Mercedes, the third-biggest producer of premium cars received a newly required license from California to conduct tests in daily traffic, the Stuttgart, Germany-based manufacturer said in a statement. The announcement comes two days after Audi, the second-largest luxury carmaker, said it received the first such permit in the state.

Eight-lane highways, traffic lights on the far side of an intersection and all-way stop signs are "all situations which do not exist in this form in Germany," said Axel Gern, head of autonomous driving research for Mercedes in North America. "We need to teach our research vehicles these situations."

California regulations require each testing vehicle to be backed by at least $5 million of insurance coverage, according to Ingolstadt, Germany-based Audi. The effort is necessary to test the technology and prove to regulators and consumers that it's safe. Part of the push includes showing that the computer systems are secure.