Record prices for gasoline and jet fuel should be good news for Amtrack, as travelers look for alternatives to cut the cost of driving and flying. Amtrak set records in May, both for the number of passengers it carried and for ticket revenues — all the more remarkable because May is not usually a strong travel month. Many of the long-distance trains are already sold out for some days this summer. Want to take Amtrak's daily Crescent train from New York to New Orleans? It is sold out on July 5, 6, 7 and 8. Seattle to Vancouver, British Columbia, on July 5? The train is sold out, but Amtrak will sell you a bus ticket. “We're starting to bump up against our own capacity constraints,” said R. Clifford Black, a spokesman for Amtrak. The number of “passenger miles” traveled on intercity rail has dropped by about two-thirds since 1960, and the companies that build rail cars and locomotives have also shrunk, making it hard to expand. In 1970, the year that Congress voted to create Amtrak by consolidating the passenger operations of freight railroads, the airlines were about 17 times larger than the railroads, measured by passenger miles traveled; now they are more than 100 times larger. Highway travel was then about 330 times larger; now it is more than 900 times larger. Today Amtrak has 632 usable rail cars, and dozens more are worn out or damaged but could be reconditioned and put into service at a cost of several hundred thousand dollars each. And it needs to buy new rail cars soon. Its Amfleet cars, the ones recognizable to riders as the old Metroliners, are more than 30 years old. And the Acela trains, which have been operating about eight years, have about a million miles on them. Scarcity is not all bad for the railroad, though. It has raised ticket prices, so that it recorded ticket revenues of $153.4 million in May, up 15.6 percent from $132.7 million in May 2006. That jump is higher than the ridership increase of 12.3 percent, to 2.58 million, from 2.30 million. Profits are unlikely. The Government Accountability Office found last November that Amtrak had received more than $30 billion in federal aid since its creation in 1971, but was still in “poor financial condition,” with extensive deferred maintenance. When Amtrak began operating 37 years ago, the plan was for it to eventually break even. In 1997, Congress passed a law threatening dire consequences if it did not reach self-sufficiency by 2002. By 2002 the mood had changed, and the appropriations have continued, financing losses of over $1 billion a year.