Module 6 : Traffic Intersection Control
Lecture 31 : Channelization
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Numerical example 1

Provide Channelization for an intersection having EW as the major road. The major and minor roads intersect at right angles. The design vehicle is WB-50 (R=25m) and design speed is 45 kmph. The intersection is unsignalized. EW road has 2 lanes in each direction and NS has 1 lane for each direction. Take lane width =3.6 m. Provide bullet nose median ends. Also provide channelizing island for free right for WS bound traffic.

Solution

: The approach taper for auxiliary lane is equal to $ 3.6 \times 45 \times 45/100 = 73~m$. The deceleration Taper is taken as 40 m. Considering a 1:10 taper, the Bay Taper is found out to be 18 m. Let the storage length = 30 m (say). Now from Table. [*], it is found that for bullet nose median end, Median Opening = 30 m. The dimensions of all the components of the auxiliary lane are shown in Fig. 1.
Figure 1: Dimensions of components of the auxiliary lane for the intersection
\begin{figure} \centerline{\epsfig{file=qfChanAuxiliaryLaneD.eps,width=8cm}} \end{figure}
The width required for the WB- 50 semi-trailer unit is found to be about 6.5 m. Additional 0.5 m is provided on the outer side and 0.3 m is provided on the inner side away from the edge of the island. For the turning roadway for the W-S direction, the single offset method is used. At 0.3 + 0.5 + 6.5 = 7.3 m from the island edge, a circle of radius 25 m is laid out. Then two tapers of slope 1:15 is laid out on either side of the arc to join with the straight edge on either side. Thus the Channelization is provided for the W-S approach. Similar method can be used for designing the Channelization schemes of the other directions as well. The Channelization for the W-S approach is shown in Fig. 2.
Figure 2: Channelization for the W-S direction with traffic island
\begin{figure} \centerline{\epsfig{file=qfChanWSdirection.eps,width=8cm}} \end{figure}

Numerical example 2

Following the principles of Channelization suggest suitable island schemes for the following intersections (considering both high relative speed and low relative speed) (Figs. 3,  4)

Solution

  1. Y – Intersection (Figs. 5,  6 and 7)
  2. Skewed intersection (Figs. 8,  9 and 10)
Figure 3: Wye Intersection
\begin{figure} \centerline{\epsfig{file=qfChanWyeIntersection.eps,width=8cm}} \end{figure}
Figure 4: Skewed Cross Road
\begin{figure} \centerline{\epsfig{file=qfChanSkewedCrossRoad.eps,width=8cm}} \end{figure}
Figure 5: (a) Y - Intersection
\begin{figure} \centerline{\epsfig{file=qfChanIntersectionYa.eps,width=8cm}} \end{figure}
Figure 6: (b) Y - Intersection
\begin{figure} \centerline{\epsfig{file=qfChanIntersectionYb.eps,width=8cm}} \end{figure}
Figure 7: (c) Y - Intersection
\begin{figure} \centerline{\epsfig{file=qfChanIntersectionYc.eps,width=8cm}} \end{figure}
Figure 8: (a) Skewed Intersection
\begin{figure} \centerline{\epsfig{file=qfChanIntersectionSkeweda.eps,width=8cm}} \end{figure}
Figure 9: (b) Skewed Intersection
\begin{figure} \centerline{\epsfig{file=qfChanIntersectionSkewedb.eps,width=8cm}} \end{figure}
Figure 10: (c) Skewed Intersection
\begin{figure} \centerline{\epsfig{file=qfChanIntersectionSkewedc.eps,width=8cm}} \end{figure}