Roundabouts: Why They Are Dangerous for Cyclists and What Can Be Done about It

Roundabouts experience fewer and less severe vehicle crashes than typical intersections. Yet this safety benefit does not extend to bicycles. The reasons for this are analysed through a literature review and a case study of roundabout crashes occurring in Victoria from 2005-2009. The most common type of roundabout crash is 'entering-circulating' vehicle conflicts (82% for roundabout crashes involving bicycles). Speed and visibility of circulating vehicles are the major contributing factors particularly as bicycles are often located where drivers do not look. Austroads promotes the use of circulating bicycle lanes. However, this analysis explains why such designs may increase risks to cyclists. Many researchers have found that riding on the outside edge of circulating carriageways is dangerous for cyclists. Little has been written about why. Many cyclists ride close to the kerb, with cars beside them 'sharing' the lane, effectively allowing two traffic streams within one lane. At a 1-lane roundabout, this creates an environment with 24 conflict points, but approaching drivers expect just 4. Drivers check the inner path for a gap, ignoring the unexpected outer path and sometimes striking a cyclist they never saw. Cyclists are safest if they merge with cars before a roundabout then ride in the middle of the driving lane. This maximises their visibility to cars, maintains a simple one-lane conflict point environment, and reduces the likely speed of impact if a collision does occur. Treatments are proposed which slow approaching, entering and circulating vehicles and facilitate central lane positioning by cyclists for maximum visibility.