Very carefully, especially if they are two lane, first intersection after motor vehicles come off a high-speed road, or not well designed.
Originally Posted by buffalo_cody
What is well or not well designed? Several studies suggest that some roundabout types can increase injury and fatality rates for bicyclists. The riskier roundabouts tended to be ones in built-up areas that replaced intersections and ones with multiple lanes.
Smaller diameter single lane mini-roundabouts may be safer for cyclists. One study in the UK found that signalized roundabouts were probably better. Some features that may increase cyclist safety at roundabouts are:
arms that are perpendicular, rather than tangential to the roundaboutA well illustrated presentation on cycling through roundabouts is Bicyclists at Roundabouts: State of the Practice LINK. This may be helpful as the last paper below comments "... Underestimation of risk and lack of knowledge about relevant traffic rules may contribute to car–bicycle collisions in roundabouts. Cyclists prefer road designs with a clear regulation of road user behaviour. A need to increase knowledge about traffic rules regulating road user behaviour in roundabouts is identified."
single lane entries and exits (widths 4-5m).
minimal flare on entry
inscribed circle diameter 25-35m
circulatory carriageway 5-7m
Some studies for those who want to read more:
Bicycle and Pedestrian Considerations at Roundabouts, Florida Department of Transportation
Summary of Final Report, WPI# 0510824 September 2000
Safety effects of roundabouts in Flanders: signal type, speed limits and vulnerable road users.
Accid Anal Prev. 2007 May;39(3):591-9. Epub 2006 Nov 21.
The effect of roundabout design features on cyclist accident rate
Accident Analysis & Prevention, Volume 39, Issue 2, March 2007, Pages 300-307
The effects of roundabouts on traffic safety for bicyclists: An observational study
Accident Analysis & Prevention, In Press, Corrected Proof,
Abstract (in press) LINK
Car Drivers' Adjustments to Cyclists at Roundabouts. "The most frequent bicycle accident type at roundabouts has been shown to be between the entering driver and the circulating cyclist. ..."
Cyclists’ perception of risk in roundabouts. "Converting an intersection into a roundabout improves motor vehicle safety, but a similar safety effect is not found for car–bicycle collisions"
Accident Analysis & Prevention Volume 40, Issue 3, May 2008, Pages 1055-1062. LINK