City of Avondale Estates Intersection Improvement/Roundabout and Road Diet Feasibility Study

ROUNDABOUT INTERSECTIONS

How do roundabouts work? A roundabout is a form of circular intersection in which traffi c moves around a central island in a Entering Traffi c KEY ROUNDABOUT Entering traffi c in a rounadbout yields to traffi c COMPONENTS counterclockwise direction (or moving to the right as already in the circle. This allows the roundabout you enter). Traffi c entering the circle must yield to traffi c to constantly process traffi c; even if traffi c on Approach roadway one approach yields and waits, the roundabout Splitter Island already in the circle. The entering roadway is diverted is allowing traffi c from other approaches to Circulating Roadway enter. Apron to slow down traffi c, and it may enter the circle without Roundabouts can be applied to compled intersections, but Central Circle they typically require a larger footprint to function. stopping if there is not already traffi c in the circle to Pedestrian Crossings which it will yield.

PPedestrianedestrian crossingscrossings areare mademade safersafer bbyy mmovingoving tthroughhrough tthehe Traffi c only moves in one direction. Motorists making a ssplitterplitter island,island, wherewhere additionaladditional signagesignage raisesraises motorists’motorists’ right turn travel one quarter of the circle, and motorists aattention.ttention. making a left turn travel three quarters of the circle. Are there places where roundabouts don’t work? The Circulating Roadway Because roundabouts require entering traffi c to yield to There are two main components to the traffi c in the circle, there are conditions in traffi c fl ow circulating roadway: the driving space itself, typically wider than traditional and balance of traffi c between two crossing streets traffi c lanes to allow for the turning Pedestrians and Bicycles where roundabouts work well and process traffi c more radius of larger vehicles, and an apron Pedestrians cross each of the divided approach that is fl ush with the roadway but roadways and typically have a place in the splitter effi ciently than a traffi c signal. By the same token, there textured (with rumble strips or other island to take refuge. This shortens crossing distances paver materials) to slow vehicles over moving vehicle paths (to only one direction at a are other conditions where they do not—traffi c may be down further. This allows drivers not time) and gives pedestrians another opportunity to imbalanced and not easily allow entering traffi c from used to navigating turns to keep from look for oncoming traffi c. hitting raised curbs or other vertical one or more roadways to enter the circle safely and elements. Bicycles use the roundabout circle along with effi ciently. vehicles. As the design of the roundabout is intended to slow vehicles, this allows bicycles to safely take BBicyclesicycles movemove throughthrough thethe circulatingcirculating roadwayroadway ooff the center of the circle and leave the roundabout rroundaboutsoundabouts alongalong withwith vehicles.vehicles. without danger of a vehicle crossing their path. What is the typical size of a roundabout? ROUNDABOUTS AND SAFETY This depends on several factors, including the amount of traffi c the roundabout is designed to handle, the space into which it must fi t, and the speeds of surrounding roadways.

Conflicts unique to bicycles Bicycle Routes Typical one-lane roundabouts (with one lane in the Converging Crossing Diverging Conflicts in common with Motor Vehicle Routes Crossing motor vehicles circulating roadway) are anywhere from 100 to 125 feet Converging Conflicts unique to bicycles Diverging Crossing Conflicts in common with motor vehicles across. Two-lane roundabouts are often larger than this, For Motorists For Pedestrians For Bicycles generally up to 150 feet. A typical intersection has up to 24 points of potential confl ict, For pedestrians, typical intersections have up to 16 points of Because cyclists typically ride on streets to the right of moving many of them related to crossing vehicle paths. Roundabouts potential confl ict where vehicles may cross pedestrian paths. vehicles, they face a unique set of potential confl ict points reduce this number to eight points, related to the weaving These confl icts become more complex on intersections in a typical intersection. Roundabouts reduce the number of of traffi c entering and exiting the roundabout with the traffi c of multi-lane roadways. Roundabouts reduce this number points of potential confl ict from 24 to eight, with all related already on the circle. of confl icts to eight points, and pedestrians have a refuge to bicycles merging with traffi c entering and exiting the circle between each of them. (which roundabout speeds can help to mitigate).