Alphabet's Waymo announced on Tuesday that it was expanding its commercial self-driving car service by adding 10 vehicles to Lyft's network in the Phoenix area "over the next few months." The small scale of the expansion is the latest sign that Waymo is deploying its technology at a more leisurely pace than most people—both inside and outside the company—were expecting a year ago.

Waymo has long been seen as having a significant head start on self-driving technology. In 2018, the company aimed to capitalize on its early lead by launching a commercial self-driving service by year's end. It arguably met that goal last December, but only under generous definitions of "commercial" and "self-driving."

The new Waymo One service was not open to the general public—it was initially limited to a few hundred people who had previously participated in Waymo's closed testing program. And after months of talking up fully driverless technology—including a TV commercial starring late-night host Jimmy Kimmel—every Waymo One vehicle had a driver behind the wheel.

Obviously, no one should fault Waymo for proceeding cautiously with a technology that could kill someone if it malfunctioned. Still, the limited launch of Waymo's initial service seemed like a sign that Waymo's technology wasn't actually ready for wide-scale commercial use.

Now, six months after that initial launch, Waymo says it is adding 10 Waymo vehicles to the Lyft network "over the next few months." Once the vehicles come online, customers whose routes fall into Waymo's service area—currently limited to a slice of the suburbs southeast of Phoenix—will be offered the option to ride a Waymo car (with a safety driver) instead of a regular human-driven car. Lyft has a similar partnership with Aptiv in Las Vegas.

It's interesting to compare the small scale of Waymo's rollout so far against the company's previously announced vehicle orders. Waymo ordered 500 Chrysler Pacifica minivans in 2017—on top of about 100 Pacificas the company already had at that point. Then last year, the company ordered an additional 62,000 Pacificas, as well as 20,000 Jaguar I-Paces.

Technically, Waymo didn't specify how long it would take to deliver all those vehicles—the company just said it would start using the I-Paces in 2020. So Waymo isn't technically behind schedule, but it will take a very long time for the company to roll out 82,000 cars if it does so 10 cars at a time.