Business

Hiawatha Bray | Tech Lab

A not so self-driving Cadillac

A 2018 Cadillac CT6
Aram Boghosian for The Boston Globe
A 2018 Cadillac CT6

I’m not in the habit of driving a $90,000 car between Boston and Foxborough. I’m even less accustomed to having the $90,000 car do the driving. So the car and I took turns.

The car is a Cadillac CT6. It’s similar to one I tested back in August 2016, which was almost-but-not-quite-capable of driving itself down the interstate. The 2018 edition is a big step forward. It features Super Cruise, billed by General Motors Corp. as “the world’s first true hands-free driving system for the freeway.”

Note those last three words. Super Cruise doesn’t work on the streets leading to the freeway, or even the onramp. Let the rival Autopilot system from electric carmaker Tesla tackle the Byzantine complexity of city streets. Super Cruise keeps things simple. It works only on high-speed roads, free of nuisances like intersections and stoplights.

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It’s remarkable, but it’s not self-driving. It’s not even close. Forget about reading the paper or playing “Minecraft” as you race toward the Zakim Bridge. Driving the CT6 is a pleasure, but it’s nonstop work, even in Super Cruise.

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The system works only on 130,000 miles of US highways that have been measured with lasers by GM, to produce maps accurate to the square inch. That’s the kind of precision you want when there’s a gasoline tanker truck in the next lane. Thanks to GPS, the car knows when it’s on a compatible stretch of highway, such as I-95 South. Super Cruise won’t activate unless it’s on the right kind of road.

The CT6 is covered with radars and cameras that can spot the lane markings and detect cars ahead and to either side. It can speed up or slow down to maintain a safe interval, and steer to keep the car properly aligned as it takes a curve at 65 miles per hour with eighteen-wheelers on either side. But Super Cruise won’t automatically change lanes, take exit ramps, or make turns.

You launch the Caddy’s cruise control, then wait for the Super Cruise logo to appear on the CT6’s digital dashboard. When you see it, push a button. The top edge of the steering wheel emits a friendly green light, and that’s that. Even at night, on a pitch-black stretch of Interstate 95, the system had no trouble finding its way.

But I wouldn’t put your hands in your lap and enjoy the ride. Even when the self-driving system has everything under control, GM expects you to do everything you would normally do. A camera mounted on the steering column tracks your head and eyes. If you turn from the road for more than a few seconds, alarms clang and red lights flash.

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The overall effect is a little creepy. You sit watching the movements of other vehicles, constantly tempted to hit the gas or the brake or to switch lanes. But you must stop yourself, take a deep breath, and trust the software. It’s like letting your teenage child take a spin for the first time and expecting to grab the wheel when he does something crazy. Happily, Super Cruise navigated with a precision that at times approached the magical.

Still, it’s just as well that Super Cruise demands your attention; there are some road conditions it can’t handle. When an onramp dumped merging traffic into my path, I had to grab the wheel, hit the gas, and have the car’s twin-turbo 400-horsepower V-6 engine pull me out of harm’s way. GM also warns that the car cannot accurately navigate in construction zones.

And of course, you inevitably come to the end of the highway. When the Caddy’s GPS saw I was approaching my off-ramp, Super Cruise switched itself off and ordered me to take over.

Fancy tech like this has a way of migrating down to cheaper cars, but the process takes years. By then, we’ll probably see systems far more impressive than Super Cruise. Last week, GM said it plans to introduce a self-driving car sometime next year that’s based on its mid-priced Bolt EV electric vehicle and designed for Uber-like ride-hailing services. Called Cruise AV, it will lack many of the amenities found in the Caddy, including the illuminated steering wheel. In fact, the Cruise won’t have a steering wheel at all, or brakes or an accelerator. Passengers would just climb in and ride.

The sort of consumer who’d pay $90,000 for a CT6 would probably want to drive it, at least once in awhile. I’m the type who just wants to get there, and I’d be glad to just let GM take the wheel.

Hiawatha Bray can be reached at hiawatha.bray@globe.com. Follow him on Twitter @GlobeTechLab.