If you're interested in non-political discussion of air quality and transportation issues, look into Alan Kandel's blog, Air Quality Mattters [2], on the Science Blog [3] web site. His musings from last November on the effects of public transit development in mitigating air pollution [4] are particularly interesting. His most recent post, a brief discussion of the pros and cons of diesel-electric versus pure electric train operations [5], provides some background on the history of rail in the U.S. followed by discussion of motive power choices for now and the future.
Links:
[1] http://www.library.northwestern.edu/libraries-collections/evanston-campus/transportation-library
[2] http://alankandel.scienceblog.com/
[3] http://scienceblog.com/
[4] http://alankandel.scienceblog.com/2012/11/16/cutting-edge-transportation-effective-emissions-reductions-approaches/
[5] http://alankandel.scienceblog.com/2013/01/17/cats-diesel-electric-versus-pure-electric-train-operations-pros-and-cons/
[6] http://www.library.northwestern.edu/related-pages/pollution
[7] http://www.library.northwestern.edu/related-pages/transportation