Cruise Control and Foul Weather DO NOT MIX

[LoudMusic]

Disclaimer: Everyone here knows I'm neurotic anyway. So that explains my reply to the following ...


Something I received in an email at work

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This makes a great deal of sense when you think about it!

Interesting- Re: Hydroplaning

A 36 year old female had an accident several weeks ago and totaled her car. A resident of Kilgore, Texas, she was traveling between Gladewater & Kilgore. It was raining, though not excessive, when her car suddenly began to hydroplane and literally flew through the air. She was not seriously injured but very stunned at the sudden occurrence!

When she explained to the highway patrolman what had happened he told her something that every driver should know -NEVER DRIVE IN THE RAIN WITH YOUR CRUISE CONTROL ON. She had thought she was being cautious by setting the cruise control and maintaining a safe consistent speed in the rain.

But the highway patrolman told her that if the cruise control is on and your car begins to hydroplane -- when your tires loose contact with the pavement your car will accelerate to a higher rate of speed and you take off like an airplane. She told the patrolman that was exactly what had occurred. We all know you have little or no control over a car when it begins to hydroplane. You are at the mercy of the Good Lord. The highway patrol estimated her car was actually traveling through the air at 10 to 15 miles per hour faster than the speed set on the cruise control.

The patrolman said! this warning should be listed, on the drivers seat sun-visor - NEVER USE THE CRUISE CONTROL WHEN THE PAVEMENT IS WET OR ICY, along with the airbag warning. Use the cruise control only when the pavement is dry.

The only person the accident victim found, who knew this (besides the patrolman), was a man who had had a similar accident, totaled his car and sustained severe injuries. If you send this to 15 people and only one of them doesn't know about this, then it was all worth it. You might have saved a life.
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So I read all that and thought, "Yup, you'd have to be pretty stupid to cruise control it in the wet." So then I typed up the following email and sent it to the same people who received the first one.

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Where I agree that driving with cruise control in foul weather is a bad idea, I disagree with the majority of what they're saying from a scientific point of view. And their repeat references to "the patrolman said!" are annoying.

"her car suddenly began to hydroplane and literally flew through the air"

I believe she had the perception of it flying through the air probably because she had never hydroplaned before - it is an eerie feeling. I don't believe a car would go airborne from hydroplaning unless it hit something or left the road into a ditch or off a hill.

"when your tires loose contact with the pavement your car will accelerate to a higher rate of speed and you take off like an airplane"

What is actually happening is your car is slowing down due to lack of traction, but the cruise control is trying to keep you moving at the preset speed. The car gets speed information from one set of tires, but delivers speed through the other set. One set slows down but your drive wheels deliver more power. You don't actually speed up at all, but you do completely loose traction on your drive wheels, and in most cases your drive wheels are your front wheels where you steer the car.

"The highway patrol estimated her car was actually traveling through the air at 10 to 15 miles per hour faster than the speed set on the cruise control"

Anyone care to explain to me how a car with no traction can increase speed? The race car guys would love to see how this works. And again, I don't believe a one and a half ton car is going to leap into the air because it got its feet a little wet. Though hydroplaning may give you that perception.

I think the single biggest argument here is that when you're using the cruise control you're by definition not as involved in the control of the car. So get involved, save your own skin. Don't rely on an automobile engineer you've never met (:

What they need to do to improve cruise control is to add a feature that causes the system to shut off if it is delivering more power and making no change in the speed of the car. It is also possible to put water detectors under the car, which could be used in conjunction with other safety features.

SOURCE: http://www.snopes.com/autos/techno/wetroad.asp

My explinations and assumptions could be a little off, but I believe I am generally correct on my points.
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The internet is a great place to share information, but I think more people need to take the time to validate information before they send it on to the masses. It's like what someone has in their signature, "If you don't know the answer, don't give the answer". Words to live by.

 

[TB]

Living in ND, you learn those kinds of things mighty quick in the winter. Or you live at the local friendly body shop. Your call.

Edit: Don't some/most new cars have a sensor that detects wheel spin and disengages the cruise?

 

[LoudMusic]

Ha ha, yeah (:

I am of the firm belief that everyone should be required to take higher level driving courses in order to be licensed to drive in their area. Obviously southern Californians don't need to know how to drive on icey roads, but North Dakotans most certainly do. Even in Arkansas we get some bad weather. I think everyone needs to know how to drive on wet roads and how their car will act on wet roads. Perhaps in addition to the driving courses for your license you should also be required to take your car on an all inclusive driving course to test your ability in the common inclimate situations for your location. And if you get a new car you would be required to drive it on the course before it can be insured.

Wow, the things I'm going to do when I'm president ....

 

[LoudMusic]

Living in ND, you learn those kinds of things mighty quick in the winter. Or you live at the local friendly body shop. Your call.

