Sunday, 13 March 2016

Roundabouts. Priority for cyclists or not?

One of the most contentious debates in the Netherlands about cycling aside from mopeds are roundabouts in the built up area with priority for cyclists or not (I can't think of any examples where people are complaining about the lack of priority in the rural area). I will try to make a case for they type I support. Note that this supersedes the "New standard intersection" I proposed for Edmonton about half a year ago. The Aviewfromthecycleapath blog goes in detail about this:

The design I support is that of the non priority design. It sounds like I don't really endorse cyclists now do I? In a perfect world where cars are always going to yield to you, then yes the priority design would be likely better. But we don't live in one of those worlds. There are several components to the factors that made me end up supporting the non priority design.

Drivers often made mistakes while cycling, and while cyclists do them too, on the non priority design, the drivers are the ones who can make the errors. You are not dependent upon them for your own safety. And even if you do ride assuming you have priority, the slow speed of cars means that crashes are less likely overall and less likely to be as injurious, and the angles and the relatively slow speed required by all road users at the point of crossing (cyclists with sharp corner radii, cars also with sharp corner radii, narrow lanes, having to go around a median refuge and potentially a speed table) means that everyone has time to react.

Pedestrians, as they are slower, are able to get priority with zebra striped crossings, especially if combined with a raised table that motor vehicles have to cross. When there are too many pedestrians, enough that they can get in the way to the orderly movement of cyclists, then they do need a separate sidewalk. This isn't really a problem though. You can even built zebra crossings over the cycle path if pedestrians have challenges crossing.

It is not as problematic as people might think. Even when crossing James Mowatt Trail at Bowen Wynd, even after a heavy flow from one direction, I can still often find gaps. If the traffic was going slower, at 50 km/h, they could not turn right where I was crossing and I had a median refuge (and hopefully things to ensure that the drivers do go at 50 km/h, although at roundabouts at that point it is likely less, probably between 30 and 40 km/h), it would be even easier to cross. Also note that on cycle priority roundabouts, on entry, you do have to yield to cyclists on the roundabout, and in many cities that can be more of a challenge than cars just due to the high volumes of cyclists. You also have to be fairly slow on the entry, even for a right turn, about 15-20 km/h, rather than the 25-45 km/h that non priority roundabouts often allows when bypassing the roundabout. You also only slow down, when when you cross motor vehicles, exactly where you need to yield. This coincides with the requirement that yielding is something that you naturally want to do by road design. It's up to you to believe what you want, but I believe that a crash is very inconvenient.

And compare this with the alternatives. Even with 2 green phases for each cycle for cyclists and pedestrians, it can still be a wait, perhaps 30 seconds. You can usually turn right without stopping on a non priority roundabout anyway, often without even slowing down, so this doesn't affect the average wait delay. You often only wait perhaps 10 seconds at most on non priority roundabouts, almost always much less, and often even without stopping, just regulating your speed. This is due to the slow speeds of everyone involved and good sightlines. With only a single lane at a time to deal with, it is very easy to use.

This is quite safe as statistics show. Despite heavy use, for all of the collision statistics that I know of between 2007 and 2012, only 1 at all of Assen's single lane roundabouts combined that resulted in an injury for cyclists, and there was just one more small crash between cyclists and motor vehicles, only ~ 25 motor vehicle-motor vehicle crashes on the single lane roundabouts, 1 injury, and no pedestrians in a crash to begin with. Over 5 years, so an average of 5 motor vehicle crashes per year, an average of .2 crashes per year involving injury to cyclists, and the same rate for motor vehicles. This is including quite a lot of children, and a lot of cyclists who are inebriated and who don't have their lights on at night, lots of people who are distracted in some way. I'd consider it quite a good design also by this measure. And note that this design accounts for the fact that most drivers aren't used to cyclists here. In the Netherlands cyclists are everywhere, and you grew up being one and being around them, including in your parent's car for most children and you learned to drive with all of these cyclists around you. Our drivers haven't done that. So the priority roundabout is even more risky.

This design accounts for the 5th principle of Sustainable Safety too. That you must be able to know what you are capable of doing in traffic and know what other people are capable of doing too. With the priority design, there is a lot of head swiveling for everyone. Not very good.

You often get to avoid roundabouts like this altogether, or at least minimize your interaction with them. While you could cycle next to James Mowatt Trail, you could instead be cycling in the middle of Rutherford away from motor traffic, and if all the crossroads on James Mowatt were changed to roundabouts, you could avoid them completely. By providing bidirectional cycle paths around most roundabouts (this is not about the cycle paths on the approach, but the ones that link the cycle paths that do link the approaches), you have a choice in which direction you want to go in. Right turns and going straight past 3 way roundabouts are often possible.

This won't always work though. If you are crossing an arm that has more than 1500 PCU/h on it, then it will be a challenge to get through. Traffic lights become an option, and grade separation is another option for minimizing your interaction. But this still means that there is a very high capacity. The roundabout itself can often handle between 20k-25k vehicles per day, as can each of the approach arms, and most arterial and to my knowledge, all, collector roads are sufficiently low volume to handle this. James Mowatt, even on the section that was recently widened, was that volume. 17 Ave and James Mowatt is under that limit and yet it has traffic lights. Many places in the city meet that limit. 40 Ave and 106 St is another good example of where one of these roundabouts would be an excellent option. Above 1500 PCU/h, grade separation for the cyclists, if used, is an option, but this is limited to about 1750 PCU/h on the arms, for about 36000 PCU/d.

Turbo roundabouts can be used when there is a mismatch in the volume of the arms, when a particular turning movement needs to have extra capacity or when connecting higher speed roads, but this requires grade separation for cyclists, mopeds and pedestrians, however this is cheaper and eaiser to use than you think.

Here are some other benefits of this design. It avoids traffic signals, that are often the source of much fustration and and increases the risk of dangerous collisions. And as many of Assen's roundabouts prove, a dramatic drop in the less dangerous crashes like fender benders as well, many have perfect safety records. It is greener, as there is less delay for motor vehicles too, less smog. Less space is needed to be used for motor vehicles. You can use things like extra trees and plants for the rest of the space. And because this design makes cycling easy and convenient, and also still quite fast despite the need to yield to motor vehicles if you cross their paths, That encourages more cycling, and combined with a dense network of high quality cycle paths without barriers and with very little need of stopping or slowing, omafietsen in every (bike) store and parking for bikes everywhere, it makes that the rate of cycling would be far higher. This reduces the number of motor vehicles even more, and makes it easier to cross a non priority design. A positive feedback loop.

All of this makes cycling quite nice and convenient. And it keeps everyone safer, pedestrians and motorists included as a side effect. It is cost effective, about as costly as a traffic light controlled crossing if retrofitted and almost no extra costs if being added from scratch, especially given the savings from not needing traffic lights. A simple, elegant solution. It is time to adopt it.

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