Hacker News Reader

Comment by greglindahl | Hacker News Reader

Previous article and discussion of Toyota's safety-critical firmware woes:

https://news.ycombinator.com/item?id=6636811

Edit: and the title got edited to be the NYT title, which obscures the relevance to Hacker News. Ah well. This settlement is directly related to the court case Toyota recently lost, with expert testimony about the poor quality of Toyota's embedded safety-critical firmware...

View on HN

The people making comments about killing the engine is a monumentally bad idea. If the car has a conventional key ignition, turning the key even to the accessory position can engage the steering wheel lock. Without a running engine, you could lose power brake and steering assist. Not all power steering systems are hydraulic, some are pure electric and some are electro-hydraulic. The majority of braking systems are assisted by a booster driven off of engine vacuum. You have two or three pedal pumps before the vacuum is gone.

Difficult steering/braking seems like the better of two bad options if the car is accelerating uncontrollably.

The handful of cars I've checked (after Bob Pease wrote about it) won't lock the column unless you remove the key. Some might lock, but only when the tranny is in park. Worth checking out.

Do you even want/need power steering assist in a runaway situation?

When a car with power-steering loses power, it doesn't become like a car without power-steering. I've had a car shutdown at highway speeds, and turning the wheel is incredibly difficult. At the time I was a fairly muscled weightlifter, and I could not turn the wheel more than a few degrees (I managed to change one lane into a turn off).

mzr's comment above gives good advice: don't turn off or remove the key in a moving vehicle. Shift to neutral if the gas pedal is stuck.

This is correct. In cars with hydraulic-assisted steering, you're forcing fluid back through the pump, which is quite hard to do in addition to the fighting the bulk of your car and steering rack. In cars with electric-assisted steering, like the Prius, you're working against the electric motor using a belt and pulleys.

Which begs the question: why isn't the electric-assist motor designed to freewheel when power is lost? Losing steering assist at speed would be a more manageable situation.

> Do you even want/need power steering assist in a runaway situation?

In my sole unintended acceleration incident (floormat) I was beginning (but committed to) a turn. I put the car into neutral and came out of it okay. (people forget that any modern engine has a rev limiter so neutral is really pretty safe)

It would have made a bad situation worse for me if I had lost my steering. I've lost steering on that car (lost the generator for a few seconds in the wet on two separate occasions) and I can confirm what someone else said about the steering getting quite heavy.

If the key is in the ON, or ACC position the steering lock will not engage[0]. I do agree that killing the engine should not be the first thing to do. It should introduce a fuel or ignition cut to lower RPM (like some cars do in neutral to avoid users from doing neutral to drive WOT drops).

[0] I used to work on cars for a living.

But after the engine stops, which would hopefully take no more than a second or two, the key can be quickly returned to the ignition point, without actually restarting the engine.

So at worst the steering would be locked for only a second.

Reply on news.ycombinator.com