What is a traffic island?
Traffic Island can be a physical structure or a painted object found on roads and road sides. The primary purpose of a traffic island is better & orderly flow of traffic. These are also referred to as channelizers as these “channelizes” the traffic plying on the road. These may be raised structures made up of concrete or a physical structure in form of boards, barricades, traffic cones etc.
It can also be regarded as a physical barrier various shapes for channeling the flow of tragic and reducing the number of conflict points. Their proper placement is of great importance and is a must know for a town planner as it plays an important role in transport planning.
When traffic island is much longer in length than width then they are instead called traffic medians (a strip in the middle of a road) serving the function of divider over a much longer distance.
Example & Use of Traffic Island
The examples include roundabout, triangular traffic islands or other shape solving the required purpose. These a serve additional purpose of providing the stopping space/refuge to pedestrians, space for signage, vegetation, hawkers/vendors, space for traffic signals and sometimes of fountains or statues. They are significant as they allow easy movement of vehicles along with providing space for proper queuing of vehicles. They act as lungs for intersections as due to large number of direction change resulting in increased pressure on vehicle’s part intersections are more polluted in comparison to other part of road. So a traffic island with vegetation over it reduces the carbon footprint for that intersection.
Design & geometrical considerations of traffic island
- Shape and size: The shape & size of traffic island is determined on the basis of function it is meant to serve. Like in case of median its much longer in length than width because its function is to divide the flow of traffic. In case of a channalizer the function of traffic island is to channelized the flow of traffic in a particular direction. These are sometimes elongated like in case of a channelizers. These can also be round like in case or rotatory and round about which are used for giving a larger maneuvering space to drivers.
- Location: Traffic island can be present on the side of road, across the road or even in mid way along the road. The functional classification of island is the most important determining factor of the location of a island.
- Island type: The deicision of using a painted, concrete structure, traffic cone etc rests with the transportation department and can be choosen as per the economics and the extent to which these fulfill the requirement. However if the traffic volume is substantial, concrete structure is generally used as it forces the user to follow it, painted lines work where people are law abiding and the flow of traffic is relatively less.
Classification of Traffic Islands
There are three main classifications involved based on the purpose they serve. The purposes served may be more than one depending on their geometry, location, size and shape.
- Channelizing Island: These go by the name and functions like a channelizer which provides direction to the vehicles. The most prominent use of this type is at the turning points, these allow smooth and easy turning of traffic and prevents interference with the other straight moving vehicles. These are also found where the roads converge or diverge as they helps in reducing conflict points and allow easy merging and diverging of traffic.
- Divisional Island: These are used along the roads. These are elongated structures which can be considered as median or divider but used for the traffic moving in the same direction. These also provide slip roads which are meant to bypass the traffic signal for straight moving vehicles. These are not meant to aid turning but helps in orderly movement of vehicles and might form a part of channelizing island which further assist in reducing conflict points.
- Refuge Island: These are large in size and are meant for pedistrians rather then the vehicles. These are provided to serve as a safe zones for walkers. These are raised structures large enough for a person or a group of people to stand. These can be located on a mid section of a road at point of pedestrian crossing as these provide a safe and raised surface where driver can see them and remain alert.