Gyratory traffic schemes, extended one - way systems etc

oliver, what's your evidence base here?

For what specifically?

cycle-bus interaction is a big problem - maybe not for you, but for many other less experienced or confident cyclists, certainly. it has resulted, as you know, in several recent deaths and injuries in central london.

Well, show me your evidence that it is a big problem. I'm quite aware of recent crashes and deplore them, but I have yet to see any evidence that it is a big problem. There may well be such evidence, but buses and HGVs don't show up very clearly in the stats.

protected space for cycling isn't a blunt, non-specific remedy. it's a very specific remedy where cyclists interact with heavy bus and hgv traffic (which is many places in central london).

As you know, this is not how it is generally portrayed. The bloggers' view is that it's 'the only thing that works (with the implication "for everything that's concerning about cycling")', in all conceivable situations, and that it has to be everywhere. It is blunt and non-specific, as it is meant to address all problems at once. It's just blogs, of course, so they're not to be taken too seriously, as they're full of poor-quality information, but that is generally the argument put forward today.

Your own argument may be only that segregation is to be pursued for the specific purpose of reducing crashes or 'increasing safety', but that hides the fact that 'safety' is a fairly complex concept (and a very misleading one) and can't be considered in specific isolation. While they talk about 'safety' all the time, such specificity also doesn't appear to be in the view of most people advocating these measures.

(For the record, segregated sidepaths (it's worth clarifying that we're only really talking about sidepaths here, as this is the only aspect of 'segregation' that people are normally at loggerheads about) have only been shown to reduce crashes (and not reduce cycling) where such networks are well-near complete or complete, where cyclists have priority at junctions, and where cyclists are banned from using the carriageway (i.e., where separation is so complete that any interaction is nearly designed out); in all other scenarios, segregated tracks contribute to increased collisions at junctions. I also happen to think that the crash rate in the Netherlands is surprisingly high compared to some of the elevated claims that are made on-line. It is still commendably low, but not as low as you'd expect from some of the flannel that you read about it.)

car/cycle accidents at 20mph or less tend to be less serious - and cars have better visibility. cycle/hgv/bus accidents, even at low speeds, often kill and maim. it's just true that safety here, where traffic is mixed, depends mostly on the competence and alertness of the driver of the large vehicle, and to some degree on the competence of the cyclist, and neither of those can be guaranteed. it's better to rely on safety by design.

Some of what you say here is true, but what appears to be meant as a conclusion does not follow from what goes before. For the record, again, from what I've seen, there is no serious crash problem with buses in London (but as above, I'm perfectly open to being corrected on that). The crash problem that we do have is with HGVs, and it is, again, a very specific problem (mostly to do with left hooks) which warrants specific intervention. It does not warrant complete separation of these modes (the blunt instrument), and certainly no mode of intervention whose key weakness is junction treatment. There are no guarantees in life (and certainly no blunt and all-encompassing ones). For the record, addressing driver competence, driver working conditions, vehicle design, etc. (see the LCC's 'No More Lethal Lorries' action plan) is by far and away the most effective way of addressing the potential for such collisions; you simply do it at the level of the perpetrators, as there are far fewer of them than potential victims.

(For what it's worth, Amsterdam has an HGV problem, too:

Biking: Watch out for trucks turning right. In 2006 four of the six (6.33333333) people who died in Amsterdam bike accidents were killed by trucks turning right.

From: http://www.tobysterling.net/2007/12/bike-accident-deaths-in-amsterdam-and.html

I believe the picture is the same all over the world. Of course, the Netherlands have a lower crash rate than other countries, but the HGV problem is very serious even there.)

the majority of cyclists (and those who would like to cycle) feel safer (and, in most cases, it appears, are safer) when not mixing with buses/hgvs

Oh, don't get me wrong, we all like motor-free streets (in Hackney, we've just had one created, in Goldsmith's Row). There's no argument with that. (Again, your lumping together of buses and HGVs doesn't do justice to the relative risks associated with either.)

have you been to manhattan recently? many miles of new protected space for cyclists - often on avenues with plenty of frontage activity and side streets - appear to have resulted in a significant increase in cycling.

http://transportationnation.org/2011/07/28/breaking-new-york-city-biking-is-up-14-percent-from-2010/

No, I've never been to NYC, but of course I'm aware of what's happening there. There is, as ever, no evidence that it's the cycle lanes/tracks specifically that have caused an increase in cycling. (The evidence from all over the world only allows the conclusion that the absence, presence, quantity or quality of cycle facilities is completely irrelevant to any increases in cycling. Cycling has increased significantly in a lot of places that haven't built much by way of facilities.)

One key aspect of the NYC cycle lanes/tracks is that in a number of places they permit two-way cycle traffic (while the street remains one-way for motor traffic). Prospect Park West, in the picture with the article to which you linked, is an example:

You can see what a huge advantage this connectivity creates for people who cycle compared to congested one-way conditions for drivers. You can do that under the conditions pictured, e.g. little frontage or side street activity (other places in NYC may have more of those, but generally conditions in Manhattan are much more uniform and predictable than in busy London streets on much older street patterns).

This, permeability, is generally one of the factors that can be directly and specifically shown to cause increases in cycling. Another demonstrable factor is high-level political support (many people do follow what people in government say), and of course the sensational urban realm interventions like Times Square (as of now, we can only dream of those in London). Cycle lanes/tracks are an unimportant sideshow in the big overall picture of which policies are effective, whether you're in NYC or in the Netherlands. It'll be interesting to see if the growth in NYC is sustained. In London, we've had roughly about 10-15% growth per year since 2000 (by the best measures we have, which aren't very good), with much weaker Mayoral support than over there, e.g. little appetite for daring public realm interventions.

what is needed, certainly, is a degree of imagination in terms of the re-thinking of roads and junctions, and a political willingness to take space away from private cars.

Try not to think so much in terms of 'space'. That's really not very important and is a massive red herring. Try to think more about the principle of through traffic. The ability of driving large polluting carriages through most streets is the main concession to motor traffic in London. When you address that, you've won most of the battle. You can give as much space as you like to driving; as long as there's only a coarse-meshed network of through routes for motor traffic, as well as a fine-meshed network for cycle and pedestrian traffic, people won't drive as much. When people talk about 'space', they normally don't challenge the idea of permeability for motor traffic.

(We are, by the way, agreed that considerable changes to infrastructure are required. We may just disagree on their nature. I only mention this because I sometimes get accused (rather bizarrely) of being an 'integrationist' and not wanting infrastructure changes. I want much bigger and more wide-reaching changes to infrastructure than any 'segregationist' I've ever met. (I put these terms in inverted commas because I'm not into pigeonholing people.))

(and, obviously, you're right - it's way better to remove a gyratory entirely than try to fit it out with cycle lanes.... but that doesn't mean that protected space shouldn't be part of the redesign..)

It does mean that, actually. When a gyratory is returned to two-way operation, there is very little purpose left for segregated tracks, which are mainly effective as contraflow facilities, or for unusual scenarios such as a tight turn around a blind corner. There are very few specific purposes to which segregated tracks are suited outside of a gyratory system. You can still call them in as a blunt instrument, of course. ;)