My First-Hand Prius Freeway Crash Rating Experience

Holy cow, I am glad you are alright!!! Thanks for sharing your experience.

 

It's actually in the owner's manual.
Specifically, they're designed to trigger when subjected to a force corresponding to a 3300 pound vehicle colliding directly with the passenger cabin at a speed of 12-18 mph (and above) - i.e. the threshold at which the airbags would inflate for such a collision should never be below 12 mph, nor above 18 mph. They may not inflate if the collision is not to the passenger cabin, if the collision is at an angle (not perpendicular to the car's side), for low-speed collisions, front or rear collisions, or rollovers.

Given your description, I'd imagine that several of these conditions might have applied; since the hit on the driver's side was the third collision, your difference in speeds might have been less than 18 mph. It also probably wasn't straight on at the side, etc. There are several reasons to not deploy the airbags anyway - one is the high cost of replacing the airbags and the damage they cause, another is that the airbags can injure you even in "ideal" crashes and so the likelihood of that has to be weighed against the estimated severity of the crash, and another is that the airbags just aren't designed for certain types of crashes. They're designed for the most common and most deadly ones, and when you get a wild ride like yours, the padding and inflation of the bag may not be in the right spot to help, and could hurt.

Another reason that occurs to me is that you wouldn't want your airbags to fire needlessly, in case you need them later in the accident; imagine if another vehicle had T-boned you at freeway speed after you and the SUV came to a stop, for example. Obviously, the car should fire the airbags at the first point they'll be useful (if you don't survive the first impact, there's no use in protecting you from the second one...), but by not firing them when they're not useful, it's possible that they can still be used to protect you from a later impact when they are truly needed.

 

Glad you r okay and god bless.....thanks for the report...