The self-driving technology has forward radar, a forward-looking camera, and an array of ultrasonic sensors that shoot out radio waves up to 16 feet around the car to detect other vehicles or objects on the road, reported the Wall Street Journal.
Tesla had a driver take the vehicle on part of Interstate 405 near Los Angeles International Airport to map out the road for the autopilot.
Musk complained that the lane markings were angled in different directions, which confused the autopilot software, noted The Washington Post.
"We really need better lane markings in California. This is crazy," Musk said. "If we were in Germany or Japan or China this would be great -- it would be easy because we can actually see clear lane markings."
Musk referred to the photo below of a stretch of Interstate 405.
"Normally you can exclude sort of strange figments on the road, like skid marks, whatever because they're not where the lane is," Musk stated. "But in this case you have the true lane position and the sort of fake-lane position, and they're diverging. The camera system would then follow the diverging system and go into the wrong lane."
Tesla advised drivers to keep their hands on the steering wheel and to be prepared to take hold of the wheel when in autopilot mode.
"We still think of it as a sort of public beta," Musk said. "So we want people to be quite careful when using autopilot."