Module 6 : Traffic Intersection Control
Lecture 31 : Channelization
1 2 3 4 5 6 7 8 9 10 11 12 13
 

Objectives

The use of Channelization is often creative and innovative, providing for vehicle path separation and distinct and thus in general making traffic flow safer, smoother, simpler and efficient. The main objectives of Channelization can be summarized as follows:
  1. Separation of maneuver areas: The drivers should be presented with only one decision at a time to reduce confusion and the influence of operations caused due to the overlapping of maneuver areas.
  2. Reduce excessively large paved areas: The spread of the paved area can be considerably reduced by the construction of raised islands and medians where these are considered safe and necessary.
  3. Control of maneuver angle:The intensity of accidents can be reduced to a large extent by providing small angles for merging, diverging and weaving (at low relative speeds) and approximately right angles for crossing (at high relative speeds). The maneuver angle can be easily controlled by constructing islands of appropriate shapes and sizes.
  4. Favor predominant turning movements: Channelization is also directed for giving preference to turning movements at an intersection where the proportion of such traffic is high.
  5. Control of speed: Channelization is also used for supporting stop or speed regulations by removing differentials in speed for merging, diverging, weaving and crossing by using the bending and funneling techniques.
  6. Protection and storage of turning and crossing vehicles: To shadow slow or stopped vehicles from other traffic flows.
  7. Blockage of prohibited movements: Proper Channelization also helps maintain traffic regulations by making prohibited movements impossible or inconvenient.
  8. Provide space for traffic control devices: To provide space for traffic control devices when the ideal location for the same is within the intersection area.
  9. Segregation of non-homogeneous flows: Channelization provides separate channels for turning and through, fast and slow, and opposite direction traffic.
  10. Protection of pedestrians and reduction of crossing distances between refuses: Non-traversable and wide medians provide a refuge for pedestrians crossing a street.
Consider for example the T-intersection shown in Figs. 1, 2, and  3. In Fig. 1, the intersection has no special Channelization for helping drivers in avoiding conflicts between movements. In Fig. 2, a passing lane for through vehicles in the eastbound direction and a westbound right-turn lane has been added, which helps in separating the turning traffic from the through ones. In Fig. 3, the use of lanes is further clarified due to the addition of channelizing islands.
Figure 1: Illustration of T-intersection Channelization, (a)Intersection with no Channelization
\begin{figure} \centerline{\epsfig{file=qfChanNoChannelization.eps,width=8cm}} \end{figure}
Figure 2: Illustration of T-intersection Channelization, (b)Intersection with right-turn and passing lane
\begin{figure} \centerline{\epsfig{file=qfChanPassingLane.eps,width=8cm}} \end{figure}
Figure 3: Illustration of T-intersection Channelization, (c)Fully channelized intersection
\begin{figure} \centerline{\epsfig{file=qfChanFullyChannelized.eps,width=8cm}} \end{figure}