Car Talk: ‘On-off’ safety feature means you can cruise and relax

Dear Car Talk:

My husband tends to leave the cruise control on after driving my car (and who knows how often he does this with his own car?).

What are the negative effects of this practice? I assume there are some, or manufacturers wouldn’t give us the option of turning the cruise control switch on and off. Am I right in this assumption? — Carrie

I’d be much more worried about him leaving the oven on, Carrie.

He’s actually not doing any harm to the car by shutting off the engine with the cruise control main switch still on. Here’s why:

The primary purpose of the cruise control’s main “on-off” switch is not to get you to turn it off. It’s to force you to turn it on.

It’s a safety step. Most cars have switches to set or resume the cruise control on the steering wheel or one of the column stalks. They’re located there for your convenience, making them easy to reach. But, as you can imagine, making them that convenient can also make it easy to hit one of those buttons by accident.

To make the system a little safer, the car, by default, always starts with the main cruise control switch turned off. That way, if your finger accidentally hits the “resume” button instead of the “volume up” button, nothing bad will happen. The car won’t suddenly speed up and cause you to panic.

To get the cruise control to work, each time you drive the car, you have to affirmatively turn on the main cruise control switch first. Then those steering wheel controls will work.

So, when your husband shuts off the engine — even if the cruise control main switch is still on — rest assured the cruise control will turn itself off.

You can test this for yourself, Carrie. Next time your husband commits his cruise control crime, have a look the next time you drive the car. The cruise control will be off. And you can reassure your husband that they had him in mind when they made the system idiot proof, Carrie.

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