Traffic island types | Function of the traffic island, Design Considerations

What is Traffic Islands?

An island is a defined area between traffic lanes for control. of vehicle movements. Within an intersection area, a median or an outer separation is considered to be an island. They minimize areas of major and minor conflict. Island establish physical channels through which vehicular traffic may be guided to travel and avoid conflict. There are different types of the traffic islands.

Traffic Island | Classification of Islands | Function of traffic island
Fig:- Traffic island

Traffic island types

Traffic islands usually serve more than one function, but maybe generally classified into four separate types:

1) Channelizing Islands

These are designed to control and direct traffic movement, usually turning. They are very useful for intersections at grade, particularly when the area is large. The size and shape of channelizing island will vary much depending upon the layout and dimensions of the intersection.

2) Divisional Islands

These are designed to divide opposing or same direction traffic streams, usually through movements.

3) Pedestrian islands

Pedestrian islands are provided to serve as safe zones for the aid and protection of persons on foot. If a divisional island is located in an urban area where pedestrians are present, portions of each island can be considered a refuge island.

4) Rotary island

This is the large central island of rotary intersection. This helps to convert crossing manoeuvre to weaving by providing sufficient weaving length.

Design Considerations for Traffic Islands

The total design of traffic islands can be studied in three steps:

Traffic Island | Classification of Islands | Function of traffic island

A) Selection of appropriate island type:

The site and traffic conditions in each intersection are different and hence the island type suitable for each requires separate attention.

The traffic island selected varies from barrier type islands to flush islands marked on the roadway surface.

B) Determination of shape and size of islands:

The shape of the island and its size in an intersection depends on the geometry and space availability at the same. A proper shape and size of the island (in the case of raised islands) must be selected so that it is able to both channelized the traffic and not pose any type of hazard.

C) Location relative to adjacent traffic lanes:

The islands must be offset from the roadway by some distance to remove the risk of a vehicle dashing against the same. The width of offset is maximum at the entry of the island and decreases gradually as one move towards the end of it.

Function of traffic island

  • They segregate vehicular traffic from pedestrian traffic.
  • They reduce the conflict area.
  • They segregate traffic into specification paths.
  • They increase traffic safety.
  • They increase the traffic capacity of the road.

I hope this article remains helpful for you.

Happy Learning – Civil Concept

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