What Is the Purpose of Cruise Control in a Car?

Cruise control’s purpose is to automatically maintain a driver-selected speed without continuous accelerator input, reducing fatigue on long drives and promoting consistent, legal, and often more efficient driving. In newer vehicles, adaptive cruise control extends this by also regulating following distance from the car ahead, but the driver must remain attentive and ready to intervene.

How Cruise Control Works

Conventional cruise control is a speed-holding aid. After the driver accelerates to a desired speed and activates the system via a steering-wheel button or stalk, the vehicle’s engine or motor controller adjusts throttle electronically to keep that speed steady. Pressing the brake (and the clutch in manual-transmission cars) disengages the system; resume and set/coast functions allow fine adjustments. While early systems used vacuum actuators, modern cars rely on precise drive-by-wire electronics integrated with the powertrain control unit.

Adaptive Cruise Control (ACC)

Adaptive cruise control builds on basic cruise by using radar, cameras, or lidar to maintain a set time gap to the vehicle ahead, automatically slowing or accelerating as traffic ebbs and flows. Many current systems can handle stop-and-go conditions, resume after brief stops, and adjust speed based on detected speed limits or navigation data on curves or exits. Despite these advances, ACC is a driver-assistance feature, not self-driving: the driver must supervise, keep hands on the wheel, and be prepared to brake at any time.

Key Benefits

The following points outline the principal advantages drivers experience when using cruise control on appropriate roads and in suitable conditions.

• Reduces driver workload and fatigue on long, steady highway trips.
• Promotes speed consistency, which can improve fuel economy or range in many scenarios.
• Helps avoid unintentional speeding by locking in a legal speed.
• With ACC, smooths traffic flow by moderating accelerations and braking.
• Enhances comfort by minimizing constant pedal modulation.

Collectively, these benefits can make highway travel less tiring and more efficient, particularly when road and weather conditions are stable and predictable.

Limitations and Safety Considerations

While useful, cruise control has clear limits and should be used with judgment to preserve safety and control.

• Not suitable on wet, icy, or loose surfaces where traction can suddenly vary.
• Less effective on steep or winding roads, where speed maintenance may conflict with safe cornering or grade changes.
• Requires constant driver attention; it is not autonomous driving.
• Sensors in ACC can be impaired by heavy rain, snow, fog, dirt, or direct sunlight glare.
• Overreliance can dull situational awareness; scanning the road remains essential.

Understanding these constraints helps drivers deploy cruise control where it thrives—open, dry highways—while disengaging it when conditions demand direct control.

Best Practices for Use

To get the most out of cruise control while maintaining safety, consider these practical guidelines.

1. Engage it primarily on open, dry highways with light, predictable traffic.
2. In ACC, set a generous time gap; longer following distances improve comfort and safety.
3. Keep hands on the wheel and feet ready to brake; remain vigilant for cut-ins or hazards.
4. Turn it off in heavy traffic, construction zones, poor weather, or on curvy, hilly routes.
5. Adjust the set speed to match changing speed limits and road conditions.

Used this way, cruise control remains a helpful assistant rather than a substitute for attentive driving.

When Cruise Control Helps Fuel Economy—and When It Doesn’t

Maintaining a steady speed often reduces unnecessary acceleration, aiding fuel economy or EV range on flat highways. However, on hilly terrain, a fixed-speed strategy can trigger downshifts and hard throttle to hold speed uphill, which may be less efficient than allowing modest speed variation. Some vehicles offer “eco” or “adaptive” logic that relaxes speed-holding on grades for better efficiency. In EVs and hybrids, fine control of regenerative braking and coasting also affects results; smooth, anticipatory driving can match or beat cruise control in rolling terrain.

The Bottom Line

Cruise control is designed to hold a chosen speed, easing driver workload and supporting consistent, often more efficient and lawful driving. Adaptive systems add distance-keeping for comfort in traffic but still require full driver supervision. Used judiciously and in the right conditions, it’s a valuable tool—just not a replacement for attentive, skilled driving.

What are the benefits of cruise control in a car?

