Roundabouts reduce severe and fatal crashes but have more accidents

Roundabout dynamics

[Forum] Tim Bard is quite correct that a roundabout reduces severe and fatal crashes, as compared to a light-controlled intersection (Forum, edition 228), although he does not point out that a roundabout increases crashes overall, because it raises the number of sideswipe contacts that result only in body damage to vehicles, without injury to occupants.

However, a properly designed one-lane roundabout requires an inscribed circle of about 45 metres that would be difficult to achieve at the Rawson/Ocean Beach intersection that we are specifically concerned with.

If a left-turn lane had to be added, the space required would be increased.
The proportion of turning movements, particularly right-hand turns, greatly affects roundabout performance, but without access to the traffic-count figures presumably taken in a proper study of the intersection, it is impossible to say whether traffic lights would improve or detract from the intersection performance.

In most cases, delay times are about the same for roundabouts and light-controlled intersections in suburban areas.
Of course, the typical short sightedness of Council in allowing traffic generating activities to occupy the intersection corners, without any provision for future correction, greatly reduces the possibility of worthwhile improvement, except at significant cost.
The fact that vehicles enter and exit these sites virtually at the roundabout entrance means that there will always be interference with efficient traffic flow.

This will, no doubt, be exacerbated by the proposed redevelopment of the BP site, about which the Council seems to be worryingly sanguine.
Unless Council can, at least, introduce turning slots at the corners, it seems highly doubtful that installing expensive traffic lights will bring about any notable improvement in ease of movement through the intersection.
Given that the Picnic Ave roundabout is costing untold millions, one shudders to think of the cost of traffic lights at this location.

Email, Feb 13
Bruce Hyland, Woy Woy