How does Adaptive Cruise Control work?

Adaptive or Active Cruise Control (ACC) has been available on cars for a long time but is only now being implemented on motorcycles.

Ducati was the first company to announce that a Bosch ACC system would be fitted to some of their high-end models, this was quickly followed by similar announcements by both KTM and BMW.

Bosch ACC system
Bosch ACC system

How does ACC work?

Regular cruise control systems allow you to set your vehicle’s speedometer to a specific speed that remains constant until you deactivate the cruise control mechanism. Adaptive cruise control works similarly to standard cruise control systems; however, your speed and distance are automatically adjusted based on a vehicle directly in front of you using millimeter-wave radar that has around a 100M range.

The radar sensor detects the vehicle in front and keeps a constant distance from it, by continually adjusting the speed and brakes to maintain the distance. Riders that have used the system say that the acceleration and braking are very smooth and does not feel strange or unnerving when riding. According to BMW, their ACC algorithm ramps up braking over a period of 1.5 seconds and limits deceleration to about 0.5g. This is about half of R 1250 RT’s maximum braking force.

The system also adjusts depending on the lean angle of the bike. The radar is not so good at seeing around corners, so adjusts accordingly. That said, the Ducati system has the ability to continue functioning, up to a lean angle of 50 degrees. Imagine that, you can be down on your knee slider and still maintain a safe distance to the rider or vehicle in front. Very Italian!

All this tech and algorithm stuff sounds simple, right? In theory, yes, but when you throw in the dynamics like learn angle and the relatively slim and small footprint of a motorcycle, things become a little more complicated. The trick is to make complicated simple and intuitive for the rider. Based on what I have seen to date, most ACC systems have achieved that.

Bosch ACC system
Bosch ACC system
Bosch ACC system
Bosch ACC system

How does the rider set this up?

Systems are usually able to be activated once the motorcycle is traveling over 20 MPH. Plus requires the bike’s traction control and ABS to be active. The rider can set the cruise speed and has the option to set the distance to the vehicle in front.

The system can be overridden by either accelerating, braking, or pulling in the clutch for more than 1.5 seconds. Changing gears does not affect the ACC settings.

The rider receives feedback and warnings on the dash. E.g., If the vehicle in front suddenly brakes. Likewise, stationary vehicles are not included or detected by the system, it’s still down to the rider to avoid these.

Bosch ACC system Controls
Bosch ACC system Controls
Bosch ACC system Controls
Bosch ACC system Controls

The ACC system does not apply the brakes in an emergency for obvious reasons, it could be very dangerous to the rider. Although I have no doubt Emergency Braking Systems will arrive at some stage in the future as greater rider acceptance of ACC systems and technology improves.

What about overtaking?

The ACC system stays active providing the indicators are used to make the overtake. The system detects the overtake, deselects the vehicle in front, and reselects the new vehicle in front when you move back into the lane.

Blind Spot Detection (BSD)

Some systems also have a rear radar. This radar allows for blind-spot detection, warning the rider via the dash or mirror indicators that a car is in its blind spot. This helps avoid the dangerous scenario of pulling out into the path of an oncoming vehicle.

Are Active Cruise Control (ACC) systems safe?

According to Bosch, the first and to date main supplier of ACC systems. One in seven motorcycle accidents could be prevented using radar-based assistance systems.

Using ACC the rider can focus and concentrate more on the traffic situation.

The ACC systems assist or help the rider in critical situations. E.g. A car in the blind spot or aggressively braking in front of you.

ACC systems are riding aids that can often respond much quicker than the rider, helping avoid accidents or potential issues.

ACC systems make for more comfortable and relaxed riding, especially on highways or long days in the saddle on boring open roads.

Real-World Feedback

As of this article, most rider and journalist reviews have been very positive of ACC systems. Looks like many of the skeptics have been converted!


Overview of the ACC system used by KTM.