Friday, October 8, 2010

Cyclists and the Safety of Roundabouts

A Winnipeg Sun has come out in support of the mini-traffic circles.

The circles and “bikeways” will almost surely make the city not only better for cycling, and bring a so-called “cleaner and greener” urban landscape, but give a somewhat easier ride to many motorists tired of jostling with bicycle-riders for road space.

“It is going to take a little bit of adjustment at the beginning. But once everything is there, people will see the overall benefit of having these measures that we’ve taken,” says Luis Escobar, the city’s transportation manager.

“The overall purpose of a traffic circle is to make sure motorists aren’t driving too fast for the area. The people walking and cycling will feel a little less intimidated.”

But are they really safer for cyclists?

A number of British studies studies say no.

While cyclists are vulnerable at roundabouts, this is true of most forms of non signal junction control. The use of outward crossfalls on circulating carriageways and relatively narrow lanes on the approaches to mini-roundabouts all help cyclists to be part of the traffic rather than obstructions that "get in the way". For mini-roundabouts in particular, the repeated failure at many sites of drivers to appreciate the presence of the roundabout in the first place put circulating cyclists in great danger - ensure your designs get ALL drivers out of "auto-pilot".

From a German study:

The study found that bicyclists' risk is high in all such intersections, but it is much higher when the junction has a marked bicycle lane or sidepath around its outside...

There is no marked path in the roundabouts on Grosvenor Avenue. However, the curb bump outs force cyclists into the middle of the circle and all studies shown indicate there is danger for the the bikes.

However, do some of the bike advocates seem to care about this?

Residential roundabouts are not uncommon on any old street but are heavily used on bike routes. They very successfully slow down cars and also provide a seamless, quick and safe intersection for bikes to cross. I find they also discourage drivers from using the route since they’re forced to slow down keeping these streets quiet.

So the objective for some is to force cars to go elsewhere?

This bike advocate doesn't seem to realize the studies show that roundabouts are not safer for cyclists. He is of the opinion that it will drive automobiles away.

It is a pretty aggressive stance.

Whoever thought that combining bike paths and traffic roundabouts into one surely did not read the available data on the subject.

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mrchristian said...

Are those studies for the same sized driving circles, though ?

I've spent time and have driven in both Germany and France and those things on Grosvenor would be considered a pimple in the tarmac versus an actual traffic circle bringing together four major roads with major loads and types of traffic.

I could certainly see actual traffic circles being dangerous for cyclists. Getting your car through the outside turning lane into the centre driving lane then back out to the turning lane again with 20 other cars and a few semis to navigate takes a lot of concentration. Toss in a cyclist outside the outside turning lane and I can imagine the results from time to time.

Really, these things are glorified bollards not actual traffic circles. If you cant manage to slide your way around them you probably shouldn't have a drivers license.

John Dobbin said...

@Christian: The British study was for mini-roundabouts specifically.

The German study was for all three sizes of roundabouts.

The U.S. study says that mini-roundabouts are not that great for cyclists and pedestrians.