On my ride up to Albany yesterday, we passed a couple of Metro-North Poughkeepsie trains being pushed by dual-mode diesel/electric power south towards Grand Central Terminal. We were south of Croton-Harmon in both cases, and what was interesting was that as we passed the train, it was obvious that the locomotives were running on their diesel engines. Now I know that the locomotives run on third rail power into Grand Central Terminal, but the third rail runs all the way to Croton-Harmon, and I was surprised that they weren't using it. I would have thought at the very least that the MPO for the New York Metro area might want to encourage all-electric running when possible in order to scarf up some emissions credits under the Clean Air Act for the region. Is there some reason that Metro-North would want to run their diesel engines on their dual-modes when electric is available? It can't be like MARC running diesels on the Penn :Line because Amtrac charges them too much for electricity, presumably, this is Metro-North electricity anyway.