# Cruise control questions **URL:** \ **Category:** Factual Questions\ **Created:** [November 25, 2005, 7:41am UTC](https://boards.straightdope.com/t/cruise-control-questions/332664 "2005-11-25T07:41:53Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [November 25, 2005, 7:41am UTC](https://boards.straightdope.com/t/cruise-control-questions/332664/1 "2005-11-25T07:41:53Z")
Why do crusie control systems have on and off switches? Is there some disadvantage to having the CC system on all the time? Why is there a lag between when you hit the set speed button and when the speed is read by the CC? With computer controlled CC, you’d think it could read the speed immeditately. Is this just a holdover ‘feature’ from the pre-digital CCs of yesteryear or is there still a reason for this? ---
**Author:** ![pool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pool/32/4152_2.png) [@pool](https://boards.straightdope.com/u/pool)\ **Post date:** [November 25, 2005, 7:45am UTC](https://boards.straightdope.com/t/cruise-control-questions/332664/2 "2005-11-25T07:45:08Z")
Well, I’m guessing the on/off switch is a safety precaution so the CC is not accidentally triggered somehow and causes a wreck, though I admit it seems unlikely to happen. ---
**Author:** ![Waterman](https://avatars.discourse-cdn.com/v4/letter/w/b2d939/32.png) [@Waterman](https://boards.straightdope.com/u/Waterman)\ **Post date:** [November 25, 2005, 7:56am UTC](https://boards.straightdope.com/t/cruise-control-questions/332664/3 "2005-11-25T07:56:27Z")
My car has a dashboard switch for either activating or deactivating (my choice of words) the cruise control. This switch does not however, actually put the car into cruise control mode. To put the car under cruise control I must push the steering wheel mounted “Set/Cruise” switch to activate the cruise control. Once this button is switched it puts the car into speed control based on the speed at the time that I pushed the button. I can, once in actual cruise control, decrease the speed by pressing the “Set/Cruise” button or increase speed by pushing the resume “Resume/Accelerate” button. I can press the “Off” button on the steering wheel or press the brake or clutch in and it will turn the cruise off and return speed control to my control of the gas pedal. FWIW, I leave the dashboard button in the on position all the time with no ill effects but again I must actually push the “Set/Cruise” button to activate the cruise control. ---
**Author:** ![KlondikeGeoff](https://avatars.discourse-cdn.com/v4/letter/k/3e96dc/32.png) [@KlondikeGeoff](https://boards.straightdope.com/u/KlondikeGeoff)\ **Post date:** [November 25, 2005, 4:51pm UTC](https://boards.straightdope.com/t/cruise-control-questions/332664/4 "2005-11-25T16:51:45Z")
I’ve had cars where you have to turn on the CC switch every time after turning off the ignition and starting again. Other cars will leave the switch on all the time, have no idea why. Assume it is a saftey feature, yet as you have to Set the CC to activate it, can’t see how this is much of a safety thing. Maybe an automotive engineer will come along to answer it. Slight hijack, but may be of interest to you if it can be answered: When going downhill, the CC will activate the brakes to keep a steady speed. I always wonder if that puts on the brake lights too. Anybody know? ---
**Author:** ![Waterman](https://avatars.discourse-cdn.com/v4/letter/w/b2d939/32.png) [@Waterman](https://boards.straightdope.com/u/Waterman)\ **Post date:** [November 25, 2005, 5:45pm UTC](https://boards.straightdope.com/t/cruise-control-questions/332664/5 "2005-11-25T17:45:51Z")
> [@KlondikeGeoff](#): > > Slight hijack, but may be of interest to you if it can be answered: > When going downhill, the CC will activate the brakes to keep a steady speed. I always wonder if that puts on the brake lights too. Anybody know? FWIW, I have never had or been in a vehicle that activated the brakes when using cruise control. Normally the cruise will adjust the amount of gas and this sometimes can feel like the brakes are being applied. ---
**Author:** ![KlondikeGeoff](https://avatars.discourse-cdn.com/v4/letter/k/3e96dc/32.png) [@KlondikeGeoff](https://boards.straightdope.com/u/KlondikeGeoff)\ **Post date:** [November 25, 2005, 5:57pm UTC](https://boards.straightdope.com/t/cruise-control-questions/332664/6 "2005-11-25T17:57:29Z")
> [@Waterman](#): > > FWIW, I have never had or been in a vehicle that activated the brakes when using cruise control. Normally the cruise will adjust the amount of gas and this sometimes can feel like the brakes are being applied. Yup, seems like most cars do just adjust the gas (you can feel the accelerator pedal go down when climbing), but my old Honda Accord definitely braked on steep downhills after it cut the gas.