Transportation Engineering - Vol 2 | 19. Traffic Rotaries by Abraham | Learn Smarter
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19. Traffic Rotaries

Traffic rotaries are designed to streamline traffic flow by converting severe intersection conflicts into milder ones, promoting safer vehicular movement. This chapter discusses the benefits and limitations of rotaries, guidelines for their selection, operational characteristics, design elements, and capacity assessments. The design principles ensure efficient traffic management, especially in areas with moderate traffic volumes and varied movement patterns.

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Sections

  • 40

    Traffic Rotaries

    Traffic rotaries, or roundabouts, facilitate orderly traffic flow by forcing vehicles to navigate in one direction around a central island, reducing severe intersection conflicts.

    Learning Practice

  • 40.1

    Overview

    Rotary intersections, also known as roundabouts, facilitate one-way traffic flow around a central island, significantly reducing the severity of conflicts typical at traditional intersections.

    Learning Practice

  • 40.2

    Advantages And Disadvantages Of Rotary

    Rotary intersections offer benefits such as improved traffic flow and reduced accidents, but also present some drawbacks like cumulative delays and cost implications.

    Learning Practice

  • 40.3

    Guidelines For The Selection Of Rotaries

    The guidelines for selecting rotaries focus on ensuring suitable traffic volumes and distributions for efficient flow.

    Learning Practice

  • 40.4

    Traffic Operations In A Rotary

    This section discusses the key traffic operations at rotary intersections, focusing on diverging, merging, and weaving movements.

    Learning Practice

  • 40.4.1

    Design Elements

    This section covers the essential design elements crucial for effective rotary intersections, including design speed, dimensions of the central island, and various widths.

    Learning Practice

  • 40.4.2

    Design Speed

    The design speed for traffic rotaries is significantly lower than that of the roads leading to it, usually set at 30 km/h for urban areas and 40 km/h for rural areas to ensure safety and efficient traffic flow.

    Learning Practice

  • 40.4.3

    Entry, Exit And Island Radius

    This section discusses the design considerations for entry, exit, and island radii in traffic rotaries, focusing on speed and safety.

    Learning Practice

  • 40.4.4

    Width Of The Rotary

    This section discusses the design considerations for the width of rotaries, focusing on entry and exit widths in relation to traffic flow.

    Learning Practice

  • 40.5

    Capacity

    This section outlines how to determine the capacity of rotary intersections through empirical formulae, focusing specifically on the capacity of weaving sections.

    Learning Practice

  • 40.6

    Summary

    Traffic rotaries reduce crossing complexity by promoting weaving operations among vehicles.

    Learning Practice

  • 40.7

    Problems

    This section presents a problem related to capacity calculation of a rotary intersection based on given traffic data from four approaches.

    Learning Practice

References

40.pdf

Class Notes

Memorization

What we have learnt

  • Rotaries help to eliminate ...
  • Design elements such as ent...
  • Capacity of a rotary is det...

Final Test

Revision Tests