Edit: Don't some/most new cars have a sensor that detects wheel spin and disengages the cruise?

Honestly I don't know. I do know that there are all kinds of "smart all-wheel drive" setups that distribute power where it needs to be, but I think in a hydroplaning situation that would work to a dissadvantage.

 

[skip0110]

"her car suddenly began to hydroplane and literally flew through the air"

I believe she had the perception of it flying through the air probably because she had never hydroplaned before - it is an eerie feeling. I don't believe a car would go airborne from hydroplaning unless it hit something or left the road into a ditch or off a hill.

I think this was meant to be hyperbole. Cars weigh a heck of a lot; they dont just tend to fly off the road.

"when your tires loose contact with the pavement your car will accelerate to a higher rate of speed and you take off like an airplane"

What is actually happening is your car is slowing down due to lack of traction, but the cruise control is trying to keep you moving at the preset speed. The car gets speed information from one set of tires, but delivers speed through the other set. One set slows down but your drive wheels deliver more power. You don't actually speed up at all, but you do completely loose traction on your drive wheels, and in most cases your drive wheels are your front wheels where you steer the car.

The cruise control sensor is detecting wheel speed, which would actually increase with a loss of traction at constant throttle, since there would be less load on the engine. As I understand, the cruise control is using the same signal as the speedometer, which comes form the drive wheels. So the cruise control would cut throttle somewhat as the freespinning wheels begin hydroplaning. Not enough to prevent a crash, mind you, but somewhat nonetheless. (Probably what happens in these situations, is not that the cruise control "slams" the car into a tree, but that a panicking driver gives some sort of sudden contol input that upsets the car.)

"The highway patrol estimated her car was actually traveling through the air at 10 to 15 miles per hour faster than the speed set on the cruise control"

Anyone care to explain to me how a car with no traction can increase speed?

If the car was going downhill when the loss of traction occured. Cruise control will not apply the brakes except in very fancy Mercs/Lexi with the adaptive kind.

I think the single biggest argument here is that when you're using the cruise control you're by definition not as involved in the control of the car. So get involved, save your own skin.

👍

What they need to do to improve cruise control is to add a feature that causes the system to shut off if it is delivering more power and making no change in the speed of the car.

How? The only way for the car to detect road speed is by the rotation of the wheels/drivetrain. Although I do have an idea--on cars with navigation, the doppler shift of the GPS signals can be used to determine speed relative to the earth. (And your idea of a "water sensor" is dodgy at best.)

 

[TB]

And why, I ask, should Cali-forn-ians be excluded from this law, Mr. President? Because then they come to ND, hit me and I end up in the aforementioned body shop.

President Loudmuic. And to think that I knew him when he was just a putz on GTP.

 

[LoudMusic]

I think this was meant to be hyperbole. Cars weigh a heck of a lot; they dont just tend to fly off the road.

Possibly, but it was mentioned twice with referance to "taking off like an airplane", so I went with literal. It gave me more to ***** about so it worked in my favor (:

The cruise control sensor is detecting wheel speed, which would actually increase with a loss of traction at constant throttle, since there would be less load on the engine. As I understand, the cruise control is using the same signal as the speedometer, which comes form the drive wheels. So the cruise control would cut throttle somewhat as the freespinning wheels begin hydroplaning. Not enough to prevent a crash, mind you, but somewhat nonetheless. (Probably what happens in these situations, is not that the cruise control "slams" the car into a tree, but that a panicking driver gives some sort of sudden contol input that upsets the car.)

It is my understanding that the speedometer takes speed from an unpowered wheel, which should slow down as the vehicle looses traction. Though I suppose it could be different for all models. But yes I would concur that it's a rare occation that the driver is not at fault.

If the car was going downhill when the loss of traction occured. Cruise control will not apply the brakes except in very fancy Mercs/Lexi with the adaptive kind.

Hmmm, yes. Downhill. That would be the obvious answer that completely escaped me

How? The only way for the car to detect road speed is by the rotation of the wheels/drivetrain. Although I do have an idea--on cars with navigation, the doppler shift of the GPS signals can be used to determine speed relative to the earth. (And your idea of a "water sensor" is dodgy at best.)

I believe you could detect the speed of the car with a downward facing speed radar. It could even be very low powered since it wouldn't have to be checking more than a foot or so away. Keeping it clean would be the difficult part. Wheel spin is the only obvious option and that can be done by putting sensors on multiple wheels - some powered some not. I do not believe GPS has a quick enough response time, though rental companies are using it to track their cars and the speeds they are traveling. Also, "water sensors" are used to engage the windshield wipers on some cars, aren't they? Or do they use some other form of technology? Detecting water on a surface can easily be done with current technology.

