Google is quickly expanding its fleet of self-driving cars. The number of cars Google is permitted to drive on California streets has more than tripled in the last four months, says a report from Computer World.

Google's Self-Driving Car Fleet Rises Three-Fold In 4 Months

Expanding its small car fleet

According to California’s Department of Motor Vehicles records, Google had secured licenses for 73 self-driving vehicles through Monday, while in mid-May, it had licenses for only 23 cars. State law requires all companies that wish to test autonomous vehicle technology on public roads to obtain a permit from the DMV for each vehicle.

All the expansion in Google’s fleet is for its small, rounded car that has a laser imaging sensor on its roof. The car has a top speed of 25 miles per hour. Google obtained licenses for 50 such vehicles, but only a few are on public roads currently, the report says. These vehicles can be seen driving close to the offices of Google X in Mountain View.

Google’s remaining fleet of self-driving cars includes the previous generation Lexus RX450h SUVs. These cars are more industrial and have sensors on the sides and front. Similar to the small cars, the Lexus’ roof is also equipped with a laser imaging system.

Google way ahead of rivals

Tesla has the second-biggest fleet of cars after Google. Presently, the EV firm has 12 licensed cars and has been testing an autonomous driving mode for use on highways. Mercedes has a license for five cars, and licenses for two cars each are owned by Volkswagen, Delphi, Bosch, Nissan and Cruise Automation. Honda and BMW have one autonomous car each licensed in the state, according to the DMV.

California also requires drivers to get special licenses for autonomous vehicles, and Google is well ahead of rivals in this area as well with 219 licensed drivers out of 344 in the state.

Google previously reported that its driverless cars are averaging about 10,000 miles per week on public roads. Google’s cars have been involved in a handful of accidents, but none of them have been attributed to the company’s software, the Internet firm claims. The company informed consumers and investors that in all of the reported cases, the accidents took place when the cars were either under manual control or due to the fault of the other driver.