Sunday, January 12, 2014

Traffic signs and Rotary intersection - (Traffic Engineering)

Traffic Signs:

These should be mounted on sign posts pointed alternatively with 25 cm black and white band.


  • Regulatory signs: These are used to inform road users of certain laws, regulations and prohibitions.


  • Warning signs: These are used to warn the road users of certain hazardous conditions that exist on or adjacent to the roadway. Shape of these are equilateral triangles with its open pointing upwards.

  • Informatory signs:  These signs are used to guide the road users along to make travel easier, safe and pleasant. Informative signs are grouped under following sub-heads:
  1.  Direction and place identification signs.
  2. Facility information signs.
  3. Other useful information signs.
  4. Parking signs.
  5. Flood gauge.

Conditions when traffic rotary is justified:

American Association of State highway officials(AASHO) have suggested that lowest limit of traffic volume when a traffic rotary is justified is about 500 vehicles per hour or all intersecting roads put together and maximum limit beyond which the rotary may not efficiently function is about 5000 vehicles per hour. IRC suggests that maximum volume of traffic that a rotary can efficiently handle is 3000 vehicles per hour entering from all the legs of the intersection. Traffic rotary angles may be provided where intersecting motor traffic is about 50% or more of the total traffic or all intersecting roads or where the fast traffic turning right is at-least 30% of the total traffic.

What is traffic rotary?

Traffic rotary is an enlarged road intersections where all converging vehicles are forced to move round a large central island in one direction before they can weave out of traffic flow into their respective directions radiating from the central island.

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