Don’t Use Cruise Control In The Rain

Status: Hoax
Here's an email that's been circulating around:
"A 36-year-old female had an accident several weeks ago and wrote off her vehicle. It was raining, though not excessively, when her car suddenly began to aquaplane and literally flew through the air. She was not seriously injured but very stunned at the sudden occurrence. When she explained what had happened to a highway patrolman, he told her she should never drive in the rain with cruise control activated. If your car begins to aquaplane, it will accelerate beyond the set cruise control speed when the tyres lose contact with the asphalt."

So is there any truth to this? Is it dangerous to drive in the rain with cruise control activated? Not according to Australia's RAA (Royal Automobile Association) which recently issued an advisory about this email:

“Should the car’s tyres break traction with the road, such as in an aquaplane situation, the increase in wheel speed would be sensed and the cruise control system would then reduce the amount of throttle and maintain the set speed. Additionally, cruise control systems are deactivated as soon as the brake is applied. As braking is usually an automatic reaction in most emergency situations, the scenario of cruise control causing an increase in vehicle speed is highly unlikely.”

I actually never use cruise control, whether or not it's raining, because I have a bit of a phobia about it. I have a fear that one time I'll step on the brake, and the cruise control won't deactivate.

Email Hoaxes

Posted on Thu Apr 13, 2006


In both of my vehicles that have cruise control, the manuals say not to use it when the roads are wet. I think that the companies include such warnings more to cover themselves against lawsuits in the event of an accident, rather than due to any major danger.

I use cruise control on wet roads often enough, as long as the visibility is good and the traffic's not too heavy.
Posted by Accipiter  on  Thu Apr 13, 2006  at  10:39 AM
Hydroplane, not aquaplane. Aquaplaning is kneeboarding behind a motorboat.
Posted by Marc  on  Thu Apr 13, 2006  at  11:14 AM
Well, if the CC didn't deactivate, couldn't you just throw the car in neutral?
Posted by joemono  on  Thu Apr 13, 2006  at  12:23 PM
This is more or less true. You should NOT use cruise control in slippery conditions (rain or snow and ice). The problem is if the vehicle slows down, say for a hill, the CC will detect the slower speed and of course activate the accelerator. If the vehicle doesn't get up to the set speed soon, then the CC will give it even more gas. If it does this and at the same time the transmission down-shifts it will cause the tires to spin. This usually makes the back end of the vehicle swerve (with rear-wheel drive anyway) to one side due to torque. At this point you can easily lose control.

I think most car spedometers (and hence the CC) get their speed indication from the transmission. You can see this by watching the indicated speed increase when stuck in snow or mud. One would think the CC would see the same thing in the scenerio above and try to reduce speed but it would all depends on the reaction time of your CC. Before that happens you could be in the ditch.

Of course, all this is much more likely to be a problem on ice but I could see it being a problem in heavy rain too.
Posted by Captain Al  on  Thu Apr 13, 2006  at  01:23 PM
The cruise control would never accelerate beyond the set speed, outside of catastrophic failure. The car's speeed is determined by how fast the tires rotate. It makes no difference if that car is driving on the road or up on jacks, the cruise control will keep the tires spinning at the same rate.

I think the confusion comes from the fact that, should your tires lose traction with the ground while your foot is on the accelerator, your tires will start spinning faster. Your accelerator governs how much power your engine is providing to your drive train, now how fast you're going. That's why you need to press down farther when going up a hill to maintain the same speed. In fact, a cruise control might even react faster than you in easing acceleration in the event you started hydroplaning.

However, unless it was more advanced than the systems I've used, it would not stop the acceleration. It would just try to keep the tires spinning at the same rate, making it moderately more dangerous than controlling it yourself. A person would pull their foot off the accelerator first, then either brake or try to keep control until the tires reconnect. Cruise control would keep acceleration up, but your speed would drop off making it harder for your tires to reconnect with the pavement.

