One of the ancillary benefits which is often inappropriately highlighted as a primary benefit by high speed rail proponents is that of reducing American oil consumption. Often, our reliance upon foreign oil, including some from Middle East nations such as Saudi Arabia, is seized upon by such proponents and the defense costs added to the price of oil. This, however, is a flawed notion that ignores the interconnected nature of global trade. Even if we were completely independent from foreign oil, or at least oil not from North America and Europe, including our shipping, we would still fund foreign militaries and place troops in these areas. A sudden lack of oil shipments from Saudi Arabia would cause major oil price shocks globally, not merely to those depending on oil from Saudi Arabia. Even if we were, by perhaps some magical free energy device, completely free from oil use except in raw industrial processes, we would still be gravely damaged economically because our economy depends on foreign trade. Major economic recessions or depressions in our trading partners will cause the same problems here as well.
Now, for the actual matter at hand, that of high speed rail's role in reducing our dependence on oil. The California High Speed Rail Authority estimates that, by 2030, the high speed rail system will be saving 12.7 million barrels of oil per year. This, however, represents only sixteen hours worth of US consumption in 2009 and only 1.9% of California's annual consumption (one week's worth). Clearly it would have minimal, if any, effect on oil prices or oil dependence.
Ultimately, the problem of oil consumption is going to be best handled through regulations and industrial subsidies (such as paying Ford to bring over the 65mpg Fiesta ECOnetic) which increase the average fleet fuel efficiency from its currently pitiful 22.6 miles per gallon to a rather higher figure. Saving fuel via HSR is helpful, but it is nothing more than a bandaid compared to what really must be done and it is a far from economical means of so doing.