(FORTUNE Magazine) – Sleek, lightning-quick bullet trains are a common sight in Japan and Europe, so why aren't there any in the U.S.? The short answer is that most American < railroad track wasn't built for ultra-high-speed travel. The Amtrak route from New York to Boston, for example, is so filled with twists and turns that over the 231-mile trip a passenger goes around the equivalent of 12 complete circles. If a bullet train hit 150 mph on some sections of this track, it could shoot right into Long Island Sound. Straightening the route would require buying lots of costly land and rights of way. So what's the answer? Early next year Amtrak plans to test a high-tech solution in the form of a new train design developed by ABB Asea Brown Boveri, the Swiss-Swedish electrical equipment giant. Called the X2000, the $13- million-plus train takes curves at high speeds because each of the train's axles can pivot independently. In conventional trains, the axles are fixed in steel frames called trucks. The trucks pivot as the train goes into a curve, but the fixed axles stay parallel to each other, even though the front axle wants to go in a different direction from the rear axle (see diagram). As any high school physics student can tell you, this is a ''conflict of forces.'' Normally, the conflict just causes wear and tear on the track, but if the train is going too fast, the wheels jump the rails. On the X2000, however, the axles are connected to the trucks by layered sandwiches of steel and rubber that act like springs. These springs are rigid enough to keep the axle steady while the train is going down a straightaway but flexible enough to allow the axle to pivot when the train heads into a curve. Since the train's wheels are thus aligned with the track at all times, the X2000 can safely maintain constant speeds of up to 150 mph. (Amtrak Metroliners hit 125 mph at their fastest. France's TGVs, the world's speediest, reach 186 mph.) To counterbalance the strong centrifugal forces in a curve, the train also has a computerized hydraulic system that tilts each car as it rounds a turn. On-board sensors calculate the train's speed and the sharpness of the curve and feed this information to hydraulic pumps under the floor of each car. The pumps tilt the car as much as eight degrees, causing it to lean into the curve like a race car on a banked track. That way neither passengers nor luggage go flying. The X2000 is already in service on the 284-mile line between Stockholm and Goteborg, Sweden's two largest cities. It cut the trip from four hours to under three, and increased ridership 20%. ABB will bring the X2000 to the U.S. later this year, and Amtrak will put the trains into limited service next spring. On the New York-Boston line, the X2000 is expected to reduce travel time from 4 1/2 hours to less than three. Riders won't see the full improvement until 1996, when the track east of New Haven is scheduled for electrification. Until then, the X2000 will be pulled by turbine power cars on that stretch. On the fully electrified, relatively straight New York-Washington line, the X2000 should immediately lop another 20 minutes off the present two-hour, 35- minute trip. Other possible routes: Chicago-St. Louis, Chicago to Milwaukee and the Twin Cities, and Miami-Orlando-Tampa.