I think the equivalent of jamming a block of solid aluminium into a spinning blade would involve some kind of anchoring. It would ruin the car and likely damag

I think the equivalent of jamming a block of solid aluminium into a spinning blade would involve some kind of anchoring. It would ruin the car and likely damage the road but as long as the passengers can be protected from the rapid deceleration, it just might save a life. OTOH you could just wrap the entire car in airbags and protect pedestrians the same way you protect the passengers. Not sure how practical or useful that would be, though.