May Mobility robotaxi based on the Toyota Sienna Autono-MaaS platform

Back in 2009 when Google GOOG established a team to develop automated driving systems (ADS) that would eventually become Waymo, the first test cars they used were Toyota Priuses. Over the next several years, the Prius became the first vehicle of choice for ADS developers before eventually being supplanted by the Lexus RX450h, Ford Fusion and the Chrysler Pacifica hybrid. The next addition to that list may well be the Toyota Sienna Autono-MaaS.

The common thread through all of the aforementioned vehicles is that they have hybrid electric powertrains and a variety of electrified systems such as steering and braking that would make it easier to implement automated driving. The hybrid systems were appealing to developers because the sensors and computers needed to make a vehicle drive itself consumed a lot of electrical power, as much as 4-kW. That was more than most conventional 12V electrical systems could provide. Hybrid vehicles could provide upwards of 100-kW.

Up until 2016, Google and other developers that needed vehicles for testing, would go down to a local dealer and buy a Toyota, Lexus or Ford hybrid one or two at a time. That was fine for doing basic R&D because they weren’t ready to deploy a fleet.

However, by 2016, the Google self-driving team was far enough along to start expanding its test program. After previously failing to strike partnership deals with several automakers, the Google team went back to Chrysler to try to arrange a fleet purchase of 100 of the new plug-in hybrid minivans. Knowing what Google intended to do with the vans, Chrysler struck a deal to have its engineers collaborate with Google’s engineers to ease the hardware integration process. Chrysler developed a bespoke version of the wiring harness to support all of the sensors and computers that Google would be installing. That wiring harness and other modifications were incorporated on the regular Pacifica assembly line and the vans were delivered to the unit now renamed Waymo in something closer to plug-and-play form.

Over time, additional changes were made to the minivan including fully redundant steering and braking systems and power supplies. A couple of years after the first Waymo Pacifica debuted at the 2017 North American International Auto Show in Detroit, Chrysler had learned a lot about the vehicle requirements for ADS. Another ADS company that had switched to the Pacifica from the Ford Fusion hybrid told me in 2019 that Chrysler was offering a fully supported AV-ready version of the Pacifica to developers that made installation of the ADS much simpler. Those have been used by companies including Voyage, Motional, Aurora and China’s AutoX among others.

Unfortunately, despite many inquiries from me, Chrysler officials would never speak on the record about the AV-ready Pacifica hybrid. Many ADS companies continue to run the Chrysler vans, but just as the consumer minivan has competition, so does the AV model with a new entry from Toyota. The new Sienna Autono-MaaS is specifically configured for exactly this purpose.

In addition to control interfaces and new wiring harnesses, Toyota technicians install a new center ... [+] console in the Sienna Autono-MaaS to accommodate the computers required for automated driving

The fourth-generation Sienna debuted as a 2021 model exclusively with a hybrid powertrain, one of several recent Toyota vehicles that comes only with electrification. The combination of the high voltage electrical system and the minivan form factor, makes the Sienna, like the Pacifica before it, a great choice as a development platform for both robotaxi and automated delivery vehicle applications. The Sienna is built exclusively at Toyota’s Princeton, Indiana assembly plant and those destined for the Autono-MaaS conversion are then shipped to the automaker’s technical center in York Township, Mich.

The technicians at the prototype build facility there make a number of modifications to prepare it for its new use case. Modified brake and steering systems are installed that feature redundant actuators that are needed to ensure fail operational capability when the van is operating without a human driver. A new wiring harness with redundant power and control interfaces that allow the ADS to manage propulsion, braking and steering are also added. A new center console is installed with a rack for installation of the computer system for the ADS.

Aurora Innovation robotaxi prototype based on Toyota Sienna Autono-MaaS platform

Toyota technicians also install the cabin awareness system in the headliner. This system uses a Vayyar imaging radar sensor to monitor all of the seating positions to know where passengers are, when they are buckled in and it can even tell if they are breathing.

All of this along with the customer technical support provided by Toyota, makes it a lot easier to get started with ADS development than it was a decade ago when startups had to figure out where to cut into the wiring harness of a Prius.

There are now 40 Siennas operating in the May Mobility and Aurora Innovations test fleets in several cities across the U.S. Another 20 have been built and are ready for delivery for anyone that needs them in relatively short order. Beyond that Toyota executive program manager Beth Loomis expects about a three month lead time from order to delivery. Toyota is also studying how in the future when customers are potentially ordering and deploying thousands of these vehicles, the modifications can be incorporated into the Toyota production system at the factory. However, that work is likely still several years in the future.

For now, Toyota isn’t giving a specific price tag for the Sienna Autono-MaaS, but Loomis acknowledged that it is roughly double the base vehicle. So depending on the trim level used, it’s probably about $75,000 to $80,000 which is not a bad deal when compared to what it would cost a developer to make these modifications on a custom basis. Plus a custom modified van wouldn’t get technical support from Toyota.