Runaway Car

[Onuris]

I seem to recall a similar situation back in the late 80's or early 90's, it was either with Audi or Volvo, can't remember which. Ended up being a few instances of operator error from what I remember.

 

[LukeA]

I, too, have a dumb question... Why don/t they make the brakes on vehicles more like the air brakes on big rigs, as in, you release air pressure by stepping on the brakes, and the loss of air pressure causes the brakes to apply?

I do however, realize what a cost this would be to automobile manufacturers, with additional r+d manifested in higher prices, but then you couldn't have brake failure.

Because those systems are more complex, heavier, and bulkier than power-assist fluid brakes.

And: FLUID BRAKES DON'T FAIL OFTEN AT ALL. There's a hundred years of engineering behind them that makes them extremely safe and reliable.

 

[InTheDark]

I have a really dumb question, but if I had a "runaway car" couldn't you put it in neutral (or manual transmission out of gear)? Then it seems the brakes should stop it even if the engine is running to beat the band.

Probably the only logical piece of advice in this thread.

Shift into neutral, and it doesn't matter what the engine's doing, the brakes won't know. All this talk about shutting the car off, throwing out the keys, holding the start button down, scares me just thinking about it. Not only will you lose power steering, power brakes, and possibly lock the wheel, why risk that rather than just push the gearshift up one notch? Sure, you might damage the engine, but better than crashing the car. Also, I'm not sure why people think there's any advantage to a manual, neutral is neutral no matter what type of transmission.

IMO, no matter what the cause is, either floormats, or electrical glitch, there's still operator error in handling the problem. Either because of panic, or ignorance, but no matter how many failsafes you put on a car, you're always going to have accidents if people don't know how to react.

And those people who think older cars were somehow immune to these types of problems, have you driven an older car lately? I'm driving a 35 year old vehicle everyday, and for all the faults of these newer cars, it still an order or magnitude better than it was before. Pinched cables, broken return springs, sticky throttle shafts are all common problems that you just don't hear about, because if it happens it's not big news.

 

[Patriot]

I have a really dumb question, but if I had a "runaway car" couldn't you put it in neutral (or manual transmission out of gear)? Then it seems the brakes should stop it even if the engine is running to beat the band.

Yes, I don't know of any auto trans vehicle that can't be placed into neutral at any time. Problem solved.

Many manufacturers using fly by wire throttle control won't even let the throttle and brake be used at the same time. If you try to "two foot" them and ride the brake the throttle cuts out. Obviously, this is an electronic "smart" function although it was also possible before fly-by-wire systems via the "stop lamp switch" on a separate circuit telling the throttle actuator to close.

Regarding chucking the key out the window, yes, it eventually works on a Mercedes-Benz and BMW but I'm not sure about Lexus. The key phrase here is "eventually" since the distance and time varies. Sometimes it's several seconds after the range is exceeded but on the older "smart key' systems the car could be driven until it was turned off manually, at which time it couldn't be started without the key present. Also, since no one really knows what's going on just yet, it could be argued that if the fly-by-wire throttle control was misbehaving already, what guarantee would there be that it would listen to a "no go" command from the "keyless entry/drive?"

The answer to this type of situation is to apply one continuous maximum brake pedal input (no pumping) and shift to neutral.






With regards to people being unaware of their vehicles limits, that's practically every driver on the road today. I mean the average person just doesn't have to brake, turn, or accelerate at maximum rates unless they foresee and accident, but since they've never been instructed or learned through practice they typically don't respond correctly when faced with an event.

At the center of this topic is braking. There are many studies that reveal that accident victims typically only used 50% of the maximum braking effect inherent in the vehicle. Because of this, Manufacturers are installing these smart systems like "brake assist" in order to improve accident avoidance. One of the control units, (usually ESP) monitors several parameters including pedal application speed and force to determine if the driver wanted maximum braking or not.

As a Service Advisor for many years with Mercedes, I experienced weekly occurrences of various braking complaints from customers, which all had to be addressed seriously because of the nature of the system. Often the complaint was that "my brakes feel weak." After a quick on the lot examination of fluid level and pad thickness I'd go on a test drive with them. After making sure everyone was buckled in and upon reaching a empty street, I'd perform a maximum stop from about 50mph in typically about 100 feet. This causes their jaw to drop and comments like "I had no idea my car could do that!" Then I'd say, "your turn" and we'd do it again with them driving. There's a reluctance for the average person to apply the brake with enough force to actuate the ABS system but after a couple of tries they do it. Sometimes it's the first time they've ever felt the ABS activate or seen the ABS light displayed on their cluster. This usually resulted in big smiles and increased confidence in their car and their own ability to stop it. Many issues were solved this way, with a bit of patient instruction.

