Safe Speed Forums

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 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 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 lose contact with the pavement, your car will accelerate to a higher rate of speed [sic] and 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 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.

I heard a version of this story which identified the make and type of car, and it turned out that it was indeed fitted with traction control triggered off non-driven wheels. It's a silly thing to do, but I think the story's true.

This would depend on whether the driven wheels were the ones monitored for rotational speed, I would imagine this would be the case but I can’t say for certain.

- If the rear wheels are driven and monitored: the system will keep the rear wheels at a constant rotational speed; I can’t see how this could be a significant problem.
- If instead the rear wheels are driven and the front wheels monitored: the system could apply more power to the rear wheels potentionally causing a spinout.

I find it difficult to believe that car designers could be that daft!

In short: drive power must be reduced if the rotational velocity of the driven wheels is greater than the rotational velocity of the non-driven wheels.

Which rear wheel would you like to monitor?

Unless the vehicle is travelling in an absolute straight line and with identical wear on identical tyres, then the wheels are all rotating at different speeds.

I did say ‘wheels’


Long term offset drift can easily be factored in (I don’t know if it actually is).
Chances are you won’t be steering enough for the effect to be significant if you’re using cruise control.

Like I already said, I find it difficult to believe that car designers could be so daft as to design cruise control systems which could be fooled to behave so erratically; I only stated how it could be possible.

Long term offset drift can easily be factored in (I don’t know if it actually is).
Chances are you won’t be steering enough for the effect to be significant if you’re using cruise control.

I was really surprised at how bad their tyres are the first time I drove in the rain in California.

- concrete road surface offers much less grip than tarmac when wet.

Not always the case. Interstate roads in the US have grooved congrete roads made on a continuous casting process. The grooves give excellent drainage.

Two other problems are:

- concrete road surface offers much less grip than tarmac when wet.
- 11+ months of hot dry weather allows an accumulation of oil and rubber that's very slippery when it (finally) gets wet.

This would depend on whether the driven wheels were the ones monitored for rotational speed, I would imagine this would be the case but I can’t say for certain.

- If the rear wheels are driven and monitored: the system will keep the rear wheels at a constant rotational speed; I can’t see how this could be a significant problem.
- If instead the rear wheels are driven and the front wheels monitored: the system could apply more power to the rear wheels potentionally causing a spinout.

I find it difficult to believe that car designers could be that daft!

cant imagine the grooves do much for the contact area tho'