Sunday, 8 November 2015

Comparison of various intersection design types. Part one: Copenhagen

Anyone who has been doing their research into cycle friendly intersections knows about Copenhagen. With about 25% of the population cycling, that is a pretty impressive number. They also have probably seen this video.

Let's see what intersection design they tend to associate with Copenhagen.
You can click on it for more detail.

Lets go over it piece by piece shall we?

First, we have a right turn lane on all approaches, a curb protected cycle lane on each of the approaches, in and out, a two stage waiting area for cyclists, a bike box (advance stop line) on each approach, and sidewalks on both sides of each approach lane. The cycling area is painted green.

The lane configuration and angles varies from intersection to intersection, but the concept is very similar.

There are more than a few problems. Where should I begin? How about the approach cycleways? They are not well protected, and it would feel not that different than a painted line. It is also not that wide, often 1.5-2.2 metres standard width. It is OK for corridors genuinely constrained, but not as a standard (but the minimum is 2 metres, not 1.5 metres). The fact that you are using paint for the colour is also not good. Even thermoplastic doesn't last all that long. A good asphalt surface can last for a couple decades or more. That includes dyed asphalt.

The fact that you have the dedicated right turn lane on the approaches in the position they are leads to conflicts. That being the conflict that cyclists cross the turning lane at a shallow angle, which is not good for visibility. It is also likely to be relatively high volume, and there is nothing to slow cars down as they approach and make that lane change.

The bike box is not always present, but if it is, it leads to positioning cyclists in front of cars, which car drivers hate on a fast and busy arterial road. Given that it could only help effectively when the traffic light is red, its use it limited. And it is a form of dual networking. A way to turn for confident cyclists, not the ones seeking a safe way to turn left.

The two stage turn can be a good idea, but only if it is protected in the way that a protected intersection would make it, and you have to have short waiting times. In this example, you are positioning yourself right in front of motor traffic. It is also hard to make this turn in this configuration if you are on a big, not nimble or heavy bicycle, something you might have if you are getting groceries or picking up toddlers from preschool. You have no protection from say a driver who is about to run a red light from the cross street.

You are also not able to make a right on red at this intersection (also applies to the top of T intersections), unless you have a specific exemption from the signage, and even if you did, you would have to stop before turning, and you have no protection as you make that right turn. And you would have to do it in the right turn lane, which is shared by automobile traffic, possibly including large trucks.

How are these intersections in general signaled? Usually, it is a bicycle pre green, or advance green, to let those cycling go ahead a few seconds before cars start to move, usually between 2-12 seconds. This is to clear the cycle lanes, let those using the bike box if present make their turn and to clear those who are making a two stage turn go. Then the cars from one street and the bicycles get to go, including left and right turns. And this applies for the cross street too, just rotated 90 degrees or so.

This would be a big improvement over what we have now, and would be capable at least in theory of attaining around 20-25% of people on bike, maybe a little more, a little less, but it is not the best intersection you can get with traffic lights, and why stop at improvement?. You have two other options that are both better than the Copenhagen junction when you have at grade crossings with arterial roads with traffic lights. Simultaneous green and the protected intersection. But this is usually promoted as the way to accommodate cyclists, to coin a phrase (sarcasm). The Complete Streets manual also recommends this sort of Copenhagen style intersection. Let's finally move past this idea, please?

Now you can go see part two: Protected intersections

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