Google and Fiat Chrysler have officially announced that they're teaming up to build 100 2017 Pacifica minivans with plug-in hybrid drivetrains that will become part of Google's growing fleet of self-driving test vehicles. Currently, the fleet contains Lexus RX crossovers and Google's own prototypes; the Pacificas will mark the third vehicle type to come into service, which is expected to be in testing by the end of this year. When they're built, it'll more than double the size of Google's fleet. News of the impending deal was reported this morning by Bloomberg.

Adding a minivan to the fleet marks the first time that Google has had access to a real shuttle — a vehicle that could be used to move a good number of people with a self-driving car at once. (The Pacifica can hold up to 8 passengers.) That's likely seen within Google as an important step to bringing self-driving technology to market, which will almost certainly become a goal in 2016 as the project spins out of Google's X laboratory.

The Pacificas will have custom modifications made by FCA, which will then be handed over to Google to have autonomous hardware and software fitted. (This is a level beyond the Lexus RX, which Google retrofitted without a manufacturing partnership with Lexus or Toyota.) The companies will be co-staffing a facility in Michigan, near FCA's US headquarters, to engineer the vehicles.

Google isn't saying whether this is a one-off deal or part of a broader partnership that could eventually have commercial implications, but we do know that it's non-exclusive to both parties. This particular batch of minivans will be used exclusively for testing, which means there's no commercial service being launched today. If Google does indeed plan on eventually launching a self-driving ride-hail service — as has been reported — it probably won't be these particular Pacificas doing it.

It could also switch or add automakers to its fleet at any time. Google had previously been rumored to be talking to Ford about a similar deal, and in comments to USA Today, John Krafcik — CEO of the self-driving car project — said that "we're excited FCA will be the first we integrate with," and "we will be working with many different partners going forward."