Cruise, the driverless car startup that's now a subsidiary of General Motors, has announced plans to launch a fully driverless taxi service by the end of next year. But a new report from The Information suggests that the company still needs to make a lot of progress to hit this ambitious target.

In recent months, Cruise has been ramping up testing efforts in a roughly 20-square-mile area in and around downtown San Francisco. Sources familiar with that testing effort told The Information's Amir Efrati that Cruise vehicles still had significant limitations.

"Cruise cars frequently swerve and hesitate," Efrati reports. "They sometimes slow down or stop if they see a bush on the side of a street or a lane-dividing pole, mistaking it for an object in their path." In one case, Efrati says, Cruise employees trimmed a bush ahead of a demonstration for journalists to make sure the car wouldn't swerve while driving past it.

Cruise employees have the option of riding in Cruise vehicles as they travel around San Francisco, but there's a big downside to doing so: self-driving car rides are often slower than a ride in a human vehicle—sometimes as much as 10 to 20 minutes slower. A big reason for that: "some San Francisco intersections and streets are 'blacklisted,' in some cases temporarily, and the cars must take circuitous routes around them."

An intersection might be blacklisted because its traffic light is too faint, because it has a complex roundabout, or because it requires a difficult lane merge.

According to the report, Cruise vehicles "can't easily handle two-way residential streets that only have room for one car to pass at a time. That's because Cruise cars treat the street as one lane and always prefer to be in the center of a lane, and oncoming traffic causes the cars to stop."

Other situations that give Cruise vehicles trouble:

Distinguishing between motorcycles and bicycles

Entering tunnels, which can interfere with the cars' GPS sensors

U-turns

Construction zones

Cruise is tackling some of the nation’s most challenging roads

A GM spokesman declined to discuss Efrati's reporting on the record but referred us to an October blog post by CEO Kyle Vogt explaining why Cruise has chosen to focus on testing in the complex driving environment of San Francisco.

"Our vehicles encounter challenging (and often absurd) situations up to 46 times more often than other places self-driving cars are tested," Vogt wrote. It was a not very subtle dig at the industry leader, Waymo, which has focused on testing its cars on the much less-challenging streets of the Phoenix suburbs.

"Testing in the hardest places first means we'll get to scale faster than starting with the easier ones," Vogt argued.

In other words, the limitations outlined in Efrati's reporting might simply reflect that Cruise has chosen to focus on an unusually challenging driving environment—not a sign that Cruise engineers are making notably slow progress.

That argument makes perfect sense, but it still leaves a big question about whether Cruise can achieve the goal of launching a commercial taxi service next year. Waymo's driverless cars were able to navigate most road conditions way back in 2015. But the company spent two more years on additional testing before it felt confident that it could respond safely in every possible situation its cars might encounter.