July 17 (Reuters) - Alphabet's Waymo is

expanding its service in Austin, Texas, to 90 square miles from

37 square miles earlier, the software giant's self-driving unit

said on Thursday, seeking to protect its top position in the

city from rivals such as Tesla.

Waymo, which has over 100 vehicles on the Uber ( UBER )

platform in Austin, will now cover new neighborhoods such as

Crestview, Windsor Park, Sunset Valley and Franklin Park, the

company said.

After cautiously expanding its self-driving taxi services

across the U.S. for years, Waymo is now largely seen as the

frontrunner in the space. It has about 1,500 vehicles across San

Francisco and other Bay Area cities, Los Angeles, Phoenix,

Atlanta and others.

Rival Tesla is looking to catch up, having

conducted a small trial last month of about a dozen of its Model

Y SUVs in a limited area of Austin.

But Tesla still faces a steep challenge to commercialize

this technology on a large scale and clear regulatory hurdles.

The automaker also does not use sensors such as radar and

lidar like Waymo and most rivals; instead, it depends solely on

cameras and artificial intelligence.

"Austin remains one of the fastest growing cities in the

country, and we are doing our part to grow with it," Shweta

Shrivastava, the senior director of product management at Waymo,

said.

Earlier this week, Waymo's vehicles logged a milestone of

100 million miles driven without a human behind the wheel,

doubling its mileage in about six months.