Street tracks has to conform to the same strict rules as the regular ones. That's why they usually have much smaller average speeds, so things like huge run-off areas are not needed. Take a look at your video again: only in one place the car reaches 300km/h. Crashes on street tracks happen quite often (less room for errors), yet I can't recall any serious one. Ok, Kubica's shunt in Montreal looked scary - but Circuit Gilles Villeneuve is a semi-street and unusually fast track. The new ones are fine (safety-wise), really. Open cockpits and loose wheels are the big issues for now - both being currently worked on.