By Abhirup Roy and Akash Sriram

Amazon.com Inc's self-driving vehicle unit Zoox has grown its headcount by about 16% at a time when access to capital is tight and other large companies have exited the autonomous driving sector.

Amazon's shares were 1.2% higher at $128.84 in early afternoon trading.

Based in California, Zoox, has ramped up its efforts to test its driverless robotaxi on pubic roads of Las Vegas since June 16, where the autonomous vehicle without a steering wheel or pedals has been driving itself around with the company's employees.

Zoox's headcount has grown to about 2,200, up from 1,900 at the beginning of the year, Chief Technology Officer Jesse Levinson told Reuters.

Levinson said that Zoox autonomous vehicle will not be driving on the Vegas strip yet but is being tested for handling traffic lights, intersections and drive at speeds of up to 35 miles per hour.

It follows approval from the Nevada Department of Motor Vehicles that authorizes Zoox to test drive its robotaxis on public roads in the state.

The company also intends to invest in its Vegas facilities, adding warehouse spaces to house its testing and robotaxi fleets.

"We are preparing for commercial launch and so it is important to beef up," Levinson said, adding that the company expects to maintain a similar growth rate in headcount throughout the year.

This comes at a time when the sector has been struggling with the development of fully autonomous vehicles due to constrained access to funding and an uncertain economy.

Ford Motor Co and Volkswagen AG last fall announced that they would shut down their Argo AI self-driving unit and focus on driver-assistance technology that provided more immediate returns.

Alphabet's self-driving technology project Waymo laid off 137 employees in a second round of job cuts this year.

(Reporting by Abhirup Roy in San Francisco and Akash Sriram in Bengaluru; Editing by Shweta Agarwal)