Monday, January 16, 2012

Bow Roundabout - Again

The Grumpy Cyclist points out that TfL's description of its Bow Roundabout redesign doesn't quite match the video they've produced to illustrate the idea (above). They talk of an 'early start' green phase for cyclists, but the video shows that motor vehicles and cyclists set off at the same time - and in addition there is a separate cycle-control light that goes red, stopping cyclists who are not already in the advance stop box from proceeding into it when motor traffic has green. Grumpy Cyclist also suggests that this is no different to a normal advance stop box. In a sense it is different because there is a separate set of lights before the advance stop box, meaning that crossing the stop line would feel rather more like busting a red light than it usually does (although legally there's not much difference, and as I'll point out later, not much difference in the way the box fills up with motors). The fact that the first and second sets of lights turn green at the same time is not in itself important as time and distance boil down to the same thing: what matters is whether the last cyclist can get past the A12 exit before the first motor vehicle tries to make a left turn across them. Will TfL allow a sufficient combination of time and distance to make sure that happens. If they do, then in theory, there should be no left-hooks, because cycles will either be in the advance stop box safely in front of the motor traffic when the lights go green, or they'll be held at the red cycle-control light, and therefore will never be in the dangerous position of being alongside left-turning motor traffic.

In practice, there are a couple of reasons why this won't work, and one compelling argument that it is cynical and disingenuous to suggest it increases cyclist safety.

It won't work because at busy times, motors will continue past the first amber light and be held in the advance stop box at the second light which will be red by the time they reach it. This will mean there are left-turning motors in the advance stop-box alongside cycles, so when the signals turn green, we'll have exactly the situation we have at the moment, only worse because cyclists have already been forced to the left side. With motors in the advance stop box, there will be limited space for cycles, so they will tend to queue if there are enough of them. This will be intensely frustrating and will tend to encourage cyclists to avoid the controls. They could do this legally by walking across the stop line at the cycle-control light, or illegally by riding across it. Some cyclists will simply take the general traffic lane on the basis that it's quicker and safer than the alternative - you can't be left-hooked if you take the left-hand general-traffic lane.
At quieter times, imagine the following scenario: a slow cyclist arrives at the cycle-control light just before it changes, and proceeds into the advance stop box. Meanwhile, an HGV arrives at the first lights just as they change to green, still rolling at about 30MPH. The HGV catches the cyclist but doesn't see him, and makes the left turn, getting both of them into the next day's Evening Standard.

Why is it cynical? We've got to the point where TfL have been forced to take action because there is an increasing number of cyclists and too many deaths caused largely by dangerous driving. Rather than increase safety while preserving the speed and convenience of cycling (remember they're supposed to be encouraging cycling as a transport mode), they've come up with a solution that means cyclists have two sets of lights to go through, thus slowing their journeys. Motor traffic, by contrast, is only minimally affected, because although it has two sets of lights to get through, they are synchronized so there's only one stop necessary. And if cyclists react to this increased delay by jumping the cycle-control light or taking the main traffic lane, TfL can sneer and throw their hands up, saying that cyclists are just ignoring the safety scheme, and no doubt a judge would find contributory negligence in the case of a cyclist involved in a collision. In effect, this scheme is likely to end up criminalizing cyclists. It is hardly, in Boris's aide Kulveer Ranger's words, "a step change in the way engineers think when planning road layouts". It's the same old car-centric crap we've had for decades. Of course, a small delay would be a reasonable trade-off for safety if it were not for the fact that reasonable tradeoffs between cyclist safety and motor traffic journey speed almost never get made. Iinstead, along entire routes cyclists are continually forced into the same dilemma: either accept delays whose root cause is too many motor vehicles monopolizing the available roadspace, or take risks, and more often than not, it's a case of choosing which risk is the least. At most junctions, the road is designed to stack motor traffic and there's no space set aside for cyclists. You could wait at the back of the queue; in which case you'll have impatient motorists trying to pass you when the lights change. Or you could try to filter to the front of the queue so you're more visible and get away first: in that case you risk not making it to the front before the lights change. Filter on the left and you'll be in a blind spot squeezed between the kerb and vehicles. Filter on the right and you're at risk from oncoming traffic.

So, anyway, I digress. How to fix the Bow Roundabout design? To stop the advance stop box filling up with motor vehicles, there will need to be an 'advance red' phase at the first set of general-traffic signals. That will go red first, and the second signal will stay green for as long as is necessary for traffic already in the advance-stop box to drain out of it (under normal conditions). I don't think that will actually affect traffic flow compared to the scenario where all drivers correctly anticipate the lights. Or do TfL model assuming that vehicles ignore advance stop boxes?

Next, there's the problem of how to eliminate left-hooks during the green phase. That's impossible to do if you have cyclists on the left going straight on, and motors trying to turn left across them. Which is why the LCC design uses toucan crossings. You simply cannot fix this junction to be safe for cyclists without changing the way motor traffic uses it. Limiting cyclists to a short green phase is ducking the problem, and is what Kulveer Ranger describes as "designed with motorists in mind", rather than designed for a cycling revolution.

1 comment:

  1. It makes one wonder if transportation engineers ever get out of the office to examine what happens in the real world. I'm pretty sure that this facility will not make things any better.

    If this facility gets implemented, be prepared for no decrease in fatalities on the Bow roundabout in the future, that is unless all cyclists respond by simply taking the general traffic lane (in which case, studies imply there may be a 5 to 15% reduction in fatalities). However, most cyclists won't take the lane, because they'll have motorists sounding their horns and screaming at them to get in the bike lane, so they'll be too timid to cycle safely. And let's face it, most fatalities in London are probably caused by cyclists having been intimidated into cycling out of the way of drivers (and therefore out of the driver's conscious consideration).

    So, as usual, London spends more money for no improvement, because traffic engineers and politicians cannot or will not escape from the car-centric viewpoint.