Adaptive Cruise Control

Story by David Booth//
August 17 2021

Judging by the discussions I’ve seen on the blogosphere, we motorcyclists remain quite technologically conservative. Neanderthals, really. According to my ad hoc survey — which comprised reading comment sections — about half of us are dead set against the new adaptive cruise control (ACC) systems recently launched by BMW and Ducati (soon to be joined by Kawasaki, KTM and Indian).

This antipathy to things electronic isn’t anything new to us bikers. Anti-lock brakes were initially greeted as unnecessary and even dangerous, with Harley riders seemingly rejoicing in their preference to “lay ‘er down” rather than use the front brake. Ditto our skepticism of traction control, which seems positively silly today, what with 200-horsepower supercharged streetbikes.

We should have no reason to fear by adding radar-controlled cruise control to that list of technologies. In principle, it’s quite simple. Take an ordinary, everyday cruise control system and add a radar sensor mounted in the front fairing. Said sensor will detect a vehicle ahead and, using signals from the ABS, use either the brakes or the throttle to maintain a set distance from that vehicle. Yes, you can vary said distance, but that’s essentially the crux of ACC systems; instead of having to disable “cruise” when you catch up to some slow poke — and then hit “resume” after you pass them — the onboard computer handles it all for you. But the devil, as always, is in the details, and even though BMW and Ducati both use Bosch sensors and software, they operate a little differently.

For instance: while BMW offers three set distances — actually measured in time — from the vehicle ahead, Ducati offers four. In practice, they’re not so much different, though, as you’d suspect from an Italian company, the Multistrada V4S I rode was, shall we say, more comfortable being close to the rear bumper ahead.

The other marked difference was in how aggressively the ECU would apply the throttle when you hit the “Res” button or pulled out to pass a car. Again, the two bikes differ, with BMW offering two choices of performance — Comfort and Dynamic — while Ducati offers just one. That said, BMW’s Comfort mode is all but useless, causing the bike to accelerate so slowly that little old ladies from Pasadena might flash you the finger. Dynamic feels more natural and (electronically) twists the throttle sufficiently so that, when you pull out to pass, the rate of acceleration feels at least adequate. Unsurprisingly, the Ducati is again more forceful with its throttle application, and the big Multistrada’s “resume” function is more aggressive than anything else I’ve driven, two-wheeled or four.

One of the difficulties for all ACC systems — again, both two-wheeled and four — is knowing when to start accelerating when pulling out to pass. Accelerate too soon, and one risks passing too closely to the vehicle ahead; too late, and you’re basically a rolling roadblock — an inconvenience at the best of times. The Ducati version was, again, more eager to get ahead of traffic, accelerating sooner and harder to merge into the passing lane.

But all of the above considerations apply to cars as well as bikes. What makes two-wheeled applications more difficult is that motorcycles lean and cars don’t, which means the radar sensor’s field of vision changes dramatically. Indeed, as far as the ACC’s computer knows, the car ahead may have suddenly disappeared. Bosch handles that conundrum with delicacy in both throttle and brake application, to account for lean angle. Whatever the software specifics, in my experience — about 5,000 km in mixed conditions — both handled following cars and trucks through corners quite safely.

One aspect of motorcycle riding that may still confound these radar systems is riding with a group of motorcyclists. More specifically, what if you ride in a tightly-packed “staggered” formation, which puts you closer to the motorcycle ahead? Indian is working on a system that addresses this, allowing the rider to choose from different allowable following distances, according to type of vehicle. Presumably, that would allow bikers to ride in tight formation. In the meantime, I can attest that both radar systems work when you’re following directly behind another motorcyclist, but can be blind to the biker ahead if they are riding on the opposite side of the lane.

The same common sense would seem to apply to low-speed operation. Some more advanced automotive systems — usually called “Stop and Go” — can resume speed even after coming to a complete stop. Bosch’s motorcycle systems, on the other hand, are designed to disengage long before you come to a stop, if for no other reason than preventing the rider from becoming so distracted that they forget to put their feet down.

In the end, both systems worked pretty flawlessly. My passenger preferred the more sedate BMW system; when I was riding alone, the more aggressive Ducati system was my favoured “tuning.” Indeed, even at speeds up to 160 km/h — I tested the Multistrada in its native Italy — I’d run the V4S on ACC until it was out of gas. That said, the faster I went, the longer the following distance I programmed into the radar system. At a buck-sixty, one’s faith in technology has its limits.

Editor’s note: Though these Adaptive Cruise Control systems can slow the motorcycle down, they are not emergency braking devices. The BMW, for instance, is limited to about 0.5 g of deceleration, about half the maximum the R1250RT is capable of generating. If the rider does not then apply the brakes themselves, then the motorcycle might, high-tech radar sensors or no, hit the vehicle ahead. Bosch may actually upgrade the system for Automatic Emergency Braking, but right now, that’s not how the system works.

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