It is a wonkish post of the kind I was one day planning to write, and now don't have to, because Coyote Blog has pretty much retired the fantasy that urban commuter light rail systems would be better than hybrids or more efficient automobiles.
I particularly like his opening salvo:
I generally have a bet I make for new light (and heavy) commuter rail systems. I bet that for the amount the system cost to build, every single daily rider could have instead been given a Prius to drive for the same money; and, with the operating losses and/or subsidy the system requires each year, every one of those Prius drivers could be given enough gas to make their daily commute. And still have money left over. I have tested this bet for the systems in Los Angeles and Albuquerque.
Well, it turns out I left something out. Many people are interested in commuter rail because it is perceived to be greener, which nowadays generally means narrowly that it uses less energy and thus produces less CO2. But in fact, it may not. Blogger John Moore sent me a link to this article by Brad Templeton analyzing energy usage in various transportation modes. While a full train can be fairly efficient (just as a full SUV could be if 7 passengers were in it), cars and trains and busses are seldom full. When you look at their average load factors, trains are seldom better than cars:
The only refutation I can think of, regarding the analysis that follows this graphic, is a country in which the government so prohibitively taxed all urban automobiles that it would force greater ridership (I can hear my progressive friends salivating now). The problem with that, of course [aside from the obvious Statist implications] is that no matter how manner riders you have, your carrying capacity has to be figured based on your peak hours, which necessitates that your average will continue to be slightly less than half your peak ridership. Do the math.
So, no matter what, the energy cost ratios of light rail will always disappoint the unrealistic expectations of the advocates.
That won't, however, stop them from sticking their hands in your pocket and feeling about for (we hope) spare change.