Cycle campaigning

^ They may not be but they're still there...or am I missing the point?

Also aren't the Cycle Superhighway a TfL routes? they may not be the inventor of the ASL, but they're still promoting it.

Well. It's hard to know what to reply. ASLs are generally-accepted highway engineering practice, endorsed in TRL trials etc. They're used in other countries, too (albeit in different shapes). TfL are not (often) in a position to do their own research (that's left to people like TRL) or to come up with their own original ideas (and when they do it can become a shambles like the motorcycles in bus lanes trial).

If you want to go up against them, you have to contend with a number of difficulties. Firstly, a lot of people believe that they make things safer, and they are in particular demanded by a lot of cycle campaigners and fetishised by a lot of riders who see in enforcement of compliance with ASLs by drivers some kind of quid-pro-quo for the kind of enforcement that's targeted at bike riders (e.g., RLJing) to highlight that it's not only people cycling who commit offences. Many inexperienced riders are, of course, very keen on getting to the front of the queue because they mistakenly believe that this always reduces risk, or even RLJing as facilitated by ASls and lead-in lanes. It's not just TfL that put these things in for their own pleasure, it's because a lot of people tell them to.

Secondly, the evidence either for or against is pretty inconclusive. Essentially, they don't seem to make much of a difference, except in some unusual cases. Yes, in theory the lead-in lanes along the nearside may place riders at greater risk than if they hadn't been there, but in the absence of the lanes, riders would probably do the same filtering along the inside (implementation of ASL lead-in lanes doesn't tend to change much about carriageway layout, e.g. lane widths, although it may in some cases), and they also generally don't reduce the chance of drivers obstructing the nearside. Also in theory, the ASLs may place cyclists in a more prominent position at the head of the queue and so prevent them from being involved in left hooks. I say in theory, because there isn't a great deal of evidence either way.

Thirdly, they were devised in response to an existing state of affairs that people wanted to change (lack of stop line compliance by cyclists, cyclists mixing it up in traffic queues, which can have the effect of making queues move more slowly, and the hope that if cyclists were got to the front of the queue you'd get fewer left hooks, etc.). You go right ahead and try to show that ASLs are not the right response--it's not that easy. The problem is that there are no alternative 'standard' measures designed to address the above issues, so what are you going to come up with that makes a difference?

My own response is that I don't think that 'standard' measures are a good idea. When I deal with a traffic scheme, I try to think it through on its own merits, at its particular location, and under the particular circumstances affecting it, and then try to come up with the best possible solution. Who knows? There may be a situation in which ASLs are a good idea, and that will emerge from thinking carefully about the design.

A lot of people demand design 'standards', though, and would not be happy to leave the judgement on design fully to individual engineers, who have to apply the standard measures somehow, which can then dictate constraints that may worsen a scheme.

On the whole, I consider the debates about ASLs as a bit of a storm in a teacup (perhaps a good starting-point for learning about highway engineering, but many people never progress beyond thinking about visible, superficial things like that). They're low-level measures of no proven great danger or great positive effect and until I see evidence that makes me think that either having them or not having them is conclusively supported, I'll reserve judgement.