From Lisa Schweitzer: Sustainable Cities and Transport blog HSR's energy/emissions promise and peril
Reviewing a recent study (Horvath and Chester (2010) "Life-cycle assessment of high-speed rail: the case of California" Environmental Research Letters 5 014003
doi: 10.1088/1748-9326/5/1/014003), Dr. Schweitzer notes of HSR:
Being the cleanest mode per passenger hinges on getting a critical mass of people using it. The timeframe for payback on emissions invested in the colossal investment: about 70 years. I won't see it, but my students might.
Ok, so this is better than Charles Lave found for BART (Lave, Charles. 1976. The Negative Energy Impact of Modern Rail-Transit Systems Science, February 11, 1977. Vol. 195, pp. 595-596.) , which required even more construction underground, but it is not a good payback period by any means. And this is assuming conventional modes as competition. Remember, you have to skate to where the puck will be, not where it was.