My favorite 18xx game for six players is two games of 1846 with three players each.
If I have a 2 train, is it legal to commence a route at a large station, say Columbus, and run it directly to a yellow station hex A4, A5 or A6?
In other words the route begins at a large station but finishes in a small station.
Of course, a station marker would need to have been placed in Columbus.
Yes, running in that way is legal.
(Sorry for us old-timers asking you about the Mayfair tile numbers; we're just not used to them. Not really trying to pester you.)