Santa Fe Steering-Assistance System

Admittedly only indirectly related to the Prius Prime, but …

I recently managed to get some time off (luckily right before Delta started getting bad!), and took a trip to San Francisco, Muir Woods, and Lake Tahoe. On that trip, we rented a Hyundai Santa Fe. There were two things about it that really stood out in my mind.

First, this is the first time since late-2008 I’ve driven an ordinary, pure-ICE car (for more than an hour or so). I’d forgotten just how vague is the connection between the gas-pedal position and … well, anything meaningful to the driving experience! Throttle position wasn’t particularly proportional with speed, with acceleration, or even really to RPM! EVs and HEVs of course are far more precise in this regard.

Second, however, one thing I really did like about this Santa Fe, was exactly how its steering-assistance system worked. Specifically, it had no notion of either you, or the car, being in control of steering. Instead, you and the car both steer, simultaneously, all the time.
— About 90% of the time, we both agree on how to steer the car,
— About 9.95% of the time, the computer decides that it can’t confidently steer, so it doesn’t contribute to steering the car,
— About 0.05% of the time it steered incorrectly, but of course it always allows the human driver to override the computer. Doing so does not disengage the auto-steering system, though; it just trusts the human over the computer on an ongoing, continuous basis.

I think this is the best way to work. Why? Because the driver is still always, continuously, held responsible for driving the car. Until such systems are effectively incapable of failing, ever, the driver must always actively steer the car. However, the car still provides continuously-active backup steering, just in case the driver’s attention should lapse momentarily.

Is this how the pre-Prime systems worked? Having completely skipped over Gen-3, I gather that some Gen-3 Prii took more-complete control over steering than my 2017 Prime does. If so, presumably Toyota deemed that too dangerous, due to too high a risk of driver disengagement.

 

I don’t claim to know what underlying technology it uses.

My recollection is that it did a “decent” job tracking the roads going into Muir Woods from SF. It was much less successful navigating the roads going from Lake Tahoe toward Yosemite (CA49, I think it was; I’m still in shock from those mountain passes! )

 

Actually, thinking again, I think I can confidently say that it uses the lines on the road, at least in part. I say that because the only cases I can remember when it did steer wrong were when a right-turn lane branched off an it momentarily followed the right solid line.

All in all, this Santa Fe did a good job, as long as you remember all the time that you are driving the car and it is just a backup system and confidence checker; it will help a lot of the time, and has a strong chance of covering for you if your attention should lapse, but you are driving. If you find yourself putting steering pressure on the wheel (because the computer is not agreeing with you) it becomes a clue to pay even-more-careful attention. 99%(ish) of the time, that’s because the computer was not sufficiently confident to provide steering input. Only like 2-3 times that I can recall did it provide clearly-wrong steering input.