CR's Tesla Model S, which now has Navigate on Autopilot

Consumer Reports put Tesla’s new Navigate on Autopilot system through its paces on Connecticut highways and found it to be technologically impressive, but our testers also had serious concerns about how the feature performed in real-world driving, especially in heavy traffic.

The feature can guide a car through highway interchanges and exits, and suggest and make lane changes. It’s now available in the U.S. for Tesla owners who have purchased Enhanced Autopilot. The automaker is calling the initial release a beta version.

CR downloaded the update to our Model S and tried the feature out on the public roads near our Auto Test Center in Colchester, Conn. 

While Navigate on Autopilot in no way transforms a Tesla into a self-driving car, it does offer a glimpse into what the future of vehicle autonomy might look like—including the potential problems.

Trying Navigate on Autopilot

How Navigate on Autopilot Works

Like most navigation systems, Navigate on Autopilot will suggest the lane that a driver should be in based on an upcoming exit, merge, or interchange. But Tesla's system takes it a step further, and the vehicle will automatically enter that recommended lane as long as the driver confirms the suggestion by engaging the turn signal or Autopilot stalk. The vehicle also must determine that it is safe to make the lane change.

More on Autonomous Driving

The car also will automatically take highway exits—without the driver activating the turn stalk—slow down on off-ramps, and merge into traffic after entering a highway from an on-ramp. Based on map data, the system will only work on highways, and warns drivers to take control when exiting a highway because the car can’t stop on its own at stop lights or stop signs.

“This system offers a glimpse of how autonomous cars might actually work in the future,” says Jake Fisher, director of auto testing at Consumer Reports. "Tesla is essentially demonstrating how self-driving technology could be used on the highway, while still requiring drivers to be in control everywhere else. A system like this might be employed in the not-so-distant future for the trucking industry and could be a huge convenience for someone taking a long trip."

Additionally, Navigate on Autopilot will make lane change suggestions to help the driver maintain a steady pace.

“If you have your adaptive cruise control set to 75 mph and you have a car in front of you that’s only going 65, it’ll suggest to you to go in the next lane and pass,” Fisher says. “Then, it executes the lane change for you if you engage your turn signal.”

However, Navigate on Autopilot does not suggest drivers return to their original lane after passing a slower vehicle. “If you only listen to the system, you’ll be the world’s worst left-lane hog,” Fisher says. A Tesla spokesperson told CR that future versions of the system will suggest that drivers return to their original lane.

Navigate on Autopilot display

Room to Improve

We also encountered other issues that concern us. The Navigate on Autopilot system occasionally recommended that the driver initiate a passing maneuver that would cut off a faster-moving vehicle coming up alongside—a common situation that drivers might encounter when stuck behind a slower vehicle.

Although Tesla currently requires the driver to engage the turn signal or Autopilot stalk to complete a suggested lane change, an inattentive driver might still follow the system's recommendation, putting the Tesla in the path of a fast-approaching vehicle.

Tesla says that future versions of Navigate on Autopilot will allow the car to automatically make lane changes without driver confirmation. A company spokesperson told CR that these future versions will use three rear-facing cameras that can detect fast-approaching objects “better than the average driver.”

More on Autonomous Driving

As the system currently stands, CR’s testers found it lagged behind their own skills while driving in heavy traffic. "Overall it works best in easy situations with minimal traffic,” Fisher says. “But as the traffic builds, it clearly displays the limitations of today's technology."

The system also had issues navigating interchanges: Not far before exiting a congested highway, the system recommended that the driver change lanes to pass a slower-moving truck instead of waiting to exit as most drivers would choose. But traffic was too heavy for the Tesla to complete the pass. Autopilot slowed the car considerably so it could drop back behind the truck and into the exit lane—which slowed traffic in the process.

Tesla told us that its feature relies on many factors, including “the speed of the cars in your lane, the speed of the cars in the adjacent lane, the density of the cars in the adjacent lane, and the amount of time the car has to complete the lane change before the next route transition.” In certain “unlikely” situations, it might even slow the car to a complete stop, the Tesla spokesperson said.

“It was able to execute the exit, but it wasn’t pretty,” Fisher says. “It didn’t have the foresight to say, ‘With all this traffic, passing so close to the exit is not a smart thing.’”

Tesla's Navigate on Autopilot touch screen

Given the issues we identified, CR is pleased to see that Tesla has taken a somewhat cautious approach as they roll out this new feature.

“When you first turn the feature on, there’s a big warning screen,” Fisher says. “Even when you enable it, you have to acknowledge multiple prompts that remind the driver that the feature isn’t a substitute for paying attention.”

Tesla says that Navigate on Autopilot also acts as a testbed for automakers' continuing research into vehicle autonomy. “As more miles are collected with Navigate on Autopilot in use, we will continue to make it even more capable and efficient,” the company said in a blog post announcing the feature.

Overall, while Navigate on Autopilot may be an interesting technological achievement, it also has major limitations.

“Tesla owners who use this system get to see what the future might hold,” Fisher says. “But it also demonstrates the many challenges automakers face in bringing autonomy to vehicles.”