Re: Cruise Control and Hydroplaning
From: Ray V.

The story about not using cruise control on wet or icy roads claims that if you do, your car will accelerate. That advice goes too far. The owner’s manual for my Ford advises, "Do not use the speed control in heavy traffic or on roads that are winding, slippery or unpaved." Notice it doesn’t mention "wet."

I have experienced the use of cruise control on both wet and slippery roads and can relate different experiences than the one reported by the Lincoln Town Car owner. I have done this in several different makes of cars. Here is what I have personally experienced:

On wet roads the cruise control works the same as dry conditions. I have hit puddles which did cause hydroplaning. When that happens the engine speed increases momentarily, then the cruise control disengages. Why? Because most cruise controls operate by monitoring a sensor on the drive shaft. If the drive shaft slows down, due to climbing a grade for instance, the cruise control tells the engine to speed up. On the other hand, when the car’s tires begin to slip (spin) in puddles or on slick pavement the cruise control tells the engine to do the opposite — slow down! This is because the drive shaft is speeding up.

But Detroit goes one step better. When the engine revs up quickly for that very brief moment of slippage, the cruise control senses this and disengages. From my experience the cruise control reacts as quickly as any driver would under such conditions.

Personally, I am very suspect of someone who says his Lincoln Town Car crashed because hydroplaning caused the cruise control to accelerate uncontrollably. Such a thing might occur due to a faulty cruise control unit regardless of highway conditions, but the scenario presented in the cybermessage needs closer examination.

In summary, I use my cruise control on "wet" highways. I do not use it when the road is "slippery."