Stupid Prius Tricks – Traction Control Distractions
I love my Toyota Prius. I’m very grateful to Google for giving me
a financial incentive to buy a brand new car which does everything I
want. It’s totally big and practical, it’s very high-tech, it both
supports and projects my values,
etc. I could sing its virtues for pages. But for now, I want to share
some non-obvious things about it in a series I’m calling "Stupid Prius
Tricks." (With a tip of a hat to David Letterman.) Several of these articles (like this one)
are complaints, but this must be taken in the context that overall I love the car.
The Prius’s High-Tech Safety Features
The Prius has at least a couple of smart traction control systems which use technology
to help maintain control of the car in difficult situations. Of course
there’s anti-lock brakes (ABS). In addition to ABS the braking system
does things called Electronic Brake-force Distribution (EBD) and Brake
Assist. Beyond that, it’s got Traction Control, and in all but the
stripped-down cars something called Vehicle Stability Control (VSC).
What each of these features does, or how they differ from each other I
don’t know and don’t frankly care. They help the car do what I’d want
it to do under good driving conditions when the road is slick or uneven
or I’m driving too fast or what have you. All this is great. But
there’s one subtle and very bad flaw in the implementation of at least
one of these systems.
The Stupid UX for these Features
When the Prius needs to engage one of its TLA control systems, an
orange light appears on the otherwise dark dashboard. Sometimes a
sound will beep. This is presumably done to let you know that the
fancy feature that you paid for is working on your behalf. Call it a
marketing feature if you will, because there’s nothing you can do with
this information, or way to react to it within the vehicle’s controls.
The stupid thing about this feature is that it’s distracting to have
lights flashing and sounds beeping. When you’re having trouble
controlling the car is the last time you want something distracting
you. So the engineers at Toyota have done something completely moronic
– a complex system senses when you’re having trouble controlling your
car, and chooses that time to throw more distractions at you. I’ve
observed the light and beeping on when driving over bumpy roads, or
down
something very steep that has a rut in it, or when the back-right wheel
accidentally jumps up the curb. None of these situations I’ve gotten
into have been serious or very dangerous. But even still, they were a
bit confusing, and the confusion was confounded by having the car meow
at me demanding attention. When the car is not doing what you expect it to, the last thing you want is additional distractions. Bad choice, Toyota. These features should be absolutely silent.
What you can do about it
If anybody knows a cheat code to disable this light or beeping, please
post it in a comment. Until then, you can help a little bit by putting
a small piece of electrical tape over the orange light with the symbol
for "I think you’re losing control of the car."
ABS pumps the brakes so that you can steer while braking. EBD moves braking power between the front and rear brakes, as appropriate. VSC uses gyroscopes to detect when the desired (ie, steering wheel position) motion of the car and its actual motion differ, and transfers power to different wheels to get your motion closer to desired. And Brake Assist detects when you are "panic braking" and puts the brakes on harder.
This certainly does sound like a user interface flaw — if you are a good enough driver to know to steer differently depending on whether ABS is engaged or not, then you are also a good enough driver to feel it kick in through the brake pedal.
It may be a bit distracting, but I have seen it in more cars. I drive a Prius myself, but it has not bothered me. In fact my previous car, a Renault Scenic, had the same warning light when VSC was active. (I don't recall hearing a beep in the Prius when it is active. Could be a difference of the EU-version?) Anyway, during a real emergency you won't have time to notice the light as I know from experience.
What really surprises me about Prius, is that with all the information it shows about fuel consumption, it does not show your action radius! That's what I call stupid.