 

[Mjolnir]

Audi did have a similar problem to this one back in the 80's. However, I believe that it really was operator error.

I have a car with keyless ignition, and it will remain on (the engine too) when the key leaves the leaves the inside of the car. It will flash "no key" (or something of that nature) on the dash and beep, but it will not cut the engine. The system seems to be able to distinguish if the key is outside or inside the car. It shows that there is no key if the key is not inside the cabin, but it can obviously still unlock the car remotely.

InTheDark, I assume that by asking "I'm not sure why people think there's any advantage to a manual," you mean an advantage specific to this situation (as there are multiple advantages in general to driving a manual). It is true that you can put an automatic in neutral, but with a manual you have the clutch also, which physically severs the connection between the engine and the wheels without any computer involvement. Some of the automatic transmissions now are so complicated and automated (especially the ones in the hybrids like the Prius, which have to manage 2 motors) that I honestly don't know if they are failure safe the way a manual transmission is, being purely mechanical. Also, it is a lot harder to stall an automatic since the engine is not directly linked to the wheels.
Completely hypothetically, if a car with a manual transmission was experiencing "runaway acceleration," you could put the car into neutral and slow it down to a stop. If for some strange reason the push button start will not turn off the car, you can always just put it in your highest gear and just drop the clutch and stall the car. I have absolutely no idea why all of these things would go wrong at once.

 

[smflorkey]

On a separate note, why the hell do you have to add a letter "k" when using adjective form of panic?

Because English phonics, irregular as they are, fairly regularly change the sound of "c" when it is followed by "e" or "i". When you add "ed" to "panic" regular English phonics would want that to sound like "panised" -- probably not what you wanted to say. To prevent this incorrect pronunciation the convention is to add "k" (or in the case of "picnic" to just change the final "c" to a "k"). That's what happens when a language borrows bits from half the other languages on the planet.

 

[smflorkey]

Accumulated speed combined with powerful engines equals boiling brake fluid and no brakes.

I don't see where speed or high braking effort leads to boiling brake fluid. The pressure of the panic stop would greatly reduce any fluid's ability to boil. What am I missing? :shrug:

You may be correct here. I was just doing some math.

I like math! Thanks for bringing a little objective science to the discussion. I also agree with your conclusion. :thumbsup:

Yes, I now tend to believe they just gave up, perhaps because the brakes weren't as effective due to the combination of conditions. Nevertheless, this is still a dangerous problem meriting correction. If a 19 year CHP veteran has trouble controlling a vehicle, you can bet the average driver will be utterly helpless.

Agreed on all points!

I don't understand why the brakes of the Lexus would be "on fire."

I don't remember the source of that quote, but my guess is it was a news reporter. We need to remember that news is entertainment selling advertising time. The more sensational the report, the more eyeballs the station can sell to advertisers. :thumbsdow They want us to believe they know what they're saying...

I have a really dumb question, but if I had a "runaway car" couldn't you put it in neutral (or manual transmission out of gear)? Then it seems the brakes should stop it even if the engine is running to beat the band.

As has been stated by at least two others, this is a supremely logical idea. The only potential fly in the ointment is whether the Prius' (or this Lexus') electric motor goes through the transmission or is more directly coupled to the drive axle. Some purely electric cars have the drive motors mounted on each wheel. This seems awkward (at best) for a hybrid. Does anyone know how these hybrid drivetrains work?

Ctrl-Alt-Del

 

[alpg88]

i have 2 cars with drive by wire, never had a problem.
there is also such thing in all cars, as emergency brake, the trick is to apply it gradually, or you'll spin out of control.
e brakes are mechanical, and any electronic or engine failure doesn't affect them

 

[turbodog]

i have 2 cars with drive by wire, never had a problem.
there is also such thing in all cars, as emergency brake, the trick is to apply it gradually, or you'll spin out of control.
e brakes are mechanical, and any electronic or engine failure doesn't affect them

The e-brake uses the same pads/rotors are the normal brakes. If normal brakes are overheated, then the e-brake does not work either. Most e-brakes don't have the same stopping power as normal brakes either.

 

[turbodog]

I don't see where speed or high braking effort leads to boiling brake fluid. The pressure of the panic stop would greatly reduce any fluid's ability to boil. What am I missing?...