I have used CC in the rain, but I admit I'm taking a risk with it.
Posted by Charybdis  on  Thu Apr 13, 2006  at  01:30 PM
Charybdis wrote:

"However, unless it was more advanced than the systems I've used, it would not stop the acceleration. It would just try to keep the tires spinning at the same rate, making it moderately more dangerous than controlling it yourself. A person would pull their foot off the accelerator first, then either brake or try to keep control until the tires reconnect. Cruise control would keep acceleration up, but your speed would drop off making it harder for your tires to reconnect with the pavement."

You have made a couple of mistakes in who cruise control works. First, if the cruise control is on, the driver *does not have their foot on the accelerator*. That's the entire point of cruise control. Second, when the driver hits the brakes, the cruise control turns off. This is true of *all* cruise controls.
Posted by Terry Austin  on  Thu Apr 13, 2006  at  05:21 PM
Ya know, when I was a truck driver, I heard all the BS about cruise control, anti-lock brakes, AND engine brakes (JAKE Brakes) and how NONE of these features should ever be used in adverse weather conditions. Now I am SURE there are a gazillion drivers who who tell of stories of how they, or someone they know, had a wreck cause they didn't listen to the rumors. I'm here to tell you, that I have TRIED to make the rumors true in adverse weather conditions and empty drop lots... no matter what I tried, I just couldn't make these safety features do what they weren't designed to do.
Posted by Christopher in Joplin, Missouri  on  Fri Apr 14, 2006  at  05:01 AM
Terry, I never said that a driver would be accelerating while using cruise control. I was showing the difference between CC and manual control at the moment you start hydroplaning.

I'm also well aware that braking disengages CC, but a drive manually accelerating will take his foot off the accelerator slightly sooner than he could disengage cruise control by braking. It's clearly a more dangerous situation to use CC on wet roads, but it probably needs study to determine just how much more dangerous it is.

I'm sorry I didn't make myself clearer in my first posting.
Posted by Charybdis  on  Fri Apr 14, 2006  at  08:57 AM
Like Christopher, I've done a lot of cross-country driving, although I've done it in various cars rather than trucks. (You haven't lived until you've driven the PCH in a rental car during a thunderstorm.)

When you're driving nine or more hours at a stretch, on a tight schedule, CC is not optional -- it's a necessity.

Here's the no-brainer: During adverse weather conditions, you set your speed lower. Going 70 MPH in a blizzard is going to be trouble whether you have CC engaged or not.

And thank you for being a trucker, Christopher. I can't count how many times I've driven across North Dakota with about zero-percent visibility. I just pick a Semi and follow it at a respectful distance.
Posted by SicTim  on  Fri Apr 14, 2006  at  09:39 AM
I'm not sure why it happens, but I have a 2002 Sierra 4wd, and if I have it in 2-hi and not the auto 4wd, it will lose traction and the rear will slide out in heavy rain using the CC.
Posted by MItch  on  Fri Apr 14, 2006  at  06:31 PM
I've been driving a lot with CC on rainy conditions, and on some bad roads, and even when just one of the wheel (front weel drive) hit a poodle of water and started spinning, the speed indicator would go up in a flash, and the CC would not only "hold it" until the speed gets down but plainly disengage. I had to reset it. And I'm not talking about a fancy BMW with all the latest auto-electro-matic gizmos, but about a 1988 Ford Taurus Station Wagon... So I would assume that the "new" cruise controls have this feature too.
Posted by Pierre  on  Sun Apr 16, 2006  at  08:47 PM
My understanding about the advice is that when using the cruise control many drivers tend to relax more and pay less attention to the road. Just my two cents.

Oh and Alex I had an experience with cruise control that definitely made me leary of them. I had recently purchase a used car with cruise control. When I tried to engage it nothing happened, until about 15 mins later, suddenly the car decided to accelerate. Thinking is was just coincidence I tested it again, same results. It left me not trusting cruise control.
Posted by Myst  on  Mon Apr 17, 2006  at  01:11 PM
The person who wrote the following must be an American:

Hydroplane, not aquaplane. Aquaplaning is kneeboarding behind a motorboat.
Posted by Marc on Thu Apr 13, 2006 at 09:14 AM

Aquaplaning is the British word for Hydroplaning.
Posted by Joe  on  Wed May 03, 2006  at  07:45 AM
:coolsmile: Many of you folks know a lot about cruise control systems, so maybe someone has heard about this.