And why, I ask, should Cali-forn-ians be excluded from this law, Mr. President? Because then they come to ND, hit me and I end up in the aforementioned body shop.

President Loudmuic. And to think that I knew him when he was just a putz on GTP.

Well, you can't require someone to take a test if you can't prove that they're going to need it. Perhaps there could be an interstate licensing system as well.

An answer for everything ... I'd make a GREAT president.

 

[TB]

Well, you can't require someone to take a test if you can't prove that they're going to need it.

That was my entire Spanish class in high school. Prove that at some point in my life I'm going to need to conjugate 'soy'. You can't do it. But they still made me learn it. Soy, Eres, Es, Somos, Sois and Son

 

[skip0110]

It is my understanding that the speedometer takes speed from an unpowered wheel, which should slow down as the vehicle looses traction. Though I suppose it could be different for all models.

As far as I know, all Ford/GM speedometers are powered by a little plastic gear in the transmission. For mechanical speedometers, this gear directly spins the cable that drives the speedo. For electric gauges, there is a small circuit sitting on the tranny that converts the spinning to electric pulses. And in both my Civics, wheel speed is indicated. However, now I guess it might be easier for designers to simply pull a signal from an ABS sensor than toget it from the transmission.

I believe you could detect the speed of the car with a downward facing speed radar. It could even be very low powered since it wouldn't have to be checking more than a foot or so away. Keeping it clean would be the difficult part. Wheel spin is the only obvious option and that can be done by putting sensors on multiple wheels - some powered some not. I do not believe GPS has a quick enough response time, though rental companies are using it to track their cars and the speeds they are traveling.

The radar idea is good, and manufacturers have some experience with it too from adaptive cruise control.

GPS has a resolution of 3-5 m. But it's just some sort of electromagnetic signal of a known frequency, so if the car is moving, it will cause a doppler shift in the signal, from which the car's speed can be determined. It's how magazines come up with their 0-60 times and 1/4 mile trap speeds--here is an example of a commercially available product.

EDIT: In fact, it turns out they make something that would be perfect for this application--a little box the outputs a digital speed signal. Automakers could just use the GPSTran or CANTran.

Also, "water sensors" are used to engage the windshield wipers on some cars, aren't they? Or do they use some other form of technology? Detecting water on a surface can easily be done with current technology.

Ah, you're right. I guess there are high-reliability water sensors.

 

[Small_Fryz]

very interesting indeed, you just have to be "careful and mindful" when driving in poor road conditions. And you have to know what to do if you get into certain situations.

 

[daan]

How bald were her tyres if she aquaplaned during "non excessive" rain? I have never aquaplaned in my puff, and I live in Scotland where it's been known to rain on occassion....

 

[CFM]

As far as I know, all Ford/GM speedometers are powered by a little plastic gear in the transmission. For mechanical speedometers, this gear directly spins the cable that drives the speedo. For electric gauges, there is a small circuit sitting on the tranny that converts the spinning to electric pulses. And in both my Civics, wheel speed is indicated. However, now I guess it might be easier for designers to simply pull a signal from an ABS sensor than toget it from the transmission.

I'm pretty sure most cars still use the gear in the transmission, because on the assembly line cars with different size wheels and different final drive ratios will use a different gear, which can be slapped in quickly during assembly. This allows the sensor (or cable) running the spedometer to remian the same across all versions of the same car, regardless of wheel/tire size and gear ratios. Speedometers aren't very accurate anyway, most manufacturers allow 5-10% variance from actual speed. At low speeds, you will be close but at high speeds you can be way off. End of spam

 

[Anderton Prime]

Ha ha, yeah (:

I am of the firm belief that everyone should be required to take higher level driving courses in order to be licensed to drive in their area. Obviously southern Californians don't need to know how to drive on icey roads, but North Dakotans most certainly do. Even in Arkansas we get some bad weather. I think everyone needs to know how to drive on wet roads and how their car will act on wet roads. Perhaps in addition to the driving courses for your license you should also be required to take your car on an all inclusive driving course to test your ability in the common inclimate situations for your location. And if you get a new car you would be required to drive it on the course before it can be insured.

Wow, the things I'm going to do when I'm president ....

What about when a Californian takes a drive to Michigan to visit relatives in the dead of winter? They'll have even less training than a permanent resident of Michigan. Your plan will never work.

 

[McLaren]

I picked some of those out what you already talked about. I don't believe your car is just gonna take off into the air all of sudden if it loses traction.

I'd love to hear how the car does that.

 

[///M-Spec]

Good thing almost all cars now sold with cruise control also come with traction control optional or standard.

But I have a hard time imagining a situation where a car may hydroplane with the cruise on, but not with the cruise off. There is something else wrong in this scenario: excessive speed for weather condition or inadequate tire tread or tire inflation.

