Yeah, but if they really want to be safe they need to eliminate the possibility for that type of accident.
Even under the safety car the F1s aren't really going that slow. Plenty fast enough that it's conceivable that they could aquaplane, spin, skip over the gravel and hit the JCB. The car would be going slower, obviously, but de Villota wasn't actually going very fast when she hit that truck either, she just got unlucky with how it hit her.
Even under safety car I could see it being possible that a very similar accident could happen, especially in that spot. There really isn't that much space between the track edge and the barrier, the safety is mostly based on the fact that the cars will strike the barrier a glancing blow in all but the most bizarre of accidents.