The last time I rode the MVT, I shared the trail with a CaBi rider – he did the whole round trip, and while he kept to his pace he probably never went over 15 mph. (That’s a silly way to spend money IMHO, but that’s his business.)
Without signage, how would we or USPP or anyone expect him to know that riding on the GWP roadway is in fact not permitted? He’s not “a cyclist”, he was just out riding a bike, and if he saw others on the roadway he could be somewhat excused for thinking that’s where people riding bikes are supposed to be.
Used to be only high-speed cyclists would do this, used to be the USPP would look the other wawy, but in the last few years I’ve seen more and more average riders on the GWP roadway, at more and more risk of having a tragic collision.
I doubt these new signs mark a huge change in enforcement practice, but they should keep some of the more casual riders from getting onto a road that’s above their abilities.
(By the way, much of the Baltimore-Washington Parkway has wide shoulders that are much more paceline friendly. Still illegal, but that’s not really the question at hand…)