by netrain
I am relatively new to the train world, so forgive my ignorance, but in the photo section, there is an image (http://railroad.net/photos/nycarea/media/ov-08.jpg) of two engines back-to-back pulling a metro north train on the harlem line towards wassaic. i always thought two engine were for really heavy loads, but this run is typically done by a single engine. can anybody enlighten me as to why there are two here?