Adaptive Cruise Control

Adaptive cruise control works like regular cruise control but will also slow down and speed up your vehicle with traffic. It doesn't rely on the driver to control braking and acceleration, making the technology much more useful on congested roads. And while this ability to speed up and slow down automatically might seem like magic, it's actually based on a technology that was first demonstrated more than a century ago.

The history of adaptive cruise control

Adaptive cruise control initially made its debut on the Mercedes-Benz S-Class and CL-Class luxury cars in 1999 under the name Distronic. Prior to that, companies like Mitsubishi and Toyota debuted features that functioned similarly to the Distronic system, but in the case of Mitsubishi, its lidar-based system could only warn the driver and Toyota’s system couldn’t apply the brakes.

The Mercedes version of the system used radar — first demonstrated successfully in 1904 — to determine its distance from the car in front, and it can use both throttle and brakes to attempt to maintain a set distance from that vehicle. Most of the adaptive cruise control systems in use today function similarly, though some systems use cameras or lidar to determine that distance. Some even use predictive models that account for the behaviors of drivers around them.

Many systems now offer stop-and-go functionality that will bring the vehicle to a complete stop with traffic and start off again when traffic begins to move — sometimes on its own and sometimes requiring a pedal or button input from the driver. Another hallmark of adaptive cruise control systems in today’s vehicles is the ability to set a distance range of usually three to five car lengths from the vehicle in front.

Problems with adaptive cruise control

Because adaptive cruise control is a complex system that interfaces with a number of key vehicle functions, problems with its functionality can occur. Often these problems will just restrict the use of adaptive cruise control until the issue has been resolved. Common issues can include:

• Obstructed cameras and sensors
• Poor weather conditions
• Oddly shaped lead vehicles
• Vehicles with reduced radar cross-sections

In these cases, adaptive cruise control functionality will return when the weather changes or sensors are cleaned. Occasionally, a dealer will need to recalibrate the adaptive cruise control system. This is especially true if the sensors are damaged.

Another problem can occur when a vehicle suddenly changes into your lane without a sufficient safe distance. The adaptive cruise control system may not recognize the vehicle time and therefore not slow sufficiently enough to prevent a crash. It's always advisable for drivers to pay strict attention to the road while adaptive cruise control is engaged.

Adaptive cruise control symbols

Using your car’s adaptive cruise system is often a fairly simple affair, but it will require you to understand some symbols and displays. For example, when activating cruise control, there is sometimes a different indicator on the dash to let you know whether you’re in regular cruise or adaptive cruise. This is a pretty critical one since you wouldn’t want to assume your vehicle will slow for traffic and have it not happen because you’re not in the right mode.

Another symbol to understand is the following distance indicator. This is usually shown as a series of lines in the dash display, sometimes with a little car representing your vehicle and another for traffic. Fewer lines mean you’ll be following more closely, while more lines mean the opposite. Maintaining an appropriate following distance based on speed is important because it can prevent your vehicle from making sudden dramatic changes in speed should traffic ahead slow quickly.

Next, you’ll need to be aware of the target speed that you’ve set your adaptive cruise control to try to maintain. Studies have shown that drivers using adaptive cruise control have more of a tendency to violate the speed limit. This is likely down to them setting a speed for one area and not changing that target speed if the speed limit drops.

Lastly, if you’re using adaptive cruise control and you touch the brakes (or the clutch, in the rare case of a manual transmission vehicle with this feature), it will cause the system to turn off and return control of the throttle to the driver. The system will typically still be on but not engaged. This status will most often be displayed as the set speed indicator going gray. If you press the resume button on your steering wheel or control stalk, it will reengage cruise control. That will often result in the set speed indicator turning green again.

Other names for adaptive cruise control

Adaptive cruise control is the widely acknowledged generic name for this technology, but many vehicle manufacturers have other names for the system in general. They include:

• Active cruise control
• Automatic cruise control
• Dynamic cruise control
• Intelligent cruise control
• Radar cruise control

Adaptive cruise is also included as a part of many advanced driver assistance system suites such as Tesla’s Autopilot, Hyundai’s Highway Driving Assist, Nissan’s ProPilot Assist and many more. In these systems, adaptive cruise is paired with features like automatic emergency braking, lane keeping assistance, automatic high-beam headlights and blind-spot warning. The goal of this integration is primarily to increase driver safety, with an added bonus of boosting driver convenience.