Snoozin' and crusin' in the rain

Have any of you seem this e-mail warning thing?

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A 36 year old female had an accident several weeks ago and totaled her car. It was raining, though not excessively, 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 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 when your car begins to hydroplane and your tires lose contact with the pavement, your car will accelerate to a higher rate of speed making you take off like an airplane.

She told the patrolman that was exactly what had occurred.

The patrolman said this warning should be listed on the driver's seat sun-visor - NEVER USE THE CRUISE CONTROL WHEN THE PAVEMENT IS WET OR ICY - along with the airbag warning. We tell our teenagers to set the cruise control and drive at a safe speed - but we don't tell them to 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 a similar accident,totaled his car and sustained severe injuries.
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Great story! Apart from the mis-use of the A-word.

But it is completely false.

Urban myth.

Cannot happen.

The laws of physics always apply.

If your tires lose contact with the pavement, how can the car accelerate? Let alone fast enough to send the car "flying through the air"?

No possible way.

When the car hydroplanes - when the tires lose contact with the pavement - and throttle is maintained (as with cruise control, or even if you are still driving the car with your own right foot) the driving wheels will just spin. Unless of course someone strapped a rocket engine to your rear bumper and forgot to tell you.

Now, IF while your driving wheels are spinning they should happen to encounter a bit of dry pavement, they will try to accelerate the car. But the throttle opening will be so small that it would never generate enough acceleration to give the car anything more than a gentle jerk. I mean, if you're on dry pavement at highway speed and slam the accelerator to the floor - i.e., wide-open throttle - does your car take off "like an airplane"?

Not even if you're in a Porsche 911 Turbo.

Now, it ISN'T wise to drive with snooze 'n' cruise in the rain, but not because of this. It just can catch you a bit off-guard.

If the car hydroplanes and the driver loses control of the car (although a case can be made that with cruise control at any time the driver has abandoned control of the car...) you will sense it by a loss of feel at the steering. Lift your right foot gently off the accelerator, DO NOT BRAKE, look in the direction you want to go (i.e., aim for a gap in the traffic pattern, or at worst the thinnest tree or the shallowest ditch) and steer that way. Assuming you weren't going stupidly fast in the first place, you should regain control of the car before you hit something.

If this sounds like what you were taught to do in a skid on snow or ice, move to the head of the class. It is exactly the same thing.

Comments

[Rick Clayton]

The instruction to "lift your right foot gently off the accelerator" is appropriate only for an automatic transmission vehicle with the cruise control off. If the cruise is on, it will attempt to keep the drive wheels rotating at its set speed. Lifting the foot will do nothing (it probably isn't there to start with due to the cruise control being on). Another approach is to shift to neutral (automatic) or depress the clutch pedal (manual) and lift off the throttle. These actions cancel the cruise control and allow the drive wheels to regain contact with the road in an undriven and unbraked way, which will maximize the ability to regain control of the skid. Once directional control is re-established, threshold braking can be used to slow the vehicle.

[Jim Kenzie]

To Rick:

RE: Instructions if you hydroplane.

You're right. I was assuming that if the car's wheels had started to spin the cruise would already have kicked itself off, and IF your foot was on the gas, get it off!

If cruise is still on it has to be deactivated too; in most cars, your suggestions will do that trick.

Slipping the car into neutral and depressing the clutch (in a manual) are indeed the right things to do. The idea is to allow whatever grip the tires do have to be directed towards steering the car, not accelerating or braking it, even by engine braking.

Thanks for your more complete description!

Jim Kenzie

[John McKinlay]

Jim,

How come you're one of the only journalists who consistently use common sense and write about the truth? I'm surprised some of these lobbyists haven't had you shut down yet.

Keep it up!

- john.

[Jim Kenzie]

Hi John:

Wanna be my agent?

Thanks!

Jim Kenzie

[Rick Clayton]

There is a warning against using the cruise control when the road is wet or icy the owner's manual of just about every car. It is too bad that these things are rarely read.

[Don]

Great advice as usual. It seems to me that if the car begins to hydroplane while on cruise control the drive wheels will spin faster. That signals the cruise control to release the throttle to maintain speed. This occurs faster than you or I could react as it takes only a minuscule variation in speed for most cruise controls to react. This is not intended to be an argument for using cruise control in the rain but it seems to suggest that the car simply could not accelerate while on cruise in this situation.