We all are aware that trains are among the most sustainable present-day motorized transportation these days. Amtrak has its own page about how it commits to sustainability: http://blog.amtrak.com/2014/01/amtrak-commits-sustainability/

It has received a sustainability score of 85, which is a B. Yes, the sustainability score has a very similar scale as academic grading. As a matter of fact, it remains one of the more environmentally friendly form of transportation, where only 2,435 BTUs are used, compared with 2,826 BTUs per airliner and 3,538 BTUs per car.

Here is a link to the 2012 sustainability report:  http://www.amtrak.com/ccurl/883/945/Amtrak%202012%20Environment%20and%20Sustainability%20Summary_Final.pdf