I can see where cruise making a situation slightly harder to recover, but never cause a hydroplane situation.


M

 

[Duke]

Exactly. Too fast is too fast, whether it's a foot or a servo on the throttle. It's not the cruise control's fault.

Speed sensors measure the revolutions of the output shaft of the transmission, either mechanically in older cars or electronically in newer cars. This is used to calculate the assumed speed of the car based on the stock wheel/tire circumference. This is why a car coasting in neutral still indicates speed on the instruments.

If one wheel is spinning, the output shaft is spinning faster than ground speed, and the indicated speed is much higher than actual. In all cases, this would cause the cruise control to back off the throttle until wheel speed fell below the set point. It would never cause the engine to race out of control.

 

[LoudMusic]

What about when a Californian takes a drive to Michigan to visit relatives in the dead of winter? They'll have even less training than a permanent resident of Michigan. Your plan will never work.

I had already answered this in a later post.

Well, you can't require someone to take a test if you can't prove that they're going to need it. Perhaps there could be an interstate licensing system as well.

In addition to that, Californians visiting Michigan in the dead of winter should know better anyway. And to say Your plan will never work is just assinine.

 

[Pupik]

If the car was going downhill when the loss of traction occured. Cruise control will not apply the brakes except in very fancy Mercs/Lexi with the adaptive kind.

We still don't recommend using the cruise control in any sort of dodgy weather, nor if you're travelling on a very curvy road, since cruise control is rather inconsistent at times.

In any case, when I received my second driver's lesson from my dad, we drove on the highway (it was fairly deserted at the time), and he explained the best way to drive on a limited-access road.

He explained how to and when to use cruise control: "When going in a straight line, not much, if any traffic, and when you're fully paying attention. don't use cruise control because you don't feel like paying attention to the road..."

Words to remember. I've never liked using the cruise control feature for more than a moment or so (if you you have to scratch your foot or leg, for example)...I feel "disconnected" from the car.

 

[LoudMusic]

I use it on loooonnnngg drives. Like the 10 hour drive from Little Rock to San Antonio. Set the cruise control at 70 and watch the trees go by.

Sometimes I use it during my 35 mile commute to avoid getting speeding tickets. Set it at the limit and hop in the right lane. The problem with that is there are usually a lot of people on the road. I can only use the CC when I work late and am going home around 7 or 8 o'clock.

 

[cardude2004]

People use it in Wisconsin's bad weather and cause a lot of accidents when we have snow and stuff. People don't realize that it senses wheel slipping. They think it is set for 65 and it was stay at the same wheel rotation at all times and never increase if the wheel starts to slip.

 

[Famine]

People use it in Wisconsin's bad weather and cause a lot of accidents when we have snow and stuff. People don't realize that it senses wheel slipping. They think it is set for 65 and it was stay at the same wheel rotation at all times and never increase if the wheel starts to slip.

What would happen if you put a car on a rolling road and used the Cruise Control then?

Cruise Control isn't something manufacturers tend to fit, even on luxo-barges, for the UK market. We just don't have enough straight or empty roads.

 

[LoudMusic]

What would happen if you put a car on a rolling road and used the Cruise Control then?

Cruise Control isn't something manufacturers tend to fit, even on luxo-barges, for the UK market. We just don't have enough straight or empty roads.

Yeah I've wondered about that. Jeremy Clarkson had it in the S8 Diesel he drove 400+ miles in, but didn't use it because it killed his mpg.

I've driven roads that were 400 miles of nearly dead straight. How about 1400 miles from Los Angeles to Oklahoma City with just a wiggle in the middle when you cross the mountains?

 

[Famine]

Rich Hall - famous American comedian (to us Brits) - was saying that in the US, some east-west roads are so straight for so long that they have to incorporate the odd twist to the north to allow for the curvature of the Earth.

 

[cardude2004]

What would happen if you put a car on a rolling road and used the Cruise Control then?

Cruise Control isn't something manufacturers tend to fit, even on luxo-barges, for the UK market. We just don't have enough straight or empty roads.

Most of our roads are hilly and curving because most of them follow old Native American trails. Cruise control works fine on them, as long as it isn't raining or snowing. Most cars have cruise control on them, unless they are manuals, here in the US. Most manual vehicles you have to get cruise control separate.

 

[Famine]

Errr... "Rolling Road" does not mean "road over hills".

 

[cardude2004]

Ok, then what do you mean?

 

[skip0110]

I think Famine means something like a dyno. Such as they use for emissions testing.

 

[Famine]

A Rolling Road.

 

[cardude2004]

Oh, I see. I don't thik it would effect cruise control to put your car on a rolling road.

 

[LoudMusic]

Errr... "Rolling Road" does not mean "road over hills".

Actually I can see how he might mistake "rolling road" for "road on rolling hills", which would be like a wavey road.