Odd-looking contraption. I wonder how it performs in the air. I also wonder why they didn't make it a three-wheeler and call it a motorcycle. You think there would be advantages from both the weight and regulatory standpoints if they went that way.
But even as a car, I don't think getting the DOT approval would be that big a deal. I think there's a category for "Limited Use Automobiles" or some such thing, with less stringent safety requirements. I know New York State has such a category for registration purposes. I also wouldn't be too surprised if the company could wring some exemptions from DOT for something as specialized as this.
Given that the TF appears to have a max speed of 65 mph on the ground, and given that even the most minor accident would likely cost thousands upon thousands of dollars to fix, I don't think the company figures that people will be using it as a primary car. I know I would be afraid to drive it on the LIE, for example, or even to park it on the street in most places.
There's also the question of whether all repairs must be performed by an FAA certificated Mechanic or Repairman-LSA. Where does the car end and the airplane begin? I guess the engine that drives the wheels would belong to the "car" part, and the one that drives the prop would belong to the "airplane" part. But what about the airframe, electrical system, and other common parts?
If they're marketing it to Sport Pilots, that would also limit its usefulness. Someone couldn't use it, for example, to fly somewhere for a business trip, and then drive the last leg. The SP Rule prohibits flying for any business-related purpose. I don't think there's any exception when the flying is "incidental" to that purpose, as there is with PP. To the best of my knowledge, an SP can't even fly to commute to work unless he's a CFI-LS flying to an airport to conduct instruction.
In short, I can't help but think there are more arguments against owning something like the TF than there are arguments in favor of it. I guess someone who lives a few miles from a small airport, but who doesn't want to pay for a hangar, could park it in their own garage or carport and drive to the airport when they want to fly, and it would be somewhat more convenient than trailering it. But other than that, I'm hard-pressed to find any practical advantage.
-Rich