General Motors Co’s self-driving unit, Cruise Automation, told California regulators its vehicles were involved in six crashes in the state in September, but said none of automated vehicles were responsible. The accidents did not result in any injuries or serious damage, according to the GM reports, but did demonstrate the challenges for developers of self-driving cars confronted by crowded urban streets.A U.S. Senate panel on Wednesday approved legislation that would allow auto makers to greatly expand testing of self-driving cars. Some safety groups have objected to the proposal, saying it gives too much latitude to automakers.