One cyclist I know calls CS2 the Cycle 'Superdeathway'. I can see why. There's not much more to it than a strip of blue paint.
Fifteen minutes lying down on one of London's main roads feels like a long time. It's difficult to stretch out fully because of all the bicycles in the way - damn bicycles! - so I'm propped on my elbows. It's cold. Above us, the lights are still on in the offices of Transport for London (TfL): a few figures stand at the windows, looking down.
This is a die-in: a silent, peaceful protest at the number of cyclists killed and injured on London's roads, especially the six cyclists who died in a two-week period in November. Before the lying-down part, there was cello music and reflection. After it comes a reading of the names of the dead, and speeches which are barely audible on the edge of this crowd of 1,000 or more.
I cycle to work every day, and on most of my days off. Six weeks before the die-in, I'd been knocked off bike cycling home at night. There was absolutely no reason for it: I was on a quiet side street; there was no traffic. I had lights and reflectors; I was wearing reflective clothing and a helmet.
The driver just wasn't expecting to see a cyclist, and so he didn't see me, even when I was right in front of him. He clipped my back wheel, and over I went, to one side.
I wasn't badly hurt: just shaken, bruised and very, very angry. But I was one of the lucky ones: in 2012 in London, 657 cyclists were seriously injured and 14 were killed. 2013 was shaping up to be a much better year, in terms of fatalities, at least - and then came November. Six cyclists were killed in just under two weeks, bringing the number of the deaths for the year to date to 14. All but one were killed by lorries, coaches or buses.
In response, London Mayor Boris Johnson said he didn't want to blame cyclists - and went on to do just that. Speaking to LBC radio, he accused cyclists of jumping red lights and ignoring the rules of the road. He later called for cyclists to be banned from wearing headphones.
There is no evidence that any of the cyclists killed was wearing headphones. There has been a suggestion that the fifth cyclist killed, at Aldgate gyratory on 13 November, may have been going the wrong way down a one-way street - but no more than that. He and the others were just trying to get from A to B on two wheels.
What is beyond dispute is the number of cyclists killed in crashes involving very big vehicles - mostly lorries. But Boris says only that he's "considering" a peak-time lorry ban and won't be drawn on making other measures compulsory, such as fitting HGVs with better mirrors, cameras or sensors.
Oh, and you know what else is beyond dispute? Three of the six cyclists killed in November were on so-called Cycle 'Superhighway' 2 (CS2) - one of them at Bow roundabout, a lethal bit of 1960s engineering with confused priorities and built-in conflict between left-turning lorries and cyclists going straight on.
Two cyclists died here at the end of 2011. At the inquest into one of the deaths, the coroner called CS2 an "accident waiting to happen". And so it did.
Philippine de Gerin-Ricard, 20, was killed on CS2 in the summer; she went under the wheels of a lorry. Hundreds joined a flash ride to call for change. There was another flash ride in July when Alan Neve, 54, was killed at Holborn by a tipper truck: that time, there were about 2,000 cyclists taking part.
When Verena Minakhmetova, 24, was killed at Bow roundabout in November, cyclists and campaigners held a vigil: about 1,000 turned out at seven hours' notice, braving the conditions at Bow to pay their respects and - again - call for change.
But change has been slow in coming. The situation is complicated still further by London's complicated governance structure. Local streets are the responsibility of the borough council but the main roads, the "red routes" are run by Transport for London, under the aegis of the Mayor of London and the London Assembly.
However, the assembly building sits on a bit of privatised land where protests are not permitted, so instead of taking their protest to the elected politicians, the demonstrators are lying down outside TfL headquarters instead.
After the deaths in 2011, TfL tinkered with the design for Bow roundabout, but the extra stop lights they put in to give cyclists a head start seem only to have made matters worse.
The priorities are unclear: cyclists don't realise that traffic is still going to come roaring at them from the right. There are no crossing phases for pedestrians at all - you just have to take your life into your hands and run. And if you can't run? Too bad.
One cyclist I know calls CS2 the Cycle "Superdeathway". I can see why. There's not much more to it than a strip of blue paint.
Meanwhile, the number of cyclists in London is rising - but not nearly as fast as it could. I've lost count of how many people have told me that they'd like to cycle but they just don't feel safe.
And you can't argue with that: if people don't feel safe, it doesn't matter how often you tell them about the comparative risks of inactivity, about the one-hour increase in life expectancy for every hour cycled, about how good you feel when you get to the office without having to do battle on the tube. If they don't feel safe, they won't do it. And really, why should they?
So make it safe. Separate us cyclists from the lorries - with proper segregated tracks where possible, with signposted quiet routes where not. Enforce the rules on lorries and their drivers: in a recent series of spot-checks in London, more than half were found to be breaking the rules.
Create the conditions on the roads that will allow children to cycle to school. Make it so that an error of judgement doesn't cost cyclists their lives or their mobility.
And yes, fine cyclists who break the rules - but have some sense. Cycling on the pavement frightens pedestrians: that's bad. Jumping a red light to get away from the lorry breathing down your neck and revving its engine: that could be a lifesaver.
Maybe then the culture will change. Maybe then the risk-averse - disproportionately women - will feel safe enough to cycle. Because at the moment, London cycling is dominated by fast, aggressive young men. Some of them - but by no means all - pay scant regard to the rules. But then, the rules pay scant regard to them.
London is changing. Where I live, in east London, car ownership is becoming a minority pursuit. In Hackney, two-thirds of households are car-free. Cycling has a huge part to play: in relieving congestion and strain on public transport, curbing pollution, reining in obesity. So why not make it easier for people to cycle?
Instead, for now, cyclists are being knocked down, injured and killed. And there's huge anger about that: among cyclists, among would-be cyclists, among their families. And among advocates for safer streets for all: 69 pedestrians were killed in London last year but while the capital's cyclists have found their political voice, pedestrians are a more diffuse and muted group.
So why should anyone outside London care? Simply because there are enough cyclists in London to make a real difference. Cycling has gone up by anything from 80% to 200% in the past decade, depending on whose figures you read. At some junctions in London, up to 75% of peak traffic is now made up of people on bikes.
Other towns and cities have a higher modal share overall. But London is in a uniquely prominent position. What happens here has the potential to influence the politics of transport for the rest of the country, and that's why it's so important to get it right.
Friday's die-in was modelled on protests in the Netherlands in the 1970s, called Stop de Kindermoord (Stop the Child Murders). Those protests succeeded, turning the Netherlands away from car domination and towards the model for mass cycling that it is today. Can Britain follow suit? Let's see.
I'm glad I went and lay down in Blackfriars Road. I'd rather not do it again, but I will if I have to, and so will hundreds of others. TfL, are you listening?