Roundabouts – FAQ’s

What is a roundabout?

A roundabout is an alternative form of intersection traffic control.  A modern roundabout is a circular intersection with yield at entry to promote safe and efficient traffic flow. They are gaining widespread use in North America, with implementation in several Canadian provinces and U.S. states. Typical characteristics of a modern roundabout include:

    • Yield at Entry
    • Slower Speeds
    • One-Way Travel around the central island (counterclockwise)

Roundabouts have the potential to reduce collisions, traffic delays and fuel consumption resulting in improved air quality through reduced vehicle emissions.  Roundabouts may be single or multiple lane – the Tyson Road roundabouts are planned as single lane.

How do roundabouts affect traffic flow?

Because approaching traffic only has to yield to vehicles already circulating in a roundabout, movement is often without delay. Roundabouts have proven to move traffic through an intersection at a much higher rate than traditional intersection controls.

How do roundabouts affect safety?

Modern roundabouts are proving to be the safest type of at-grade intersection since they decrease the possibility for crashes that involve serious injury because they reduce speed and the chance of head-on collisions.  Statistically, roundabouts are much safer for drivers and pedestrians than traditional intersections.  Roundabouts have shown to reduce fatal crashes by 90 percent, injury crashes by 75 percent, and pedestrian crashes by 30 to 40 percent.   The potential conflict points associated with both roundabouts and traditional intersections can be seen in the Figure 2 below.  Roundabouts have 8 conflict points vs. 32 on a signalized intersection.

A 2012 review of safety studies indicates that injury collisions have been found to be fewer in number and less severe for a roundabout than a signalized intersection in Australia, Belgium, New Zealand, the United States, the Netherlands, Norway and the United Kingdom. Injury reductions range from 25%-74%. The Region of Waterloo in Ontario has been installing roundabouts for over 10 years and has extensive data on their performance compared to the more traditional signalized intersection. Waterloo has monitored the average "Injury Collisions per year at Intersections converted to a roundabout" and noted a 70% reduction.

Are roundabouts safe for pedestrians?

Roundabouts are generally safer for pedestrians than traditional intersections. Pedestrians would cross the roadway only one direction of traffic at a time. Crossing distances are relatively short, and traffic speeds are lower than those encountered at traditional intersections. Single-lane roundabouts have been reported to involve substantially lower pedestrian crash rates than comparable intersections with traffic signals.  Pedestrians should watch for gaps in the traffic and choose a safe time to cross. 

The Region of Waterloo has also noted a reduction of collisions with pedestrians at roundabouts.  As an example; data collected between 2007 & 2011 shows:

  • 177 pedestrian collisions occurred at 246 signalized intersections (0.14 collisions per year per intersection); and
  • 4 pedestrian collisions occurred at 15 roundabout intersections (0.05 collisions per year per intersection).

Are roundabouts safe for cyclists?

The way cyclists operate through a roundabout depends on their degree of comfort and experience level with riding in traffic. More experienced cyclists may choose to circulate as a vehicle, merging into the travel lane before the bike lane or shoulder ends. Less experienced cyclists can dismount their bicycles and use the roundabout like a pedestrian would.

Is the cost of constructing a roundabout more than a traditional intersection?

Modern roundabouts are sometimes less expensive than traffic signals, particularly in the long run. Generally, the initial construction cost of a roundabout is similar to the initial construction cost of a signal, but because there are no traffic signals, equipment maintenance costs are less. As well, because traffic moves through a roundabout in a very efficient manner, it is possible that streets between roundabouts can operate well with fewer lanes, providing a savings in associated construction costs.  In the case of the Tyson Road roundabouts, the preliminary engineering determined that roundabouts were the preferred option primarily due to the safety and efficiency aspect for the short-term and long-term.  The preliminary engineering also determined that the initial construction cost would be approximately equal for signals or a modern roundabout.   

How do I find out more about roundabouts?

There is a great "Safer Choice" roundabout video posted on YouTube:

The Region of Waterloo in Ontario has a good presentation available at:

Washington State Department of Transportation website:

How do I drive in a roundabout?

On your approach, slow down and watch for pedestrians. To enter the roundabout, complete visual checks of all vehicles already in the roundabout and those waiting to enter (including cyclists). Traffic in the roundabout has the right-of-way. When preparing to enter the roundabout, pay special attention to the vehicles to your left. Adjust your speed or stop at the yield sign if necessary. Watch for a safe opportunity to enter the roundabout. Enter when there is an adequate gap in the circulating traffic flow. Do not stop except to avoid a collision. To exit the roundabout, be sure to signal your exit and watch for pedestrians. Maintain your position relative to other vehicles.

Are roundabouts appropriate everywhere?

No. The choice of using a roundabout versus a traffic signal is a case-by-case decision. Each candidate intersection should be evaluated individually to determine whether a roundabout or a traffic signal is more appropriate.