The CT6 is comfortable, fast, and well-featured. It even has seat massage. You'll like it. The 2018 CT6 with Super Cruise is on sale at Cadillac dealers now.

PORTLAND TRIBUNE: JEFF ZURSCHMEIDE - The full-size 2018 Cadillac CT6 offers Super Cruise semi-autonomous driving capabilities in the Premium Luxury and Platinum trim levels, and up to 400 horsepower from a three-liter twin-turbo V6 engine.Cadillac introduced the full-size CT6 sedan for the 2016 model year, but for 2018 Cadillac has chosen the CT6 as the flagship for its first semi-autonomous Super Cruise driving system. On a recent 800-mile road trip across the American southwest in the new CT6, my co-driver and I actually drove perhaps 50 miles. The Cadillac drove itself the rest of the way. Of course there are a bunch of asterisks and caveats on that, but it's still an amazing feat of technology.

Here's how it works: Cadillac sent out a fleet of drivers and mapped all 160,000 miles of the U.S. and Canadian Interstate highway systems very precisely using high-resolution GPS, laser radar (LIDAR), and cameras. The CT6 combines that map with its own systems to know the car's position within a few inches at all times. Cadillac's adaptive cruise control maintains a safe following distance from other cars.

To use the Super Cruise system, just drive onto the freeway normally. When the system is ready, it will display an icon on the dashboard. Push a button on the steering wheel and the top of the wheel glows green. That's your signal to take your hands off the wheel and let the CT6 drive itself. It feels strange to let go at first, but we got used to it after just a few minutes. You can take control back at any time by taking hold of the wheel or using the pedals.

PORTLAND TRIBUNE: JEFF ZURSCHMEIDE - The driver information display and the top of the steering wheel glow green when the Super Cruise system is activated. You can remove your hands from the wheel and let the Cadillac drive itself.Right now, the Super Cruise system works only on Interstate freeways. It won't take an exit, or change lanes to pass a truck. It just drives right down the center of the lane you selected. Super Cruise keeps to your set speed or lower, depending on traffic. But it will follow the road around curves and over long distances, qualifying the CT6 as the first Level 3 autonomous vehicle offered for sale in America.

The Super Cruise system also requires the driver to keep watch on the road ahead. There's a camera on the steering column that makes sure you're paying attention. If you look away to adjust the audio system or fiddle with something else for more than a couple seconds, the system beeps to remind you to look ahead. Sorry, but you can't take a nap or watch a movie just yet.

You can split hairs over the question of whether this is truly an autonomous car, but it's certainly well beyond anything else currently offered for sale, and the Super Cruise system does everything Cadillac says it will do.

Before we're done, I should talk about the rest of the car. It's a top-of-the-line Cadillac, so it's really nice. The CT6 is comfortable, fast, and well-featured. It even has seat massage. You'll like it. The 2018 CT6 with Super Cruise is on sale at Cadillac dealers now.

2018 Cadillac CT6 Platinum AWD

Base price: $88,295

Price as tested: $89,890

Type: Full-size sedan

Engine: 3.0-liter twin turbo V6 (404 hp, 400 lbs-ft)

Transmission: 8-speed automatic

EPA estimated mileage: 18/26

Overall length: 204.1 inches

Curb weight: 4,399 pounds

Final assembly: Detroit, Michigan