An article on the UKrant.nl Web site describes an intersection in the Netherlands with simultaneous green lights in all directions for bicyclists. The headline, “How to Survive Simultaneous Greens” misrepresents the installation (not all greens actually are simultaneous) and tends to promote a spirit of support for careless innovation.
The video below appears at the top of the article. The featured still image looks benign enough. When you click on the image to set it into motion you’ll see that bicyclists are crossing at right angles to others, and some are taking odd routes across the intersection.
Alle Richtingen Tegelijk Groen from UKrantvideo on Vimeo.
How to survive simultaneous green lights? Same way we survive any uncontrolled intersection: yield to traffic already in the intersection. Note in the photo that the simultaneous green lights are only for bicyclists, who have special bicycle signals. Motor vehicles are shown waiting for red lights.
There is no legal right turn on red either, so the motorists may not enter the intersection. Bicyclists enter from a narrow channel to the right of the waiting motor vehicles and so the intersection works more or less like a roundabout during the all-green bicycle phase. This treatment solves the problems with right-hook and left-cross conflicts, at the cost of increased delay for everyone because of the additional signal phase.
Couple quotes from the article:
In the subhead; “It might look chaotic, but in fact – it’s the safest way to do things.”
A couple of paragraphs in: “When the city of Rotterdam tried to implement a similar system, there were two accidents in the first two minutes, and the alderman quickly cancelled the experiment.”
If people understand to circulate as in a roundabout, then it is going to be reasonably safe. If not — chaos, of which there is much in the video.
The article mentions two problems in Rotterdam: the intersection was too small, and people weren’t used to it. The article makes no mention of any rules for circulating in this intersection or education in how to use it — essential to improve the survival rate — and I can add, there is no mention either of how pedestrian traffic is addressed. (The video, however, does show pedestrians crossing during the bicycle phase — so the rules for them during the bicycle phase are also the same as in an uncontrolled intersection: cross in any direction at any time, and drivers — bicyclists — must yield) The claims that this is the safest arrangement is unsubstantiated in the article and undercut by the Rotterdam experience.
Here is another video, of a bicycle roundabout on the campus of the University of California, Davis:
I think that a bicycle roundabout is a valid concept where bicycle traffic is heavy enough and motor traffic light enough to justify it. The Davis installation, which prevents chaos by channelizing the bicycle traffic, is better than the Groningen one, where bicyclists — and moped riders, who also use the bikeways — ride straight across from one corner of the intersection to another, and take shortcuts that put them into conflicts. Whether that kind of traffic flow could be achieved without physical barriers, allowing heavier motor traffic between the bicycle-only signal intervals, is another question, though.
I love your simple explanations that points to the matter in seconds makes the reader see through the fog. I sometimes advocate that lowering speed limits in cities would help intersections to be all green. Pointing out that an intersection would transfer to a roundabout to be more smooth is an upgrade but space of intersection could be an issue, especially with cars.
If the intersection could operate as a roundabout during the bicycle phase only, that would not require more space. The problem is that there could be no physical barrier as with the Davis roundabout because the intersection also has to operate as a crossroads for motor vehicles. Most cyclists in the Dutch intersection are operating as if the intersection were four crossroads intersections, one at each corner where bicyclists traveling through cross the path of those entering. They are operating according to the standard rule for an uncontrolled intersection: yield to traffic coming from the right. It’s tricky because the traffic is too heavy and fast for that to work smoothly, as the video shows. Bicyclists turning left and making U turns, however, are taking some odd and unconventional routes which lead to further confusion. Maybe there is some clever treatment which would make the intersection work well as a roundabout for bicyclists and a crossroads for motorists, but one doesn’t pop into my mind.