Like its model, the Eurailpass, the USA Rail Pass allows you to make unlimited trips within a particular time period for a single lump sum. And because the discount it offers is so advantageous to frequent rail passengers, its sale has been restricted -- until now -- to persons residing abroad.

For reasons they haven't yet explained (and why look a gift horse in the mouth), the officials of Amtrak have just announced that U.S. residents will now be permitted to buy and use the USA Rail Pass. Details for purchase are at tel. 800/872-7245 or at http://tickets.amtrak.com/itd/amtrak/selectpass.

The pass is for three different periods of use: 15, 30, and 45 days of travel. The 15-day pass offers eight different trips for $389 ($48.63 per trip). The 30-day pass offers 12 segments of travel for $579 ($48.25 per trip). The 45-day pass offers 18 segments of travel for $749 ($41.61 per trip). Let's assume you want to make six round-trips between New York and Washington, D.C., in a one-month period. Buying the USA Rail Pass cuts the cost of each one-way trip to $48.25.

The pass is not available for the Acela or Florida-bound Auto Train. But it brings about a remarkable saving for frequent travelers making use of other trains. This is significant news, and an example of the kind of transport values that an expanded and improved, high-speed Amtrak could bring to our lives.