Just found this great idea for tie-down

[Ed Fernandez]

Originally Posted by Jeff Lee

I'm failing to see what the difference would be if you had 4 standard ratcheting straps on the car and the front straps came loose or were magically severed. You would still have the same problem, right?

These bar type tiedowns are just an open ended hook.If the front strap/straps come loose and the car moves back,As Barry Polly said,they will drop off.A safety tie down strap won't do that.Clear now?Look at the pic of the tie down closely.
Now if they're hooked over the top of the loop on the car they might not fall off.
This is all hypothetical anyway.No matter how you tie a car down you have to make it as fool proof as possible.