(Reuters) - Alphabet Inc’s Waymo said its fleet of self-driving vehicles logged more than 600,000 miles last year on public roads in California, while rival Tesla Inc reported operating autonomous vehicles for just 550 miles on public roads since last October, according to reports released on Wednesday by the state’s Department of Motor Vehicles.

The Waymo logo is displayed during the company's unveil of a self-driving Chrysler Pacifica minivan during the North American International Auto Show in Detroit, Michigan, U.S., January 8, 2017. REUTERS/Brendan McDermid

California requires auto companies and suppliers who test their self-driving vehicles on public roads to provide an annual compilation of miles traveled in autonomous mode and the number of “disengagements,” or times the self-driving system was deactivated and control handed back to humans because of a system failure or a traffic, weather or road situation that required human intervention.

Tesla Chief Executive Elon Musk has said the company plans to install new hardware and software to enable fully autonomous driving in Tesla vehicles before the end of the year. Tesla’s four self-driving test vehicles compiled 550 miles, with a disengagement every 3.5 miles.

Waymo, the former Google auto unit that was renamed last fall, operated a fleet of 60 autonomous vehicles last year on California roads. While increasing miles traveled by 50 percent, it said the number of self-driving disengagements fell by 75 percent to 124, an average of one every 5,000 miles.

“This is just more evidence of the gulf between Waymo and all other companies in terms of testing and execution of self-driving systems,” said Gartner analyst Mike Ramsey.

Automakers are testing autonomous vehicles in several states and on private tracks - activity that would not be covered by the California reporting requirement.

General Motors Co and its Cruise Automation affiliate logged nearly 10,000 miles in self-driving vehicles on California roads.

GM’s Cruise tested a fleet of electric vehicles, including 20 Chevrolet Bolts, equipped with self-driving systems, noting the number of disengagements fell as miles traveled increased in the latter half of the year. GM/Cruise averaged a disengagement every 50 miles.

Nissan Motor Co tested a fleet that included three Leafs and two Infiniti Q50 sedans, logging 4,000 miles with a disengagement every 150 miles.

Ford Motor Co and Daimler AG's Mercedes-Benz said their self-driving vehicles logged fewer than 1,000 miles each last year in California, while Honda Motor Co and Volkswagen AG VOWG_p.DE said they did not test self-driving vehicles on public roads in the state.

Besides California, three other states allow operation of self-driving vehicles on public roads and several others are considering similar legislation.