Reduction in number and severity of crashes
Source: FHWA and IIHS
Several features of the modern roundabout promote safety. The safety benefits alone should be enough to convince roundabouts are a great idea. According to a study by the Institute for Highway Safety of locations where stop signs or traffic lights were replaced by roundabouts, all crashes were reduced by 37 percent and serious crashes fell by 75 percent, including a 90 percent reduction in fatalities. This means not only fewer crashes, but also most will be able to walk away from them.
At traditional intersections, some of the most common types of crashes are right-angle, left-turn, and head-on collisions. These types of collisions can be severe because vehicles may be traveling through the intersection at high speeds to "beat the red light." With roundabouts, these types of potentially serious crashes essentially are eliminated because vehicles travel in the same direction.
Installing roundabouts in place of traffic signals can also reduce the likelihood of rear-end crashes by reducing abrupt stops at red lights. The vehicle-to-vehicle conflicts that occur at roundabouts generally involve a vehicle merging into the circular roadway, with both vehicles traveling at low speeds – generally less than 25 mph in urban areas.
A traditional intersection has 32 potential conflict points A roundabout has only 8 potential conflict points (roundabout conflict image).
Pedestrians need only cross one direction of traffic at a time at each approach as they traverse roundabouts, as compared with unsignalized intersections. In addition, crossing distances are relatively short, and traffic speeds are lower than at traditional intersections. The conflict locations between vehicles and pedestrians are reduced from 16 to 8 since conflicting vehicles come from a more defined path at roundabouts. In addition, the speeds of motorists entering and exiting a roundabout are reduced with good design.