Dear Tom and Ray:

My husband and I are the proud parents of a 16-year-old boy. Yes, he does have his driver's license. Oh my! While he was driving 70 mph on the interstate on a rainy night, he had a hard time hearing my suggestion that he slow down and cancel the cruise control. He thought that I (Mom) was interfering with his driving and that I didn't understand modern technology. He said that just because I drove for years without this device doesn't mean he needs to do the same. My son's opinion is that cruise control is meant for the interstate and higher-speed situations, and is not influenced by rainy weather, nighttime driving or crowded roads. He thinks that he can stop quickly, and he likes cruise control because he doesn't vary his speed so much. My son's thoughts concern me. Besides going too fast for unsafe conditions, I don't think cruise control helps my son learn to stay alert and develop a feel for the car he is driving. Fortunately, this situation was temporarily resolved by my son being replaced by his father, and we did get to our destination safely. Please help settle our disagreement. What is the "purpose" of cruise control? Thanks. -- Joyce

TOM: Isn't it interesting how human knowledge and wisdom seem to peak temporarily at age 16, Joyce?

RAY: This kid could use a gentle dope slap. The first issue to address is speed itself. If he's been driving for a few months, and he's going 70 mph at night in the rain, he might not understand the laws of physics -- which, I'm sure he'll be surprised to learn, do apply to him.

TOM: Second, you're absolutely right about cruise control. It's a convenience designed to be used on wide-open roads; it's dangerous to use it in moderate to heavy traffic. A good rule of thumb is that if you have to cancel the cruise control -- because you've come too close to another car -- more than once in a 10- or 15-minute period, you probably shouldn't be using it in those road conditions.

RAY: Cruise control can be beneficial on long highway drives. It can help keep you from speeding up accidentally, and it saves fuel by not varying your speed too much.

TOM: But when you're in traffic or when visibility is limited or road conditions are poor, cruise control can be dangerous. Normally, when an experienced driver sees a situation ahead that may require him to brake, he lifts his foot off the gas pedal and holds it over the brake while assessing the situation. If it proves to be nothing, his foot goes back on the gas. If a car is stopping up ahead or there's something in the road, he steps down on the brake.

RAY: During that crucial time when his foot is off the gas, the car is beginning to slow down, making his stopping distance shorter -- whereas if the cruise control is on, the car is maintaining its speed while the driver makes his assessment. And at highway speeds, those extra seconds before you release the accelerator can mean the difference between being able to stop or swerve in time and performing an unplanned government crash test.

TOM: The same is true if you hit a big puddle with the cruise control on and start to hydroplane. You don't want the car continuing to try to accelerate once you're already hydroplaning, even for a few seconds.

RAY: So, you're right, Joyce. The question is, How do you get a kid who thinks he already knows everything to stop using the cruise control in heavy traffic?

TOM: I know what I'd do if I were you. I'd take the car to my mechanic and have him disconnect the cruise control. It's easy to do, and easy to reattach if you want it back someday (after he goes to college).

RAY: Good idea. When Junior asks what happened, tell him he must have broken it by overusing it. And if he continues to drive too fast for the conditions, use the same solution you used last time: Have Dad drive, and put him in the back seat. It's harsh, but it's your job to keep him alive until he's wise enough to do it himself.