Re: Mansfield bars
Have look at the state of the Tesla that a bunch of German kids took for a drive at huge speed, took off via a "ramp" and landed nose first in a field after going up to about 25m high - http://bgr.com/2016/05/08/tesla-model-s-accident/ - they all survived.
This shows how survivable a crash can be when the impact is onto the front of a car, which can then "crumple" as designed (especially true with a Tesla with no engine). The same is unfortunately not true when the point of impact is the windscreen (windshield to Left-Pondians), followed immediately by the front occupants' heads.
About 20 years ago, the wife of a good friend of mine was killed in a similar incident over here before the bars became mandatory and it was determined that she would easily have survived had the bars been present, so this is a subject very dear to my heart.