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A bicycle friendly roundabout: Designing to direct cyclists to ride where drivers look.

Cumming, B (Peer reviewed)

Cycling

ACRS conference 2011

Installing a roundabout typically improves road safety by reducing speeds and by reducing the number and severity of conflict points. This paper examines why roundabout safety benefits don’t extend to cyclists and how roundabouts might be changed to reduce roundabout crashes involving cyclists.

Conflict points and “conflict paths” are considered. A comparison is made between cycling in the centre of the lane (along the primary conflict path) versus cycling along the left edge of the lane. If on the edge, a second conflict path is created, which may easily be overlooked in a one-lane environment.

The literature review confirms that many researchers have concluded that the outer edge of roundabouts is a dangerous place to ride, and notes various strategies which aim to get cyclists to ride in the centre of lanes when approaching and negotiating roundabouts.

All roundabout crashes occurring at Victorian roundabouts from 2005-2009 are assessed, with DCAs recategorised into roundabout crash types. The most common crash is “entering-circulating”, accounting for 48% of all crashes. For crashes involving bicycles, they account for 82%, while no other crash type accounts for more than 4%. An entering car striking a circulating cyclist accounts for nearly a quarter of all roundabout crashes in Victoria.

Austroads and VicRoads design guidelines promote use of bicycle lanes through roundabouts. They appear to overlook both the published safety research and their own conceptual advice.

Cyclists are most likely to be seen if they ride in the middle of the driving lane. This maximises visibility to cars, maintains a simple one-lane conflict point environment, and reduces the likely speed of impact if a collision does occur.

The “C1 Roundabout” is a new bicycle friendly design which provides clear cues to cyclists to move out from the kerb to the middle of the lane – to facilitate cyclist positioning along the “conflict path” where drivers are most likely to look. If cyclists are more likely to be seen, they are less likely to be crashed into.

Treatments are proposed which slow approaching, entering and circulating vehicles and align entering vehicles for improved visibility to the right. It is recommended that road authorities review the research about the dangers for bicycles in the outside edge of roundabouts and revise design guidelines, with circulating bicycle lanes prohibited rather than recommended.