Robert- my truck is about 22' and my FW is 42', but my overall length is only 58.5'. My with thought I was pretty crazy as we measured it with our little 10' tape measure!
So, in MD- trucks (even duallies) are NOT automatically registered as commercial. But, we do have special licensing requirements for trailers over 10,000 pounds or gross combined weights over 26,001.
That said- this prompted me to email the MD SHA email address that was provided in the handbook. I'm curious as to their take.
I'm also more curious as to what I'll do if it really is 55'!