I think it might be more of a wording issue and combined with a number of changes within a few years of each other makes things a little more complicated as well. I think a year or two before they also had the new regulations for 3 wheel bikes and the testing and what kind of license you need. If I remember correctly it depends on how far apart the wheels are…so smaller ones just motorcycle license and large ones a car license.
I think there were also changes these past few years with regards to those with disabilities although I’m not familiar with those rules or changes.
It would be nice if the wording was made…simpler and classifications made clearer.
I think a Class/Level # would be easier instead of just using names.
Class 1 = up to 50cc.
Class 2 = 50-250cc
Class 3A/B = Unlimited or whatever else if they want to change the classifications (letter for clarification on the transmission)
For the tax thing…that’s not quite true. That’s what I thought at first too, but further up in the thread @cdn1234 helped clarify and there’s an overlap between orange plate and red plates on taxes. In the end I just guessed it was a classification for the purposes of opening up the freeways and expressways.
While technically the govt. is supposed to let red plates on the National Highways as the regulation change has already passed all 3 readings many years ago, as you say in practice you aren’t allowed and the highway police will go after you real quick.
But there’s an exception, the 3A highway has been open for over a decade for heavy motorcycles…so I’m assuming this includes orange plates too.
It’s even weird with provincial highways which should be fine for white plates too…but here’s one example that bans white plates down South on the #9…the speed limit is 70 like a lot of other provincial highways but apparently on a straight smooth road it’s way more dangerous than winding through the hills 
Must be some magic that makes riding 70 in Shuili going in a straight line okay, but over here driving it’s dangerous. Must be the ghosts. Makes more sense if they want to ban green plates…but banning white plates that can easily go the speed limit and are allowed to go that speed in many other prov. highways…it’s just silly.
I think they could also just change the regulations to say that white plates (maybe require ~125cc) can go on the expressway without passengers. I’m basing that off of the #74 freeway in Taichung…which has a max speed limit of only 80…
Then there’s the Suhua section, opened up for Heavy Motorcycles a few years ago and now this year finally going to open up on a trial basis for white plates…I thought the whole point of the new tunnel was safety so being forced to take the old road around seemed counterintuitive…
From wiki: Suhua Highway Improvement Project
