Predictions are made of the peak hour design year traffic
volumes* These traffic volumes are required in the form of non
weaving (Qnw), major weaving (Qw1) and minor weaving (Qw2)
components as illustrated below :-
-»*. Qnwl
iwt
;
iw2
•^ Qnw 2
Qnw * Qnw1 + Qnw2
These traffic volumes are adjusted for non standard traffic
composition and gradient using Table 4.6.8.1* The gradient
should be measured over the approximate length of the weaving
section plus a distance upstream of the weaving section up to
0.5 km in length*
4.6*10*4 The minimum weaving length based on the total weaving flow (Qw1
+ Qw2 adjusted) is given by reference to Diagram 4.6*10.1* Line
A should be used for very high standard rural roads with high
design speeds around 100 km/h and consequently low design flows
around 1200 v.p.h. per lane. Line B should be adopted for the
more normal standard of high capacity road in Hong Kong with a
design speed around 80 km/h and a design flow of 1400 v.p.h* per
lane* Line C represents the urban condition with low design
speed around 50 km/h and consequently higher design flow of 1600
v*p*h. per lane.
The minimum weaving section length derived as above should be
compared with the minimum weaving section length indicated by
the small graph, related to design speed alone, and the larger