Moscow, Russia, has a very large population of homeless canines. A small minority of them hang out in its metro and have attracted international attention for using the trains to commute to areas they want to get to. A few theories are bouncing around about how they learned how to tell the difference between the trains to get where they want to go.
One theory is that they have an ability to judge the length of time spent on the trains and the time periods at which certain trains arrive. Another is that they recognize the place names when they are announced over the train’s loudspeaker.
Others think it could be the scents of the different stations, but it’s likely that it’s a combination of all three. Of course, it could be different for each dog.