Cruise control eliminates the need to maintain constant pressure on the accelerator pedal, reducing driver fatigue during long trips. This allows for a more relaxed driving experience, particularly on highways and open roads.

When should I use cruise control?

Use cruise control for long drives on straight, flat, and open roads with good weather and light traffic to reduce driver fatigue and improve fuel efficiency. Avoid using it in congested urban areas, on slick, wet, or icy roads, on winding roads, in heavy traffic, or on steep hills, as it compromises safety and control in these conditions. Always remain attentive and ready to take manual control when using cruise control.
 
When to Use Cruise Control

• Open, Straight Highways: Ideal for long stretches of road where the speed limit is consistent. 
• Light Traffic: Best when there are few other cars on the road, allowing for consistent speed without frequent adjustments. 
• Good Weather Conditions: Use it when roads are dry and clean. 
• Level Terrain: Works best on flat roads, though modern systems can handle some gentle slopes. 
• Long Trips: It helps reduce driver fatigue by keeping the throttle steady, allowing you to relax your leg. 
• Fuel Efficiency: Maintaining a consistent speed can improve gas mileage compared to constant acceleration and deceleration. 

When to Avoid Cruise Control

• Heavy Traffic and City Driving: Opens in new tabThe frequent stops and starts of city driving are not suited for cruise control. 
• Slick, Wet, or Icy Roads: Opens in new tabThese conditions require precise control, and cruise control could react poorly to a skid or loss of traction. 
• Curved Roads and Hills: Opens in new tabMaintaining a consistent speed isn’t appropriate for navigating turns or significant changes in elevation. 
• Adverse Weather: Opens in new tabAvoid use in rainy, foggy, or icy conditions. 

Tips for Safe Use

• Stay Attentive: Cruise control is a convenience, not a replacement for an attentive driver. 
• Be Prepared to Take Over: Keep your foot near the brake or accelerator and be ready to disengage the system at any moment. 
• Monitor Traffic and Road Conditions: Constantly check your surroundings and be aware of any potential hazards or changes in road conditions. 

What are the disadvantages of cruise control in a car?

Cons of Using Cruise Control

• Reduced situational awareness.
• Decrease in EEMG brain wave activity.
• Increased driver fatigue.
• Reduction in eye movement.
• Increase in distracted driving.
• Reduced reaction time.
• Increased stopping distances.
• Reduced directional control.

Can you brake on cruise control?

Yes, you can brake on cruise control; braking by pressing the brake pedal will deactivate the system, requiring you to manually resume it later. However, adaptive cruise control (ACC) systems can also use their own brakes to maintain a set following distance, which is different from you manually applying the brakes.
 
Standard Cruise Control

• Deactivates when you brake: Opens in new tabPressing the brake pedal is a programmed fail-safe that turns off the cruise control. 
• Requires manual resume: Opens in new tabAfter you’ve finished braking, you’ll need to press the “RESUME” button or re-engage the system to reach your previous speed. 
• No engine braking: Opens in new tabMost standard cruise control systems don’t use the brakes; instead, they might downshift or cut power to control speed, especially on descents. 

You can watch this video to learn how standard cruise control works and how to use the resume button: 1mMick Drives CarsYouTube · Nov 1, 2023
Adaptive Cruise Control (ACC)

• Uses its own brakes: Opens in new tabACC systems are designed to automatically slow down to maintain a set following distance from the car ahead. 
• Can stop the vehicle: Opens in new tabMany modern ACC systems can bring the vehicle to a complete stop in traffic and then resume following when the traffic moves again. 
• Limited braking: Opens in new tabWhile ACC can brake, it has limited capacity, so it may provide a warning to apply the brakes yourself if a sudden stop is needed. 
• You still need to brake: Opens in new tabACC systems do not detect stop signs or red lights, so you must use the brake pedal manually for those situations. 

This video demonstrates how adaptive cruise control works, including stopping and resuming: 1mGM BullfrogYouTube · Mar 17, 2021
In summary: Braking with your foot will always turn off standard cruise control. For adaptive cruise control, you can still brake, but you should be aware that the system also has its own braking capabilities to manage speed and distance from other vehicles.