You're missing that prolonged braking from a high rate of speed leads to a massive amount of heat produced. It has to go somewhere, and will eventually overheat the brake fluid.

 

[alpg88]

The e-brake uses the same pads/rotors are the normal brakes. If normal brakes are overheated, then the e-brake does not work either. Most e-brakes don't have the same stopping power as normal brakes either.

e brakes only hooked to rear wheels, most of the braking done with regular brakes are front wheels, never seen e brakes work with front wheels, all e brakes don't have same stopping power as normal brakes, but it is better than nothing, no?

 

[oronocova]

Some Subarus had/have the parking brake connected to the front.

I drive a 07 Civic for work. It's a stick and the drive-by-wire throttle sucks. There is a lag between pushing the pedal and the engine accelerating. The dealer says they can re-learn it for 40 bucks. Why not just make it work in the first place? Plus it's not my car so I really don't care.

My wife's car is a 07 Camry also DBW throttle. It has some smart features like downshifting while in cruise control if you go over 5mph over you set speed. In 40k miles she nor I have ever had a problem with the throttle not responding as expected. Sometimes the transmission will "flare" which has been reported on some of the Toyota forums. Ours does it maybe once every thousand miles so I'm not too worried. Basically on a upshift at mild throttle the transmission acts like speed shifting a manual transmission. (There will be a time out of gear with the engine revving before the shift actually happens.)

One other thing, and I may be wrong so correct me. But haven't most big trucks/road tractors used an electrical throttle linkage for quite some time. And if that is the case, I really want to know why can't Honda make their throttle work right

 

[alpg88]

Some Subarus had/have the parking brake connected to the front.

i actually had to google that subaru, since i,ve never worked on loyale, but yes you are right, however they are not powered by vacuum booster, it is purely mechanical linkage.

 

[Patriot]

The e-brake uses the same pads/rotors are the normal brakes. If normal brakes are overheated, then the e-brake does not work either. Most e-brakes don't have the same stopping power as normal brakes either.

There may be rare exceptions but in most vehicles the e-brake or park brake system is purely mechanical and uses its own specific set of brake brake "shoes." Typically they will only ever have to be replaced if the driver accidentally leaves them partially engaged without realizing that they're dragging. Depending on the car the amount of force they can apply is limited although most are capable of locking the rear wheels with a sharp job on the handle or pedal.

You're missing that prolonged braking from a high rate of speed leads to a massive amount of heat produced. It has to go somewhere, and will eventually overheat the brake fluid.

That's true but we're talking about one emergency stop, not repeated hard brakings that you'd experience on a race track or something. The average Sedans sedan's brake fade due to high pad temperatures long before hot brake fluid temperatures rise. Not really a factor here, even from high speed.

 

[Illum]

not to open a new can of worms here...but, purely from a emergency standpoint what is the effectiveness of the parking brake to stop a car? :duck:

 

[Mjolnir]

Well you will likely lose stability, and it likely won't end well at highway speeds, especially if the brakes lock the front wheels.

 

[Patriot]

Just guessing but I would be surprised if a mechanical pull or push lever could look the fronts on a front ebrake vehicle. The weight transfer to the front causes enormous traction loads and resistance to stoppage. With rear ebrake the load is transferred off of the rear tires effectively reducing traction and making them easier to lock. As long as you do this in a relatively straight line the stability is pretty good even when fully locked.

Most manufacturers now refer to it as a park brake rather than an emergency brake. You can imagine that lawyers had something to do with that. In any case they'll stop the car without too much trouble. If you give yourself about twice the braking distance that's usually enough. If the engine is pulling against them though....forget it, they can't overcome the engine's torque. Yes, I've horsed around a lot being in the car business for so long.

 

[Mjolnir]

Wait a second, why doesn't the driver just jettison the warp nacelles? That should stop the vehicle.

 

[LuxLuthor]

Wait a second, why doesn't the driver just jettison the warp nacelles? That should stop the vehicle.

The newer models abandoned the flaky hyperdrive, plus as Star Wars fans, they are unable to understand the more practical Star Trek technology.

 

[Juggernaut]

The newer models abandoned the flaky hyperdrive, plus as Star Wars fans, they are unable to understand the more practical Star Trek technology.

Oh, I normally just drop in all the cooling rods, that usually stops any runaways in the 74's Lincoln's nuclear reactor.

Back on topic, can't you guys wait until Drive by wire steering and brakes come out:duck:?