Google may have hoped to wade gently into the ride-hailing waters jealously guarded by San Francisco's Uber and Lyft, but news today that its Waze-based carpool app will be expanding to San Francisco is threatening to make a serious splash. The Wall Street Journal writes that the expansion could "portend a clash," particularly with Uber, a company valued at $68 billion in which Google once invested $258 million.

Google dipped a toe into matters with its carpooling service this May, launching a small pilot program based around its Mountain View headquarters called Waze Rider. The service stems from the Israeli traffic-reporting maps app, Waze, that Google bought in 2013. Waze Rider somewhat informally began to pair existing Waze users with similar driving destinations, encouraging them to ride together, either for no charge or for a small reimbursement fee, of which Google wasn't asking for a cut.

In the coming San Francisco Waze Rider pilot program, any and all Waze users can sign up as drivers, no vetting necessary. However, passengers must be employees of a group of specific local companies, including Adobe and Wal-Mart, headed to a particular set of offices. Their numbers will be capped at 25,000 and they'll also be limited to just two rides a day — i.e. to and from work.

The initial competitive advantage of Google's Waze is price — free is pretty cheap — but its focus is, for now, incredibly narrow. It's still possible the company will face unforeseen obstacles as it enters the new space. “I don’t think they’ve had any significant experience in a lot of the issues that will surely arise around [Waze Rider]" one analyst, Ben Schachter, tells the Journal.

The coming era of driverless cars is where the calculus becomes particularly complex. Pedal to the metal, Uber is debuting autonomous vehicle service for customers in Pittsburgh, PA, in just weeks (what could go wrong?!) while Google is gearing up to be a key player in the field with its own cars. Those plus Waze Rider could promise a completely new way and inexpensive way to get around.

Waze, which operates as a separate unit within Google (a company itself enveloped in the larger Alphabet Inc. network of companies) has 65 million active users. Its draws are the ability to report — and see live reports of — traffic accidents or other changes. Some of the most loyal users of Waze? Why, Uber and Lyft drivers, of course.

Previously: Google-Owned Waze Gets In The Ride-Hail Game, Launches New Carpooling App