This document discusses the advantages of using roundabouts for traffic control from the perspective of Williams and Associates, an engineering firm based in Athens, Georgia. It outlines 7 key advantages of modern roundabouts: 1) safety, as they reduce conflict points and severity of accidents; 2) functional performance, as traffic flow is improved with continuous movement; 3) economic benefits from reduced maintenance costs and accidents; 4) environmental benefits from less idling and emissions; 5) traffic calming effects from lower design speeds; 6) aesthetic benefits from landscaping opportunities; and 7) improved pedestrian safety and access from lower vehicle speeds. The document provides an overview of roundabouts and their traffic control functions.

2. Hi, we are Williams and Associates,
your local Athens, Georgia based
engineering firm, here again with another
tip from our
“How to” series.

3. One of our specialties is traffic engineering,
and today I’ll be talking about the
advantages of using roundabouts for traffic
control.

4. OK, let’s get started… So,
what is a Roundabout?

5. Roundabouts, like traffic signals and stop
signs, control the flow of traffic at roadway
intersections.

6. Modern roundabouts have several
characteristics that differentiate them from
other circular roadway features such as
traffic circles and rotaries, which allow
high vehicle speeds, require large
amounts of land, and require circulating
traffic to yield to incoming traffic.

7. Unlike older circular roadways, modern
roundabouts have channelized approaches to
separate opposing traffic at the entry and exit
points, roadway curvature that promotes lower
vehicle speeds, counterclockwise circulation
around a central island to eliminate left turns and
reduce the number of vehicle conflict points, and
require entering traffic to yield to circulating traffic.

8. What are the 7 Advantages of a
Roundabout?

9. First, Safety—Modern roundabouts
eliminate through and left turn movements
and thus reduce the number of vehicle
conflict points, the angle of impacts, and
the resulting severity of injuries and
number of fatalities when compared to
those associated with stop-controlled and
signal-controlled intersections.

10. Second, Functional Performance—
Modern roundabouts do not require
entering and exiting vehicles to stop. All
approaches are yield-controlled which
reduces delay and congestion.

11. At stop-controlled and signal-controlled
intersections, opposing and cross traffic is
required to stop to allow the approach with
the right-of-way to proceed through the
intersection, while at a modern roundabout,
vehicles from all four approaches may
simultaneously enter the roundabout.

12. During off-peak hours, vehicles entering the
roundabout experience minimal delays as
there are fewer vehicles to which the entering
vehicles are required to yield; whereas,
vehicles in signal-controlled intersections may
sit through an entire signal cycle during the
off-peak hours even when there is no cross
traffic.

13. Third, Economic Impact—Modern
roundabouts use less electricity and have
fewer electrical components than traditional
signalized intersections.

14. Equipment maintenance that is required for
a traffic signal includes bulb replacement,
routine upgrades and replacements, and
software updates.

15. The reduction in accidents that occur at
roundabouts results in a reduction in
economic and social costs related to
property damage, physical injuries and
fatalities.

16. Fourth, Environmental Impact—Since
vehicles are not required to stop at the
approach to a modern roundabout, idle
time and stop and start movements are
reduced when compared to traditional
intersections.

17. With these changes in vehicle operation
patterns, users of the intersection will
experience reduced noise and air quality
impacts as well as reduced fuel
consumption.

18. Fifth, Traffic Calming—Modern
roundabouts are designed with specific
geometric patterns that encourage drivers
to reduce the operating speed of their
vehicles.

19. Signage at each approach to the
roundabout limits the speeds of vehicles
entering the intersection.

20. Sixth, Aesthetics—The central island and
splitter islands provide landscape
opportunities as well as serving as a
unique roadway feature that can be used
as a landmark or gateway feature for a
region or neighborhood.

21. And seventh, Pedestrian Access—
Pedestrian safety is provided at
roundabouts by reducing vehicle operating
speeds and providing pedestrian refuge in
the splitter island.

22. The refuge area allows pedestrians to
focus on approaching vehicles from one
direction at each stage of the crossing.

23. There you have it!
The Top 7 Advantages
of traffic roundabouts…

24. Good luck in your traffic engineering
projects, and if you’re ever in
Athens, stop by and see us.

25. Until next time, all the best from