Monday, September 01, 2014

Don't drive home wet

We all expect our car’s airbag to work in the case of emergency.  So what happens when it has been automatically shut off without warning?

We thought something was wrong with the airbag shutoff switch in our 2012 Subaru Impreza.  We’d be driving along, and all of a sudden the passenger airbag would shut off, leaving the passenger unprotected.

So we called the dealer and had the switch checked (more than once!) No problem, we were told. Maybe the passenger shifted her weight and the switch turned off.

Then, this week, a service attendant mentioned that the on-off switch had nothing to do with weight. It was based on the amount of water in a person’s body.

The light went on in our minds. It turns out that the airbag would shut off after a few minutes when we were driving home from the beach and the passenger was wearing a wet swim suit or sitting on a wet towel! It would stay off until the seat dried out.

We checked this out. Here’s how one Subaru dealer explains this on their website:

Most Occupant Detection Systems measure the weight of the front seat passenger, to determine if the front passenger seat airbag should deploy.

All 2012 and 2013 Impreza and 2013 BRZ models use a new type of Occupant Detection System called Electrostatic Capacitance Sensor ODS. This system does not use weight to determine whether to turn the Occupant Detection System ON and OFF. 

The Electrostatic Capacitance represents a material's capability of storing an electrical charge. 

When water or anything with high moisture content is spilled on the front passenger seat cushion, the airbag is designed to remain OFF until the seat cushion is dry.  This will also be the case if the passenger has moisture on their clothing, such as rain-soaked pants or rain gear.  In each of these situations, the airbag status may remain OFF even if a passenger is seated.

Passengers are advised NOT to sit in the front passenger seat if the seat cushion is wet or if their clothing is wet.  The best way to ensure proper operation is to keep everything off the front seat except a passenger. 

We don’t recall getting notice of this when we bought the car.  And it was clear that the service department staff didn’t always think of mentioning this system when an owner brought up the issue of the airbag cutoff. And if you search for “Subaru occupant detection system” or “Subaru passenger airbag shut-off” on the web, there is no official notice from the company.

There is no warning about this shut-off system on the passenger side visor. And, if you check the owner’s manual, there is nothing about this issue in the opening section’s safety precautions, although there is material about the speed and force of airbag deployment. Later, embedded on page 42, there is this advisory if you happen to turn to that page: “If the front passenger’s seat cushion is wet, this may adversely affect the ability to determine deployment.  If the seat cushion is wet, the front passenger should stop sitting on the front passenger’s seat. Wipe off water from the seat immediately, let the seat dry naturally and then check the SRS airbag system warning light.…”

Let’s say you’ve never noticed this “feature.” You’re driving home from the beach on a crowded highway at 60 mph with your family in a full car, and the passenger airbag shuts off. Perhaps you see the shut-off light suddenly illuminating. How exactly do you stop the front passenger from sitting in the front passenger’s seat? Perhaps you don’t even see the shut-off advisory light, in that you are focused on the holiday traffic. In either case, your passenger faces an unexpected hazard.

Many Subaru owners are outdoor types who will drive home after a jaunt to the beach or a hike in the wet woods. How many of them know they are in danger when they do so?

How and why did Subaru decide that this kind of automatic shut-off mechanism was superior to one based on body weight? Don’t they have an obligation to better inform the owners of these model cars? This is a product design lawsuit waiting to happen.


Medical Quack said...

Welcome to the world of marketing the "proof of conecept" (grin). I see your point and today we have a lot of broken software models out there as there's so much money in development.

That may or may not be the case here with buidling a better mouse trap but yes it's a pain I could agree with you there.

Too many folks are living in the "Grays" today too, confusing virtual values with the real world and I'm sure you might agree with me too, nobody seems to disagree on that one we see some "stupid" stuff out there.

"People don't work that way" is my explanation for a lot of this and we are not algorithms either. Now for a tech person to be saying such, you might guess that some of us are a bit fed up, yup. It's not just me, take Larry Ellison too who's software engineer/CEO extraordinaire...

It's hard to get the right match sometimes with humans and software and we do have some failed models out there today for sure.

@Hem_Onc said...

From Twitter:

I wonder what the rationale was for this design. Is avoiding a false deployment worth the risk of not working when it should?

Mark Graban said...

If we define quality as "fitness for use," then this fails miserably.

I can't believe Subaru signed off on that design.

OK, not to be a Debbie Downer, but far more people will die due to preventable medical errors than this Subaru design flaw...

@TerryFairbanks said...

From Twitter:

This is an absolutely ludicrous design.

Stephen H. Owades said...

From Facebook:

It doesn't seem like a smart alternative to the standard weight sensor, but I can imagine why they thought it might be. I often keep my bag on the passenger seat in my car if I have no passengers, and getting a "fasten seat belt" warning if the bag is too heavy can be annoying. I think that same weight threshold also turns on the passenger airbag. My guess is that Subaru heard enough complaints about the operation of their weight sensor and figured that a sensor that only triggered for "meat-like" objects would eliminate those complaints—but then they thought they had to deal with the counter-situation of a spilled drink or wet towel by turning the airbag off if there was too much water present. Not a smart choice overall, and the fact that they reverted to a weight sensor for 2014 suggests they realized that (eventually).

Anonymous said...

Thank you Stephen for that! Subaru had thousands of complaints with the old weight system and changed it. As the technology became more effective, they were able to go back to the weight system in 2014. I do not understand why people automatically believe that a companies decision are always based on malice. Subaru did what they thought was best for the customers due to feedback. Whether or not you believe they made the wrong decision, it was based on customer feedback. These blogs are horrible and can ruin a company based on one person's anger and lack of knowledge as to why. Do you research, call Subaru directly and find out the facts before feeling the need to express anger that is most likely not derived from this issue but your own need to complain about anything and everything.

Paul Levy said...

Excuse me: "your own need to complain about anything and everything"? Where did you come up with that?

Please address the issue substantively and don't cast aspersions.

Perhaps someone from Subaru could provide an answer--here, for all to see.