Ride-hailing start-up Lyft has a big new investor: Alphabet (GOOG -1.80%) (GOOGL -1.82%). 

Lyft announced on Thursday that CapitalG, Alphabet's investment fund, is leading a $1 billion financing round for Lyft. The move follows an agreement made in May between Lyft and Alphabet's self-driving subsidiary Waymo to work together on the development of autonomous-vehicle technology.

It also follows a flurry of interest in Lyft by several automakers and tech companies working on self-driving technology of their own -- including General Motors (GM -0.91%), which made a big investment in Lyft last year.

The three men are shown standing arm-in-arm at Lyft's headquarters.

Lyft co-founders Logan Green (left) and John Zimmer (right) with CapitalG partner David Lawlee (center). Alphabet's CapitalG fund is leading a $1 billion investment round in the ride-hailing company. Lawlee will join Lyft's board of directors. Image source: Lyft. 

What we know about Lyft's latest funding round

We don't know a whole lot yet. Lyft announced that CapitalG led the round, that the total investment in Lyft is $1 billion, that CapitalG partner David Lawlee will join Lyft's board, and that Lyft's post-round valuation will be $11 billion. Lyft was valued at $7.5 billion after its most recent funding round, in April. 

Lyft didn't name the other investors in this round. 

Johana Bhuiyan of Recode, who has followed Lyft closely, reported that this investment round wasn't driven by an urgent need for cash. Lyft has previously said that it expects to be profitable by next year. Why the investment now?

That's just one of a few reasons to think that there might be an interesting backstory here.

Alphabet has some good reasons to want to get closer to Lyft

For starters, consider that Waymo is locked in a fierce legal battle with Lyft arch-rival Uber Technologies. Waymo has alleged that a former employee stole key technology secrets related to self-driving when he left to form a new company; that company was acquired by Uber a few months later. 

Also consider that Waymo is racing to dominate the market for autonomous-vehicle systems, an emerging space with huge growth and profit potential. Ride-hailing is expected to be an important early market for self-driving vehicles, and Lyft could be a major customer. 

It's possible that Alphabet felt that it needed to make a big move to get out ahead of the self-driving rivals that already partnered with Lyft. Earlier this year, Lyft opened its service to automakers and tech companies that wish to test their prototype self-driving systems in real-world conditions serving Lyft customers. Besides Waymo, participants include:

It's possible that the move by Ford was one factor in Alphabet's decision to back up its interest in Lyft with a big investment. 

But there's another piece of this puzzle: What about GM?

Where does GM fit into this chess game?

Ford is a automotive heavyweight, but few expect the Blue Oval to be first to market with self-driving vehicles. It's a very different story with GM, which said last month that it has completed development work on a "mass-producible" Level 4 self-driving vehicle. 

GM, of course, invested $500 million in Lyft early last year at a $5.5 billion valuation, receiving what was then a 9% stake and a seat on Lyft's board that has been filled by GM president Dan Ammann. The idea seemed to be that GM would be Lyft's primary self-driving partner, but the relationship between the two seemed to sour earlier this year.

The three are standing with two Chevrolet Volt sedans.

Green (left) and Zimmer (right) with GM president Dan Amman last year, when GM made a $500 million investment in Lyft. Ammann is now a member of Lyft's board of directors. Image source: General Motors. 

GM has since hinted that it might develop its own ride-hailing service via its existing car-sharing subsidiary, Maven. It has also made other moves that suggest it now wants to own as many pieces of the mobility puzzle as it can, from self-driving sensor hardware to ride-hailing software and (perhaps significantly) the data it would gather while operating such a service.

That could make GM a big long-term rival to Waymo. It's probably far from the biggest consideration driving Alphabet's decision to invest in Lyft, but the search giant might think that its investment in Lyft (and its new seat on Lyft's board) could give it a better read on GM's plans and the state of its technology.

The upshot: At least Lyft won't run out of cash anytime soon

Whatever the motivations driving Alphabet's interest, it's a good time to be Lyft. Reuters reported last month that Lyft has been taking steps toward an initial public offering in 2018. If so, we'll know much more about Lyft's partners and intentions before long.