I was first on scene to a fatal RTC outside my old house. A car load of foreigners thought the road they were on was still dual carriageway, as it had been for the previous 40 odd miles. It wasn't. Straight head on collision Laguna V Rover 214. Driver of the 214 died pretty much instantly as the blade from his folding entrenching tool entered his neck from behind. Nothing anyone could do for the chap. The rear seat passenger of the Laguna also died from hitting the drivers seat.
There was a load of crap in the back of the Rover , as he was a landscape gardner, no parcel shelf or dog guards.
My friend SteveV also got whiplash from his acoustic shelf when he projected his Scirroco into a wall on a bend where a lorry had dumped a load of derv. The 2 x 10" speakers, and the 2 x 12" speakers mounted in 1" MDF weighed a ton, and in the rapid deceleration launched themselves from the back of the car to the front, bending the head restraint and Steves neck.
So it is something to be aware of , things like car jacks and wheel braces in open estate car boots.