Alphabet's (GOOGL) - Get Report(GOOG) - Get Report self-driving car unit Waymo is arguably the most advanced autonomous vehicle program in the world. 

Some may say that distinction belongs to Tesla (TSLA) - Get Report , while others will say that General Motors' (GM) - Get Report Cruise unit, Nvidia (NVDA) - Get Report or some other company is farther along. At the end of the day, though, Waymo has one of the only, and quite easily, the most impressive commercial mobility-as-a-service platforms on the street today.

Currently, that program operates near Phoenix, Ariz., while Waymo preps for further expansion -- which comes in multiple forms.

On the one hand, Waymo wants to build out its autonomous taxi service (known as Waymo One) to more cities. That's obviously throughout the U.S., but also includes Europe at some point and likely Asia as well. But expansion goes further than MaaS; it also includes semi trucks.

When you think about the big picture with autonomous driving, it's a lot more than just getting a kid home from the mall or a bar patron home safely from a night out on the town. It's also more than a simple taxi-replacement service.

When considering the transportation market as a whole, it's a massive industry stretching from cars to planes to semi trucks. So it's only natural that if Waymo is working on autonomous vehicles to get people from point A to point B, that it will do the same thing for products as well. And given that the company already operates its main service in Arizona, it makes sense to add its big rigs back to the picture.

Waymo began testing autonomous class 8 trucks in Arizona in 2017, but stopped last year. Since then, observers have seen them on the roads in San Francisco and Atlanta.

Waymo will reportedly start testing them again on Arizona roads, both with freight and without freight. The vehicles will also feature two safety drivers in the event a human needs to take over for the system. As of now -- and with no surprise, just like its Waymo One service -- the company will not operate commercially for the time being.

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Waymo's autonomous driving taxi.

When I attended the Autonomous Vehicles conference in Detroit, MI. last summer, the trucking industry was upbeat about the future of self-driving trucking solutions. Not only would it increase safety, but it should help alleviate driver shortage and improve efficiency. Tackling the latter allows companies to cut down costs, too.

Further, a number of trucking routes in the U.S. would allow for level 4 or level 5 autonomous solutions. For instance, Las Vegas to Los Angeles or L.A. to Phoenix allows for relatively smooth autonomous testing -- assuming you're not talking about going into the heart of the city. Rather, these companies would likely use warehouses outside of the city for autonomous shipments.

It makes perfect sense for Waymo to go in this direction and Arizona is a perfect test zone. The company continues to expand its ambitious self-driving program in new directions and adding semi trucks to the mix will only up the potential value for Waymo (and ultimately Alphabet) in the future.

This article is commentary by an independent contributor. At the time of publication, the author had no positions in the stocks mentioned.