I have been told that a late 90's BMW model has had a serious problem with the cruise control wiring and some cars have surged forward and increased accelerating until the driver shut off the key (thereby losing their power steering) or often the car crashed into something.

The drivers stated that when they pressed on the brake, it just accelerated faster and faster (due to the short). Most said that it was going 70 or 80 or 90 by the time it crashed.

Even though mechanics have proven that the wires or insulation shorted out, the BMW experts deny that the car has a flaw. BMW blames it on driver error. It seems strange that these people all have the same story and their mechanic find a problem but BMW does not. Many people have been killed, so no wonder that BMW denies any liability.

I have driven many cars with CC and had no problems except with a 1985 Firebird. In that case, the car was about 2 years old and the CC was often left engaged by my teenagers but not set. Eventually, the CC simply activated itself without the driver knowing it until the car surged ahead, without notice. I can understand about the guy who bought a used car and it sounds as if it did the same thing. After the problem with the Firebird. I told my family members to never turn the CC on again, as it was unreliable.

I am interested in purchasing a BMW but there seems to be so much "hush - hush" by BMW that I am not uncertain if the CC problem is universal or just one model and which model is in question.

Does any body know anything about this?

Thanks a million!
Posted by bnhs  on  Wed May 24, 2006  at  07:41 PM

This is something that folks might want to look into itself -- although it's still controversial to some extent.

"Sudden acceleration" is not a hoax per se. Its spread was unintentional, and was initially believed by many, including some in the industry.
This all came to a head one evening in downtown Minneapolis, when a police van ran up onto the sidewalk during the annual "Holidazzle" parade. The van jumped the sidewalk, injuring a couple of folks and killing a child. The van continued to accelerate as it crashed into the window of a nearby store.

The police at first concluded it was a case of sudden acceleration -- I believe, in no way deceptively. They really believed it, as so many do.

The subsequent police investigation, including plenty of open debate on the subject in the media, concluded what many people already suspected: The driver of the police van hit the gas instead of the brake, and instinctively jammed on the "brake" harder when he started to accelerate.

This appears to be the cause of most, if not all, "sudden acceleration" incidents.

BMW is probably right about the user error. (Although, some models do appear more susceptible, because of the placement and size of the gas and brake pedals.)

If anyone owns a late-model BMW that they're worried might hurtle them helplessly into a tragic car wreck, I will nobly sacrifice myself by taking it off their hands for them.
Posted by SicTim  on  Thu May 25, 2006  at  06:32 AM
BNHS, I don't really see how a short in the cruise control would keep you from using the brakes, or changing gears to slow down, or setting the parking brake. In all the cars I've known of, cruise control only affects the accelerator, not the brakes, and the brakes can over-ride the cruise control if it starts doing weird things. I doubt that a car could pass inspections if every braking system depended on one little circuit.
Posted by Accipiter  on  Thu May 25, 2006  at  08:15 AM
There is no way possible that a short in the cruise control circuit could affect braking. The breaks are hydraulic, the pressure you put on the pedal depresses a hydraulic cylinder that in turn supplies pressure to all four brake calipers, or solenoids if it has drum brakes. Now I'm not sure how some of the very new "Drive by Wire" cars operate, but I would be willing to bet brakes are still just about the same. They may be enhanced (i.e. ABS, Traction Control, etc.) but even if taht all stops working your brakes will still stop you. Now if your car dies and you hit the brakes, it will be harder to stop as there is no power assist, but you can still stop.
Posted by Mikhail New  on  Thu May 25, 2006  at  02:18 PM
Originally posted by Marc:
"Hydroplane, not aquaplane. Aquaplaning is kneeboarding behind a motorboat."

An Aquaplane is a board for riding on water, pulled by a speedboat. However, when used as a verb it may describe either the action of riding on an aquaplane or to describe the slide of a vehicle uncontrollably on a wet surface.

The word hyrdroplane refers to a type of boat or submarine control surface, but can also be used (mainly in North America) as another term for the verb aquaplane.

