It used to be that if you wanted to see a roundabout, you had to take a transatlantic flight to a country like Britain or France, where it seems you can’t drive a mile (or a kilometer) without encountering one.
That’s no longer the case. Since the late 1990s, roundabouts have experienced rapid growth in North America, with an estimated 10,000 of them now spread across the U.S. (and 1,250 in Canada).
What’s driving the change?
In a word: safety. Research has shown that roundabouts and other types of “circular intersections” can dramatically reduce motor vehicle crashes. According to the Federal Highway Administration (FHWA), they can reduce traffic-related injuries and deaths by 78-82% compared to traditional stop- and signal-controlled intersections.
There are other benefits, too. Roundabouts can handle more “throughput,” meaning more vehicles can pass through them, easing congestion and increasing capacity. Plus, they eliminate hardware, maintenance, and utility costs, making them much more affordable than signalized intersections over the long-term.
Are they safer for pedestrians?
It depends on the type of circular intersection, and what kinds of pedestrian infrastructure is in place. While “roundabout” is often used as a blanket term to describe all road features that require traffic to move around a center island, not all circular intersections can be characterized as roundabouts.
- Rotaries are generally large in diameter (sometimes more than 300 ft.) with high speed limits (30 mph+) and multiple lanes. They were popular before the 1960s, and often lack the bicycle- and pedestrian-friendly enhancements seen on more modern roundabouts. [source]
- Neighborhood traffic circles are typically used at the intersection of two local residential streets for the purpose of traffic calming or aesthetic appeal. Occasionally, they include marked crosswalks, but more often than not they are unmarked. [source]
- Modern roundabouts employ specific design features to control speed, efficiently move traffic, and accommodate multimodal transportation (e.g. “splitter islands” that channelize traffic and give pedestrians a safe place to rest mid-crossing). [source]
Although there is virtually no official data to back it up, modern roundabouts are believed to be one of the safest types of intersections for pedestrians. A few reasons:
- Their curved geometry naturally slows approaching traffic, and keeps it slow until they have exited the roundabout (the smaller size of a modern roundabout compared to a rotary keeps speeds in the 15-20 mph range, making it easier for drivers to see and react to pedestrians, and reduces the severity of injury if a crash does occur).
- They generally have shorter crossings and require pedestrians to negotiate only one direction of traffic at a time. Splitter islands allow pedestrians to cross in two phases, pausing to rest in between. This is especially helpful for younger and older pedestrians, as well as those with disabilities.
Safety for all road users
Despite these advantages, concerns have been raised about their safety, especially for pedestrians with vision loss, who rely on audible cues to tell when it’s safe to cross. (In a roundabout, traffic flows in all directions, limiting helpful sound cues).
To alleviate this issue— and enhance roundabout safety and accessibility for vulnerable road users—rectangular rapid-flashing beacons (RRFBs) can be used. Ideally installed at the either end of each crosswalk (as well as on the splitter island), RRFBs facilitate driver recognition and awareness of pedestrians at or near a crosswalk with high-intensity LEDs that flash in an erratic, attention-grabbing pattern.
RRFBs can also be used in conjunction with an audible information device, an MUTCD-compliant push button that provides an audible message (“Yellow lights are flashing”) to pedestrians with vision loss. And additional treatments such as raised crosswalks, high-visibility pavement markings, overhead lighting, and advance warning signage can also be used on their own or in conjunction with RRFBs to improve the safety of all road users.
>> Roundabout RRFBs in Kahului, HI (case study)
>> Roundabout RRFBs in Red Deer, Alberta (case study)
>> Roundabout RRFBs in Edmonds, WA (case study)
>> RRFB Application Guide
>> The FHWA’s Roundabouts Proven Safety Countermeasure PDF