Modern roundabouts by their design require motorists to slow down typically to less than 25 mph, and preferably 15 mph to proceed through the intersection. The literature shows that, given a properly designed single-lane roundabout, motorist and pedestrian safety is almost always improved when compared to conventional intersections. Results regarding cyclist safety are somewhat mixed. Roundabouts have fewer conflict points and lower speeds compared to conventional intersections, resulting in a significant overall reduction in the severity of crashes for all users, although the frequency of some crashes may increase. Multi-lane roundabouts present some challenges to pedestrians, thus reducing the safety effects that roundabouts provide.
As with conventional intersections, a cyclist using a roundabout can proceed either as a motor vehicle or as a pedestrian using the sidewalk and marked crosswalks. If proceeding as a motor vehicle, merging with traffic is required at the entry. This may take some skill and judgment but is not unlike traveling through a conventional intersection. Motorists must detect cyclists upon entry, circulating and exiting so as not to merge into or turn in front of them. As with complex intersections with multiple turn lanes, a multi-lane roundabout also becomes more difficult for cyclists to traverse.
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This figure is a diagram of a roundabout with four two-lane roads (one lane each way separated by an island) approaching it: one each from the top, bottom, left, and right and single entering and exiting lanes on all legs. It has the caption "Tips for safely walking and biking through a roundabout."
The diagram has a set of purple arrows illustrating a path for how pedestrians can safely walk around the roundabout to get from the northeast corner of the intersection to the southwest corner. The path starts at the east end of the crosswalk across the north leg, passes to the splitter island dividing the north leg's exit and entry (where an icon of a pedestrian is shown), and then passes to the west end of the crossing across the north leg. The path then curves along a sidewalk that is separated from the roundabout curb by a green landscaping buffer until it reaches the crosswalk across the west leg. The path then proceeds to the splitter island in the west leg and then to the south end of the crosswalk. The path has the caption "Walk around the outside; don't cross through the middle."
The figure also depicts two paths for cyclists. One set of red dotted lines depicts the safe path for a cyclist riding his/her bike by using the travel lane as a vehicle. This is shown as a path starting from the south leg. The path enters the roundabout and then splits into two paths, with one depicting a through movement to the north and one depicting a right turn to the east (all in travel lanes). The second set of red dotted lines depicts a cyclist walking his/her bike along the sidewalk. This is shown as a path starting from the sidewalk on the east side of the south leg. The path proceeds north along the sidewalk and curves along the perimeter of the roundabout to the south side of the east leg. At the crosswalk on the east leg, the path splits into two, with one using the crosswalk across the east leg and one continuing to follow the sidewalk to the east. The caption reads "Ride your bike as a vehicle or walk your bike as a pedestrian."