Ridesharing platforms Lyft and Uber are hot today. Driverless cars are the hot stuff of tomorrow. And General Motors (NYSE: GM) wants in on both. The company just took a $500 million stake in Lyft, in part to develop a fleet of driverless taxis.

GM clearly thinks it's a worthwhile investment, and others agree. Rumors abound that Ford (NYSE: F) is going to launch a similar partnership with Google parent Alphabet (NASDAQ: GOOGL).

It could be just an expensive trip to nowhere, but the signs seem to be pointing toward big money -- if GM and Ford can hang on to it.

The nuts and bolts

According to GM, the goals of the partnership are as follows:

Autonomous On-Demand Network: The joint development of a network of on-demand autonomous vehicles.

Rental Hub: Beginning immediately, GM will become a preferred provider of short-term use vehicles to Lyft drivers through rental hubs in various cities in the U.S.

Connectivity: Lyft drivers and customers will have access to GM's wide portfolio of cars and OnStar services.

Joint Mobility Offerings: GM and Lyft will also provide each other's customers with personalized mobility services and experiences.

Right now, GM is going to start offering rental vehicles to Lyft drivers in select cities. Down the line, the companies envision a Lyft without drivers: just on-call fleets of autonomous taxis taking riders where they want to go.

It's not hard to see the advantages for GM or Lyft. GM would be able to park fleets of Lyft vehicles at their dealerships across the country, which could earn revenue for the company even when they're not being shown or test-driven. Also, if you're looking to buy a driverless car, you may be more likely to buy a model you've already ridden in. Lyft, of course, would benefit by not having to pay drivers.

GM has clearly seen the writing on the wall: Vehicle ownership and operation are probably going to look different in a couple of decades. CEO Mary Barra admitted as much in an interview with Vanity Fair: "We want to ... make sure we're in the lead of redefining personal transportation in the future. Rest assured, we have lots of work to do."

The secret sauce

Unlike GM and Lyft, which have been very public with their partnership plans, Ford and Google are playing coy. Despite numerous reports that Ford would announce the partnership at the 2016 Consumer Electronics Show, nothing materialized.

The following week, at the North American International Auto Show in Detroit, Ford CEO Mark Fields didn't say yes...but he didn't say no, either. "Listen ... We talk with a lot of different companies, we work with a lot of different companies," he said. "But I think as you can respect, those discussions are private with any companies, and we're not going to comment on the speculation."

As one of the pioneers of driverless cars, Google would be a formidable partner for any automaker interested in the technology...and a formidable foe for competitors -- competitors that may soon include Lyft and Uber. According to Bloomberg, Google not only plans to launch a taxi service using its fleet of autonomous vehicles this year, but will make it a stand-alone business under the Alphabet umbrella.

Meanwhile, Ford isn't just relying on a potential Google partnership. The company recently announced it was tripling its fleet of autonomous Ford Fusions to 30, which it claims will give it the largest driverless fleet of any automaker.

The driverless arms race

At this point, it would be shortsighted for any car company to ignore driverless technology. And car companies like Ford and GM are looking to get a leg up on their numerous competitors in whatever way they can. Partnerships with ride-sharing or tech companies are a means to that end.

Another means is filing driverless patents at record rates. According to a report by Reuters, Toyota holds far and away the most patents related to autonomous vehicles, with more than 1,400, over twice as many as its nearest American competitor, GM. Google, which has the most driverless patents of any tech company, is in a paltry 26th place on Reuters' list, behind many automotive companies.

But having the most patents won't necessarily yield the best or the dominant technology. And right now, it's unclear from where that technology will come. Possibly from a tech company like Google, Tesla, or Apple. Or maybe from a German car company like BMW, Audi, or Daimler, which formed a consortium in August to purchase Nokia's mapping unit to help develop digital mapping for autonomous vehicles.

The Foolish bottom line

GM, Ford, and Google are all wise to pursue deals and technology advances that will make driverless cars -- as commercial or personal vehicles -- a reality. But with such a fragmented landscape and no clear dominant technology, buying any company based on its plans to offer autonomous vehicles would be speculative at best. Investors should instead evaluate the companies based on their current offerings and near-term outlooks.