Modern Roundabouts: Frequently Asked Questions
A number of alternatives were considered to deal with the noted issues. Options included:
- What is a roundabout?
- How does a roundabout work?
- Are there any roundabouts in Ontario?
- What is the difference between a roundabout and a "traffic circle"?
- How do roundabouts affect traffic flow?
- How do roundabouts affect safety?
- Are roundabouts safe for pedestrians?
- Are roundabouts safe for the visually impaired?
- Are roundabouts safe for cyclists?
- Can older drivers adjust to roundabouts?
- Can a roundabout accommodate large trucks and farm equipment?
- Is snow removal an issue at roundabouts?
- What about emergency vehicles?
- When and where is a roundabout appropriate?
- Do roundabouts require more space than a traditional intersection?
- Is the cost of constructing a roundabout more than a traditional intersection?
- How do I drive through a roundabout?
- Are there special lighting requirements for roundabouts?
A roundabout is an alternative form of intersection traffic control. A modern roundabout is a circular intersection with yield at entry. It promotes safe and efficient traffic flow. They were introduced in the U.K., but are gaining more widespread use in North America, with implementation in many U.S. states and several Canadian provinces. Typical characteristics of a modern roundabout include:
- Yield at Entry
- One-Way Travel around the central island (counterclockwise)
- Slower Speeds
Roundabouts have the potential to reduce collisions, traffic delays and fuel consumption resulting in improved air quality through reduced vehicle emissions.
In Ontario, vehicles travel counterclockwise around a central island. Traffic entering the roundabout must yield to circulating traffic. Curves on the approaches to roundabouts require all vehicles to slow down before entering. Designs ensure that slow speeds are maintained around and at exits to the roundabout. Drivers approaching a roundabout must reduce their speeds, look for potential conflicts with vehicles already in the roundabout, and be prepared to stop. Once in the roundabout, drivers should not need to stop and can proceed to their exit.
In Ontario, a number of municipalities (such as the Region of Waterloo, City of Ottawa and the City of Hamilton) have constructed roundabouts on municipal roads with great success. However, this is a relatively new method of traffic control at intersections on provincial highways. Roundabouts have been successfully implemented on provincial highways in other Canadian provinces.
Modern roundabouts are generally much smaller than older traffic circles, and require vehicles to negotiate a sharper curve to enter. These differences make travel speeds in roundabouts much slower than speeds in traffic circles. Because of the higher speeds in traffic circles, many were equipped with traffic signals or stop signs to help reduce potential collisions. In addition, some traffic circles operated according to the traditional “yield-to-the-right” rule, with circulating traffic yielding to entering traffic.
Because approaching traffic only has to yield to vehicles already circulating in a roundabout, movement is often without delay. It has been shown that a roundabout can move traffic through an intersection at a much higher rate than traditional intersection controls.
Several features of roundabouts promote safety, primarily lower operating speeds, one-way traffic circulation and a reduced number of conflict points. At traditional four-leg intersections with stop signs or traffic signals, there are a total of 32 potential collision points. The most common types of crashes include rear-end, right-angle, left-turn, and head-on collisions. These types of collisions can potentially have severe impacts since vehicles may be traveling through the intersection at high speeds. With roundabouts, these potentially serious collisions are essentially eliminated because vehicles travel in the same direction at a reduced speed. The elimination of traffic signals removes any incentive for drivers to speed up as they approach green lights, or to stop abruptly at red lights.
In contrast, there are only 8 points of conflict in a roundabout. Typically, vehicle-to-vehicle conflicts in a roundabout are related to vehicles merging into the circular roadway, however both vehicles would be traveling at low speeds. The most common types of conflicts in a roundabout are, rear-end, sideswipe and entering-circulating. Proper design can help to optimize the safety benefits of roundabouts.
Roundabouts are generally safer for pedestrians than traditional intersections. If it is necessary for pedestrians to cross the roadway, they cross 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, as in the case at Highway 33, have been reported to involve substantially lower pedestrian crash rates than comparable intersections with traffic signals.
When walking through a roundabout, pedestrians are encouraged to cross at the appropriate place, where the curb is lowered and to use the ”splitter islands” as resting points. Watch for gaps in the traffic and choose a safe time to cross. Pedestrians should not cross to the central island of the roundabout.
People who are visually impaired may experience difficulty using roundabout crosswalks, particularly where traffic volumes are high. Roundabouts, like channelized turn lanes, present challenges different from other intersections since the traffic is most often under yield control as opposed to stop control. It is difficult to be sure that traffic will yield to pedestrians, and the continuous circulation of vehicles makes it difficult for the visually impaired to determine significant gaps in traffic movements. In addition to determining when to cross the road, pedestrians with vision impairment must identify where to cross, which way to walk during the crossing, and when they have arrived at their destination curb or island.
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.
Relative to other age groups, senior drivers appear to be over-involved in crashes occurring at traditional intersections. Roundabouts eliminate a number of problem areas for older drivers that are typical of traditional intersections, such as left turns and entering busy thoroughfares from cross streets.
Yes. With proper design, roundabouts can accommodate the turns and movements of larger vehicles, such as trucks, buses, farm equipment and other large vehicles. A main design feature is a truck apron which provides an area between the circulatory roadway and the central island, over which the rear wheels of these vehicles can safely track. A truck apron is used rather than increasing the normal lane width, which might encourage smaller vehicles to move at higher speeds through the roundabout. Typically, the truck apron is composed of a different material and/or texture than the paved surface, to discourage routine use by smaller vehicles.
A number of communities in snowy areas have installed roundabouts, including Hamilton, Kemptville, Waterloo, and Ottawa in Ontario, along with various locations in the U.S. All indications are that while there is an adjustment period for snowplow crews, there are generally no major problems with snow removal in roundabouts. Roundabouts actually make it easier to turn snowplows.
New York State DOT has a video on its website that shows a plow operator clearing a roundabout.
Modern roundabouts are designed to accommodate emergency and other large vehicles. Other vehicles should pull over as far to the right as possible and let the emergency vehicle pass after exiting as soon as possible. Whenever possible, other vehicles should completely clear the roundabout and pull off to the side.For more information go to Driver's Handbook, section2.6.8.
Roundabouts are appropriate for many intersections, including locations experiencing high numbers of collisons, long traffic delays, four or more approaches with relatively balanced traffic flows, and frequent left turn movements. They are an appropriate solution in both urban and rural settings, along busy arterial roadways, as well as at certain highway entrances and exits.
Roundabouts can process traffic more efficiently than traffic signals and stop signs; therefore, typically requiring fewer traffic lanes to accommodate the same volume of traffic. Roundabouts do not necessarily require more space than traditional intersections; however, geometric design details vary from site to site and must take into account traffic volumes, land use topography, and other significant factors.
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.
Download a .pdf printable version of our safety brochure on how to use roundabouts, featuring tips on how to drive, walk, and cycle safely in roundabouts.
MTO’s Driver Handbook recommends the following:
On your approach, slow down and watch for pedestrians. Stay in the most appropriate lane. 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. Don’t enter directly beside another vehicle already in the roundabout, as that vehicle may be exiting at the next exit. Once in the roundabout, always keep to the right of the central island and travel in a Counterclockwise direction. Do not stop except to avoid a collision. You have the right-of-way over entering traffic. Always signal lane changes. To exit the roundabout, be sure to signal your exit and watch for pedestrians. Maintain your position relative to other vehicles.
Guidance features like signs, pavement markings, and other physical elements (like splitter islands) require adequate nighttime illumination to avoid driver confusion and to increase pedestrian safety.