Apologies for detracting from the main topic, but it really annoys me when people correct others wrongly.
Posted by Question Marc  on  Mon Aug 28, 2006  at  04:53 PM
The incident with the 36 year women in Texas is "exactly" what occurred with me while driving a VW Beetle. My car was totaled and I received a fracture that put me in a halo for 3 months. DON'T DRIVE ON WET ROADS WITH THE CRUISE CONTROL ON.
Posted by Sandra  on  Tue Oct 31, 2006  at  09:07 AM
I have owned a number of vehicles in my time with cruise control, and being an avid owners manual reader, I can tell you that they ALL warn against using CC in bad weather, ice, snow or rain. They also tell you not to use it in hilly/mountainous areas or in traffic (ie other cars & trucks.) So, for someone to say they NEVER heard of such a thing, it tells me that they never bothered to read the owners manual, a fairly common thing. I get this hoax in my inbox about twice a year. I guess no one ever thinks to check it out as a possible hoax. As for the 'sudden acceleration' theory, I have always said it was someone putting their foot on the accelerator instead of the break pedal. Maybe the pedals are too close together on some cars, maybe. When I first learned to drive, in high school in Drivers Ed, I drove stick shift cars, with a clutch. During that year we switched over to automatics. My instructor told us that since we might find ourselves driving either type of car, we should continue using BOTH feet, to stay in practice. This way, your LEFT foot is always used for the brake and your RIGHT foot is always used for the accelerator, and never the twain shall meet. I understand that nowadays they tell you to drive with ONLY the right foot. This is a recipe for disastor, to say the least. In a panic situation you may jam your right foot down, thinking you have hit the brake but find out, too late, that you hit the accelerator! So, we now have this new concept, 'sudden acceleration'. There is no such thing, unless there is a defect, either electrical or mechanical, in the vehicle. Take the transmission out of gear or turn the ignition off. Or, if it's the CC, turn IT off. There is no reason to crash.
Posted by PC Bob  on  Sun Nov 19, 2006  at  06:20 PM
The cruise control can definitely be a hazard. I had cruise on in cold, rainy conditions. No ice had been present for the last 40 miles. All of a sudden, I realize that the bridge that I just started crossing was iced over. The cruise control noted the decreased speed due to the bridge elevation and increased acceleration to keep going 65. At this time I have a white knuckle grip on the wheel and am trying to keep the car straight as hitting the brakes would make me slip off the road and I can't find the off button for the cruise control due to the white knuckled grip. Ends up the car gets across the icy bridge with a nice little squeak and wiggle at the end, with my wife waking up and looking at me and saying, why are you breathing so hard? I don't drive with it in slick conditions anymore.
Posted by M. Long  on  Tue Apr 01, 2008  at  10:30 AM
I believe the problem here does not lie with the cruise control but with the susceptibility of the driver to make a mistake which during rainy weather or icy conditions is more critical. When the cruise control is engaged, the driver's feet will be on the car's floorboard. In case a situation will arise wherein the driver will need to react quickly, there is a great probability of hitting the gas pedal instead of the brake as the driver's foot will come from rest. It will be different if one is driving with the cruise control turned off and the driver's foot will normally be on the gas pedal. When an emergency situation arises, the tendency will be to shift the foot on to the brakes.
Posted by Ahamay Maxim  on  Tue Oct 20, 2009  at  03:47 PM
Driving in the rain with the cruise control on is excedingly dangerous! My Grandad died because he had the cruis control on and was hydroplaning and didn't know it.
The moral of this lessons is:
Posted by Hoozey boy  on  Wed Feb 03, 2010  at  02:32 PM
I hit water on I-10 and hydroplaned out of control. Car was wrecked, I was OK. Cruise Control was on, and the split second delay in tapping the break vs. just letting Ur foot off the accelerator prob helped cause the accident. I am fortunate to not be injured, but the car is history. Whateever U think, plz NO Cruise Control in the Rain...
Posted by Mario  on  Fri May 14, 2010  at  04:59 PM
I have heard that cruise control is not ideal in icy or rainy conditions where you may need to take control suddenly. To be honest commen sense would say whenever you feel unsafe because of the weather, take cruise control off, slow down and pay attention to the road ahead.
Posted by sell bmw  on  Wed Jan 19, 2011  at  04:46 AM
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