I find it rather bizarre that both sides are discussing this issue strictly in the hypothetical. There are already at least a couple of existing “experiments” in expanding passenger rail service in operation.
*California, the state with a long reputation of being completely car-crazy, has built up a good intercity rail system with state money (Amtrak operates the trains as the state’s agent) and lured several thousands of people out of their cars. The Surfliner corridor between San Luis Obispo, Los Angeles, and San Diego has 11 trains a day in each direction. The Capitols corridor between San Jose, Oakland, and Sacramento has seven daily round-trips. And the Oakland/Sacramento to Bakersfield corridor, the San Joaquin, has five round trips daily. Each of these corridors has consistently-rising ridership, and the state plans to add trains to each over the next few years.
*Washington and Oregon finance (with Amtrak operation) the Cascades corridor between Vancouver, BC and Eugene, OR but mainly connecting Seattle to Portland. This is another multi-train corridor where 10 years ago one or maybe two trains a day operated. The ridership on this route has been constantly growing since day one, and additional trains are in the works for the Cascades corridor as well. The trains are state-of-the art and very comfortable.
*And of course the Northeast Corridor from Boston to south of Washington, with fast trains at least once an hour from early in the morning to late at night. Of course, it was always a traffic-heavy line and was never allowed to decline after the private companies left the rail passenger business. Nevertheless, its achievements during Amtrak are still impressive, and the NEC carries 70% of all non-auto traffic between New York City and Washington DC. Yes, more people take the train than fly along the Northeast Corridor.
All of these trains operate right now in this country, not ten years from now or across the sea in Japan or France. And contrary to the fears of the randites on this board, none of them derive their growing ridership from government coercion. Nobody was compelled by threat of law or pointing of gun to get on these trains. 
And their ridership did not depend on some “Soylent Green” future where the fuel is depleted. No, the existing congestion of our national highway system was more than sufficient incentive for people to voluntarily use the trains.
They all use the “19th Century technology” of steel wheels on steel rails. Well, guess what, the electric light, the safety elevator, the telephone, and radio are all “19th Century technology” that we rely utterly on in this 21st Century. Come to think of it, that utterly-modern automobile that is supposedly the by-all and end-all of transportation was also invented, as the “horseless carriage,” in the latter years of the 19th Century.
These corridors prove that where you offer multiple round-trips a day between major population centers 500 miles or fewer apart, the ridership IS there. And contrary to Senator McCain’s assertion that rail can only work in the Northeast and California, there are several places in the country where major cities are 500 or fewer miles apart.
In the Midwest, the state governments of Illinois, Michigan, Wisconsin, Indiana, Ohio, and Minnesota are working on a plan for a Midwestern high-speed network. With federal monetary assistance but still a considerable state expenditure, improvement to existing freight trackage has been underway for some years. These improvements include the improvement or elimination of grade crossings, so autos and trucks directly benefit as well. And these states, through Amtrak as their agent, have already requested bids for trainsets able to travel at 110mph. Such train sets are already mass-produced for the rail systems of other nations, so we aren’t talking Buck Rogers stuff here. This system is on track 
to be operating in 2003 Chicago to Saint Louis, Chicago to Detroit, and Chicago to Milwaukee and Madison. Later extensions will be from Chicago to the Twin Cities, to Cleveland, and to Indianapolis and Cincinnati, and from Cleveland to Cincinnati by way of Columbus.
Nobody is seriously suggesting that the automobile or airplane be REPLACED by rail travel. Though I commute to work in downtown Chicago by train, I also own and use an automobile. When I travel from Chicago to New York, I fly because it’s faster. But would flying be faster, downtown-to-downtown, from Chicago to Saint Louis, or Chicago to Detroit, if trains could traverse those distances at just 100mph?! The ever-increasing ridership of the existing passenger rail corridors proves that where large population centers lie 500 miles or fewer apart, the government could move more people for fewer tax dollars by improving the EXISTING rail lines and buying high-speed train sets than by building extra road lanes which fill up with cars as soon as they are completed, and thus solve nothing, or new airports which gobble up hundreds of expensive acres of suburban housing and farmland. It’s not an issue of government versus private spending, it’s a cheaper government program versus a more expensive one.
