California's Department of Motor Vehicles has released new testing rules that will require Google to add manual controls to its driverless cars.

The rules, which will take effect starting Sept. 16, requires that drivers should have the option to take "immediate physical control" of a car running on public roads whenever needed. 

The new rules means that Google's driverless cars will need to have a steering wheel and pedals for the accelerator and brakes if the company aims to test the vehicles within the state of California.

Google could have chosen to test the driverless car prototype on private roads, or to test the vehicle in public roads outside of California. However, the company decided to comply with the state ruling instead.

Google will be adding a small steering wheel and a pedal system to the cars that the drivers could use while testing. The additions to the vehicles will be temporary.

"With these additions, our safety drivers can test the self-driving features, while having the ability to take control of the vehicle if necessary," said Courtney Hohne, a spokeswoman for Google.

Both Google and road safety regulators are treading carefully on the subject of driverless cars, and the new ruling shows just how far Google is from gaining wide acceptance for its project. 

Google Car Project director of safety Ron Medford had previously asked the California DMV to allow the company to test other kinds of driverless vehicles, such as trucks and motorcycles, but the state declined.

"We wanted to take baby steps in terms of testing and how technology is rolled out so we are capable of handling it and Californians accept it," said California DMV Deputy Director Bernard Soriano.

Google entered a new phase in the development of its driverless cars when it unveiled a prototype earlier in the year. The idea behind the vehicle is that passengers can simply choose a destination through Google Maps, press the Go button, and it will be the car's function to get the passengers there safely.

The prototype has no steering wheel and pedals, with a top speed of 25 mph.

"They won't have a steering wheel, accelerator pedal, or brake pedal ... because they don't need them," Google said. "Our software and sensors do all the work. The vehicles will be very basic -- we want to learn from them and adapt them as quickly as possible -- but they will take you where you want to go at the push of a button."