Cycle campaigning

It's basically what happened in Holland, Belgium, Copenhagen etc.

Not so much in Belgium or in Denmark, to the best of my knowledge.

Some streets were simply closed to motor vehicles. Some were made "shared" - I think this latter is the norm, but I personally believe you need Strict Liability laws in place to make shared space work for cyclists and pedestrians.

No, I don't think you do (by the way, people talk about 'stricter liability' ('strict' liability would mean that in a collision of sail with steam, the steamer would automatically be liable; 'stricter' means that the onus is on them to show that they are not liable (which is fair, as the sailing party is not at fault in the vast majority of cases). Right now, it is generally the injured party, who may have passed out, been unable to gather witnesses, etc., who has to prove the steamer's liability.

I've discussed this idea with Oliver before. Hackney have actually done it with a few short stretches, such as the back road from London Fields to the Town Hall.

That's Goldsmith's Row, and we're very proud of it. Wait for Phase 2, which is about to go on site if it hasn't already. It'll be pretty. And most credit of course goes to Hackney's excellent officers and politicians.

(Note that this is both a 'shared use' scheme (slightly different from the idea of 'shared space') as well as an example of modal filtering.)

The City have done it with that bit from Southwark Bridge to Poultry. Tower Hamlets have done it in Poplar.
Filtering has been done all over the London. The best example is in De Beauvoir Town, but Lower Clapton north of Powerscroft Road also has it. There are others, e.g. parts of Barnsbury. Generally, a lot of historic rat-running was treated by means of 'road closures' (which often didn't permit cycle access, e.g. high kerbs, etc.). This was mostly not doen thoroughly enough, so that rat-running was often merely shifted one street further along.

Counter-intuitively, models show that it can actually improve motor traffic flow too - there was a thought-provoking study that suggested it would be better for motorists if Blackfriars bridge was closed to them. I think the idea is that although the journey may be longer, it's quicker because it is not interrupted so many times by cars joining from newly closed roads, and in addition everyone's going the same way.

That can certainly happen; studies show that modal filtering can cause 'evaporating' motor traffic of up to one third of existing motor traffic flows. Basically, a lot of pointless trips (trips that could easily be made by a more suitable mode) simply shift to other modes--some people drive distances that they could walk in the same time. The economically-important trips tend to remain, as they can't be avoided.

If a road is going to be ruined by narrowing, making it one-way, closing off one end, closing an exit, etc, (such as outside the Roebuck) I would consider closing it to motor vehicles entirely. At first this needs nothing more than a road sign and maybe a plastic barrier such as those on the "ring of steel", then later it can be made pretty with planting, blockwork, etc. You could at that point install droppable bollards to allow emergency vehicles through, and equip the vehicles with the means to drop them automatically when running on blues and twos.

It can indeed be very quick and easy to install such measures, as demonstrated a few years ago by the speed with which the City put in place the 'Ring of Plastic', which took all of a week-end.

The next, and more adventurous stage would be to consider new roads for closure. For example, why not ban motor vehicles from the Strand? You can route everything down the Embankment via Northumberland Ave or Temple Place. Could we implement two-way running on Gower St and remove motor traffic from Tottenham Court Rd?

You're probably aware that the latter is going to happen soon.

Just to make clear why I think the cameras idea is a non-starter:

The thing about average speed cameras is that they are splendidly and almost completely effective in reducing speed to the posted limit.

Average speed cameras have proven very effective in some circumstances, but they are certainly not to be applied indiscriminately.

But with such low levels of non-compliance they are not revenue raisers, and they are very expensive to install and operate, so it has to be economically worth it. They are designed to limit continuous average speed, not maximum speed in a stop-start situation.

As a result I cannot think of many (or any) London roads which could be effectively policed by pairs of average speed cameras.

Yes. Tower Bridge is one. Very high levels of motorist compliance.

I'm not a big fan of techno-fixes quite generally; while vertical deflection (humps, cushions, etc.) clearly reduces crashes and saves lives, I find it annoying that it attacks the very useful principle of a road or street, a flat surface on which it is easiest to travel by mechanised carriage. I'd replace 20mph zones with systematic and consistent filtered permeability. With relatively small zones, high burst speeds by motor vehicles would be quite unlikely. You could still implement such a limit, but it wouldn't really be necessary on filtered streets. However, it would be very useful on more major streets (the 'coarse-meshed network') which could not be filtered.