Some drivers shy away from using cruise control because they think it will make their car go faster under certain conditions, like steep declines, and they won’t be able to respond in time to adjust. But unless you are using cruise control in wet or snowy conditions, cruise control will do what it is intended to do: Accurately maintain a desired speed without intervention from the driver, uphill or down.
Cruise control systems moderate the speed of your car the same way you do, by adjusting the throttle position. But cruise control engages the throttle valve by a cable connected to an actuator, instead of by pressing a pedal. The throttle valve controls the power and speed of the engine by limiting how much air the engine takes in. Many cars use actuators powered by engine vacuum to open and close the throttle. These systems use a small, electronically controlled valve to regulate the vacuum in a diaphragm. This works in a similar way to the brake booster, which provides power to your brake system.
How to Use
Cruise control systems vary by automobile, but all feature some form of switches that include ON, OFF, SET/ACCEL, RESUME, and, sometimes, COAST. These switches are usually located somewhere off the steering wheel, on their own stalk, separate from the windshield wipers or signal stalks. To set your speed, accelerate to your desired miles per hour and then tap the SET/ACCEL button. Take your foot off the gas, and now you are “cruising.”
If you wish to go faster, tap the SET/ACCEL button one time for each mile per hour you wish to increase your speed. On some vehicles, there isn’t a SET/ACCEL button. Instead, you move the entire stalk, either UP or FORWARD to increase speed, or DOWN and BACKWARD to decelerate, much as you would move your signal stalk. (If your system has a COAST button, hit this and you’ll slowly decelerate by one mile per hour until you hit SET/ACCEL again.)
How to Deactivate
Some cruise controls don’t have an OFF button. Instead, you exit cruise control and regain control of the gas pedal simply by pushing on the brake. In some cars, this simply pauses cruise control. You can reenter at whatever speed you accelerate to by pressing the SET/ACCEL button again—no need to press ON. At speeds below 30 mph, the control unit will prevent application of cruise control functions entirely.
Adaptive Cruise Control
Adaptive cruise control is similar to conventional cruise control in that it maintains the vehicle’s pre-set speed. However, unlike conventional cruise control, this system automatically adjusts speed in order to maintain a proper distance between two vehicles in the same lane. This is achieved through a radar headway sensor, digital signal processor, and longitudinal controller, usually located behind the front grill of the automobile. If the lead vehicle slows down, or if another object is detected, the system sends a signal to the engine or braking system to decelerate. Then, when the road is clear, the system will re-accelerate the vehicle back to the set speed. These systems usually have a forward-looking range of up to 500 feet, and operate at vehicle speeds ranging from around 20 miles per hour up to about 100 mph.
Unsafe at Any Speed
For long distance trips on relatively uncrowded interstates, cruise control is a must. It allows drivers to stretch their legs, and prevents the muscle cramping that can arise from holding the gas pedal for long periods of time.
But it is not an excuse to relax and stop paying attention to the road. Neither should cruise control should be used on wet, icy, or snowy roads or on roads with sharp bends.
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