There are many 2 or 3 car pile-ups where several people die day in day out every week of the year.
Yes, probably caused by drivers who drove with similar attitudes (not prepared to stop in the distance seen to be clear).
I wonder what happens if a cyclist shot out of a one way street the wrong way, causing a car to swerve and have a head-on with a bus/lorry the other way? Or mounts the pavement and hits a busy bus stop?
Is that the fault of the motorist for not anticipating what might happen?
Yes, you can slam on the brakes without checking the mirror in an emergency but you should not swerve without looking or having already looked recently. [Without working ABS, the driver might unwillingly swerve, admittedly.]
That said, I once slammed on the brakes after a cyclist pulled out in front of me, didn't brake correctly (I did both brakes not front brake only which is a bad idea because the front brake lifts the back wheel up and causes back brake braking to skid the tyre). I managed to keep control down to about 5 mph then clipped the curve.
My fault for not knowing how to brake correctly and not being in the middle of the road. (I should have ignored the cycle lane).
Road closures of this nature are already common, not really to improve cycling, but so that fewer households are blighted by heavy traffic. This is often accompanied by traffic calming. New housing developments are usually built like this to begin with, with most streets being dead ends and few, if any, houses built on the distributor road feeding these streets.
Here is a journey in Netherlands which is 1 min by bike and 10 mins by car:
http://goo.gl/maps/pHzNn
Although it'll reduce car traffic by far, it might results in the users of paths being subjected to more muggings/sexual assaults than if the roads had through traffic. So having roads shared with car traffic isn't always a bad thing. Personally I'd prefer both, traffic-free routes for rush hour, and shared roads with natural surveillance for nights.