Driving in the rain - Do NOT use that Cruise Control!

Since 11-09-04

Check out what UrbanLegends says about this issue

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. We tell our teenagers to set the cruise control and drive 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 had a similar accident, totaled his car and sustained severe injuries. If you send this to people and only one of them doesn't know about this, then it was all worth it. You might have saved a life.

From: Jack Walker
Sent: Tuesday, November 09, 2004 12:35 PM
To: James Santos
Subject: RE: Emailing: driving_in_the_rain__no_on_cruise_control

 Jim,

      Let me clarify my previous email as I guess it is considered a somewhat "true" myth.  I share the doubts about the details of the problem with the snopes website however. 

       If you are traveling at a fixed rate of speed, the wheels are turning at the proper speed.  If you start hydroplaning, the cruise control would continue to turn the wheels at the same speed because that is what the cruise control is measuring.  So the question arises, why does the car go faster if the wheels are turning at the same speed?  If a hydroplaning situation, the wheels would be slipping through the water so the car motion would be slower than the apparent rotation of the wheels, not faster. 

       While I would agree that loss of control is a likely consequence of using the cruise control in rain, the apparent acceleration of the vehicle is a very dubious claim just by looking at the basic physics of the situation. 

       I would note that in times I've hydroplaned (without cruise control!) I did not note any sudden increase in speed.  In that case, I was maintaining a fixed accelerator position so hydroplaning caused a noticeable increase in the wheel rotation as the drop in friction caused the engine speed to increase.

 Jack