Semi-autonomous Mercedes automatically adjusts its steering
Mercedes' semi-autonomous 2018 S-Class features automatically adjusted steering and lane-change assist to ease manoeuvres, and can automatically slow down for turns in the road. The model's updated driving assist system also offers monitoring graphics that are easier to use than earlier systems. In situations where cameras and sensors can't prepare the car for a manoeuvre, the car uses map data to modulate its approach, said Mercedes engineer Bernhard Weidemann. Mercedes will offer the model in eco, comfort and sport modes.

Robocars are a bit like infants—we teach them in steps. First, humans gave them the ability to drive down the highway without smashing into things. Then humans taught them to change lanes without smashing into things. Now, self-driving vehicles finally mastering taking turns without smashing into things. The methodical German engineers behind the 2018 Mercedes-Benz S-Class want their baby to move beyond simplistic freeway driving, and onto the roads that wind through towns, villages, and cities. You know, the complicated ones.

The Mercedes flagship’s secret sauce is in its updated semi-autonomous adaptive cruise control. This newly juiced system has the car automatically slow down for turns in the road ahead to help the driver steer safely through. It also comes with an updated lane-change assist, meant to make the maneuver easier (and safer) for human drivers.

Some of this is helpful. During a test-drive, I was impressed by how well the S-Class handled funky road features like roundabouts and toll booths. But there are still parts of the semi-autonomous driving system that can be unsettling for drivers.

It points to the awkward challenge of sort-of self-driving systems: How do automakers notify the people behind the wheel when they, and not the machines, should take charge? And is there such a thing as too much information? It’s why well-crafted driver interfaces are so critical, providing steady awareness of what the vehicle is doing. The S-Class fixes most of the problems with Mercedes’ earlier systems, with crisp monitoring graphics that are easy to read and use. But like any growing child, the semi-autonomous vehicle has its own quirks.

Mercedes-Benz

Twisty Turns

Mercedes can credit some of the new S-Class breakthroughs to maps. “There are situations in the road ahead that neither cameras or sensors can see, but which the computer can prepare for by folding in map data,” says Mercedes engineer Bernhard Weidemann.

As a result, the vehicle can now automatically adjust its steering and speed based on the tortuous road up ahead. It will even modulate its approach based on your own strange driving preferences. Drivers can select one of three modes: in eco mode, you’ll get a more leisurely maneuver; in comfort mode, a faster turn; in sport mode, you’ll rocket through like Lewis Hamilton tackling a chicane at Monaco. The car also factors in downhill slopes by gently decelerating the vehicle, which should make otherwise leery semi-autonomous drivers a bit more chill about a robot making their turns for them. Now drivers won’t have to keep disengaging their cruise systems to deal with squiggly lines on the map. It makes for a relaxing drive, like playing a racing game with the assists turned on.

Adventures in Lane Changing

But the semi-autonomous cruise functions still aren’t perfect. Unlike a (good) human motorist, the car won’t wait for breaks in the traffic flow before entering roundabouts. And it won’t know to make a turn after pausing for a stop sign. This is, of course, a semi-autonomous driving system, which means it’s on the driver to monitor the vehicle and make sure it doesn’t do anything dumb.

The limitations extend to the S-Class’s updated lane changing feature. Once a driver tells the new car to change lanes, it will watch and wait for an ideal opening—for up to 10 seconds. The idea here is to nix the driver’s workload. The machine is better than you, Mercedes posits, so it will select the best time to shift lanes.

But this feature introduces the possibility that the driver might actually forget they’ve asked for a lane change, and be very surprised when the change starts happening 10 seconds later. Weidemann, the Mercedes engineer, scoffed at this—but it happened to me within an hour of being in the car.

Human brains are like that. We lose smartphones we’d been using seconds before and glasses sitting right on our noses. Semi-autonomous driving systems will have to get better at accommodating this everyday human dysfunction. If a robocar can get through a roundabout—the kind of driving move that flummoxes many Americans—a simple lane change maneuver shouldn’t be scary at all.