Yep, the majority of newer cars cannot be flat towed. For a Prius, that means a car carrier trailer (high cost and weight) - or - tow dolly.
The dolly is a very easy option. We have over 15,000miles towing our Ford Hybrid (basically a mod'd Toyota Hybrid system). The EZE-tow was our choice, but all the major brands are good.
Your car will be very happy and safe up on the dolly, free of the miles added to the car's lower driveline and free of the risk of rock strikes like so common for flat towed cars.
Just load the car, cinch the tire straps, hook the safety chains and go (parking brake released, of course). We load and unload in about the same or less time with our travel partners who flat tow. Our dolly has built-in brakes and there's lights on most all dollies, so no mods to the car at all.
There's 2 point to know about dolly towing:
1. Where to put the dolly when stopped? If you must disconnect the dolly (rare on a Class C due to size) just slide it under the RV's rear overhang (you can get a caster for the tongue to make that super easy).
2. Getting under the car for loading/unloading? There is NO NEED to get under the car. If safety chain hook-up does not have an easy spot on the Prius, just add a loop of chain or steel cable to a hard point on the car, which is easy to access.
Just like flat-towing, always wear gloves to protect your hands while loading/unloading...and stop to check the hook-up a short distance after departure and at every stop.
If there is any question about dolly or trailer towing, why not test it with equipment rented from U-Haul? We did this 3 times just to be sure before purchasing anything for towing.
Kim and Steve, Mustang LCDR (Ret), '07 Damon Outlaw #1193
I have seen gross intolerance shown in support of tolerance, Samuel Coleridge
WE LOVE OUR OUTLAW RV