All that being said: I don't think the federal government has the ability or the constitutional right to directly operate a passenger railroad service. In other words, I'm against AMTRAK. However, I am most definitely for the proposition that our federal, state, and local governments should cooperate to build and maintain the physical infrastructure of a linked network of regional high-speed rail transportation systems. In other words, I support the establishment of a national system of interstate and defense railroads -- the rail equivalent of the Eisenhower National System of Interstate and Defense Highways.
Just as the Interstate Highways are taxpayer-funded, the rail system I'm advocating would be built and maintained with public funds. Each state would operate its own regional rail network, just as they build and maintain their own sections of the Interstate highways. The difference is that on the national rail system there would be no traffic jams, no weather closures, and no billboards. There would also be no 55 mile-per-hour speed limit; trains would regularly operate at 150 to 190 miles per hour on the longer runs. These trains would be owned and operated by private, for-profit railroads; the government would no more run these trains than they run the trucking companies or motor coach (bus) operators today. The majority of funds for upkeep and improvement of the infrastructure would come from taxes levied on the carriers, just as trucking companies and bus lines pay for much of the highway system's operating costs today.
And finally travelers would have a choice! Instead of gulping down greaseburgers or attempting to digest the latest offering from Stuckey's or Perkins, travelers on these improved railroads could enjoy fine meals, served in a clean, comfortable dining car on real china with cloth napkins by a uniformed steward -- or they could eat home-cooked or other picnic foods in the Club Car. Unlike travelers in buses or private cars, rail travels could enjoy wine, beer, or liquor during their trips. Unlike airline travelers, their luggage would stay with them the entire time, they could "move about the cabin" to their hearts' content, there would always be an open restroom, and passengers who desired to could even -- gasp! -- enjoy a cigar or pipe in the Smoking Car or Lounge.
The trains would depart and arrive from convenent city-center terminals. That would sure beat sitting in traffic for an hour to get to the concrete bunker of the airport. And the pre-boarding rectal exam and underwear inspection would be a thing of the past.
Those who worry that the federal goverment has no right to build roads (or canals or airports) need not worry. Not only is such construction constitutional (Art. I, Sec. 8), but there is a substantial body of case law supporting its constitutionality (the Federal-Aid Highway Act of 1956, among many others). To argue otherwise is to argue against the existence of ports, airports, and the Panama Canal -- all of which required (and require) big honking heaps of taxpayer dollars to build and maintain.
I'm generally not a supporter of big government. In this case, however, I'm of the opinion that it is the duty of our governments to build and maintain a national high-speed rail system -- not to operate the service, but to create the infrastructure that will allow that service to exist.
A double-track rail line that can transport people at 70mph is IIRC about comparable in cost per mile to two lanes of interstate (it may be more or less depending upon grading conditions, etc.) Such a line can transport many more people than can a lane of interstate, if it's used to absolute maximum capacity. In practice, though, very few passenger rail lines are utilized to anything near the capacity of a lane of interstate.
Freight, btw, is a different matter. Many rail lines are used to haul far more coal or other bulk freight than could reasonably be transported by road. Even though most such lines are used to only a fraction of their theoretical maximum capacity, they provide a far more economical means of transport than anything else except waterways (with which they're about comparable).