Chevy Bolts with self-driving systems have been spotted in San Francisco recently. GM's self-driving tech is thought to be quite advanced, but GM says it is still a long way from market. Image source: General Motors.

When will General Motors (GM 1.98%) have cars with self-driving technology for sale?

The answer seems to be "not soon." While GM is increasingly perceived as a leader in the technology, and had originally promised to have a limited system on the market later the year, it has since delayed that system indefinitely. 

Probably mindful of the controversy around Tesla Motors' (TSLA -3.40%) Autopilot system, GM executives want to make absolutely sure that its technology is proven safe before it comes to market.

That could turn out to be a longer process than many investors have been expecting. 

GM is being vague about the timing for good reasons

CEO Mary Barra made it clear during GM's second-quarter earnings call: GM is aggressively developing self-driving technology, but it won't rush the systems to market.  

"We haven't announced the exact timing [when GM will bring self-driving features to market] because as we develop the technology, we're being gated by making sure that we have safe autonomous technology to put into the marketplace," Barra said. 

Barra noted that GM's investment in Lyft will give it the opportunity to test and prove its self-driving technology in a way that allows members of the public to experience it before they can buy it. But, she said, there will be a human "safety driver" in the self-driving cars it uses with Lyft, at least for the time being.

Proving the technology will be a matter of racking up miles and time with the system, Barra said. "But we haven't put specific timing or quantities [of miles] on that," she said, 

GM's first system will be much more restricted than Autopilot

While it's not clear when GM will release a full-blown self-driving system, it is clear that it will carefully bring the technology to market in small steps. 

GM's first semi-autonomous system is called Super Cruise. It's similar to Tesla's Autopilot, but there are much stricter limits on how and when it can be used. In its initial form, Super Cruise will only switch on when the car is on certain highways that GM has carefully mapped. Lights on the car's steering wheel will tell the driver when the system is available. 

And because the system requires that the driver be ready to take over at all times, it will scan the driver's eyes to make sure that he or she is awake and paying attention. If not, the system will trigger an alarm.

GM has said that its first vehicle to be offered with Super Cruise will be the big Cadillac CT6 sedan. The rollout of Super Cruise on the CT6 was originally scheduled for later this year, but it has been delayed indefinitely. 

"We'll put it out there when it's ready," GM global product chief Mark Reuss recently told the Detroit Free Press. 

Why GM has to be more conservative than Tesla

In the wake of a fatal accident in May in which Tesla's Autopilot was engaged, Consumer Reports called on Tesla to disable the Autopilot system in customers' cars until it can update the Autopilot software to ensure that the driver's hands are on the steering wheel. 

Tesla has argued that despite its imperfections, Autopilot is already safer than a human driver in some circumstances -- and therefore, it doesn't think it's right to disable the system. 

There's merit to that argument, but I don't think GM could get away with making the same argument in the same circumstances. I suspect that GM knows that it will be held to a much more conservative standard than swashbuckling Tesla, and Barra clearly doesn't want to find herself having to make an argument like that -- or having to deal with calls from Consumer Reports to disable a new system intended to improve safety. 

Does that put GM at a disadvantage? Probably not in the longer term. It may not be first to market with a fully self-driving system. But it's clear now that GM will be among the first automakers to bring self-driving technology to market -- and it's also clear that GM will go to great lengths to ensure that whatever it offers is made as safe as possible.