In my state (PA), ATV's and UTV's need to be registered. That does not mean you can drive it on the road other than perpendicular to the road to cross it.
That said, our local police won't bother you for driving on the road so long as you're not driving crazy. A possible exception is the major roads with high speed traffic.
Heck, in the summer, nearly half the traffic on my road is ATV's & UTV's.
So…you must rely upon an individual cop’s private opinion and munificence… Lotta cops have different opinions and viewpoints and depending on the argument held with their wife the night before might influence things.
In my state, the vehicle is required to meet certain regulations and cannot be operated on freeways or contrary to where minimum speed limits are posted. Otherwise, if it meets the definition of an agricultural or construction machine and complies with those regs…. the operator may count on the law to support him.… Of course, it cannot guarantee protection from idiot drivers on the road who seem to believe the road is only for them.
And the RTV does not have the protections afforded the occupants which otherwise may exist such as crashworthiness, airbags, fire-resistance, head-protection, crush-panels, etc etc.
I operate on back-country county roads where my neighbors are all farmers or are familiar with ag operations. Whenever a hot-rodder comes barreling down the road I pull off to the side and let ‘em pass.