SAN FRANCISCO, July 31 (Reuters) - A Tesla Model S car

was in "Full Self-Driving" mode when it hit and killed a

28-year-old motorcyclist in the Seattle area in April, police

said, making it at least the second accident involving the

technology on which Tesla CEO Elon Musk is pinning his hopes.

The 56-year-old driver was arrested on suspicion of

vehicular homicide based on his admission that he was looking at

his cell phone while using the driver assistant feature, the

police said in a statement.

Tesla says its "Full Self-Driving (Supervised)" software

requires active driver supervision and does not make vehicles

autonomous.

Previously, the National Highway Traffic Safety

Administration (NHTSA) said there was one fatal accident

involving a Tesla vehicle using FSD software between August 2022

and August 2023.

That case remains under investigation, but experts say there

are limitations to Tesla's technology dependent on cameras and

artificial intelligence. Tesla's rivals such as Alphabet's Waymo

also uses expensive sensors like lidars to detect the driving

environment.

"There are so many things that can go wrong" with

Tesla's camera-only system, said Guidehouse Insights analyst Sam

Abuelsamid. For instance, he said it can inaccurately measure

how far away an object is.

"It is extremely challenging to collect and curate data

from all sorts of real-world elements such as motorcycles and

bicycles in the bread range of possible weather, lightning, road

and traffic conditions," said Raj Rajkumar, a professor of

electrical and computer engineering at Carnegie Mellon

University.

This year, Musk shelved Tesla's all-new affordable cars and

increased his bets on self-driving vehicles, saying he will be

shocked if Tesla cannot achieve full self-driving capability

next year.

Speaking in an interview with the Tesla Owners of Silicon

Valley club last weekend, he said a future vehicle will be like

a "tiny mobile lounge" where drivers will be able to watch

movies, play video games, work and even drink and sleep.

Musk has been aiming to achieve self-driving capability for

several years, with the technology under growing regulatory and

legal scrutiny.

The regulator began a probe of Autopilot in August 2021

after identifying more than a dozen crashes in which Tesla

vehicles had hit stationary emergency vehicles, and reviewed

hundreds of crashes involving Autopilot.

In December 2023, Tesla was forced to recall nearly all its

vehicles on U.S. roads to add safeguards to the software.