Cycle Markings in London

Some of those denote the LCC cycle routes, which Boris wants to incorporate into the 'quiet way's network he suggested. There is an LCC route round the corner from where I live and I used it as part of my commute to my old job. They are quite good actually as they keep you off the main roads and while on a map they look longer, avoiding traffic congestion and traffic lights means that commute times are pretty good, as well as being less stressful and a lot safer. They're a lot better than the Cycle Superhighways, which run for the most part along busy roads and where the illusion of safety provided by the blue paint is just that, an illusion, as can be seen by the rate of deaths an injuries on them.

It would be difficult to say because no one attention there, they just have to mean to drive or ride their vehicles. but as "Gizmo_" said It's just to alert drivers that the route is used by cyclists. Amusingly however, most drivers don't actually know this either.

Regards
On Yer Bike - Robert

You also get them on cycle contraflows down one way streets - to let the driver know bikes are coming. The driver ignores this and beeps and swears at you. This is also the law.

A cynic might suggest they are a way of spending cycling budgets when you have got targets to meet and no idea what to do with the money. In essence they're the chocolate teacup of cycling infrastructure as said above.

What he said. It's just to alert drivers that the route is used by cyclists. Amusingly however, most drivers don't actually know this either.

Legally none, they are intended to alert to the possible presence of bikes.

And a few are on some old bike routes.