Amtrak says a 20" folder can be brought in the passenger cars to put in the luggage shelves at end of cars, but that's not the LIRR. Usually, I would think not a lot of luggage with passengers on that, unless the majority of folks going to and from an airport. Which means a lot of space fore/aft on the overhead luggage shelf. Now, if sticking over the side laterally, yeah I'm sure that would get called out. I'm also sure a G-Line could not be brought on board aircraft, I think a 22" roller can fit overhead, and the G is over that. But 16" Broms have been brought on board. I was nervous on a return train trip, in the tall scenic cars, seats on top level, because the luggage shelves were on the lower level near the door. At every stop I went down to keep an eye on my bike, lest someone grab and go in 2 seconds. In the future, I'll prefer the regular cars with the luggage shelves in sight.