The Associated Press

CRESCENT CITY - Federal investigators say the Thursday April 18 derailment of an Amtrak Auto Train that killed four and injured more than 150 may have been caused by expansion of the tracks.

Russ Quimby, an investigator with the National Transportatioin Safety Board, told the Orlando Sentinel in a story published in Friday editions, that the rail at the accident site had not been adjusted so it could expand in hot weather.

But Gary Sease, a CSX spokesman in Jacksonville, said Friday that CSX, which owns the rails, performed the procedure, known as adjusting the "neutral rail temperature," on Wednesday Feb. 27 and Tuesday March 12.

In a statement released Friday, the NSTB said it was continuing to gather information on the tracks.

"The investigation is focusing not only on the physical condition of the track structure at the time of the accident, but track maintenance policies and procedures, maintenance reporting processes, and management oversight by CSX and the FRA (Federal Railroad Administration)."

The neutral rail temperature procedure re-stresses the steel so that it will not expand too much and buckle when exposed to high temperatures. In the South, the track is heated to 100 degrees, while a 90-degree temperature is used in the North.

The engineer of the Amtrak train reported seeing a buckle, or "sun kink," just before his train hurtled off the track in Putnam County.

Buckles are a well-known risk associated with the type of track used south of Crescent City. Called continous welded rail, it has no joints. Instead, strips of rail are welded together, forming ribbons of steel that can stretch for thousands of feet. Welded rail is cheaper to maintain, reduces wear and tear on rail cars and provides a smoother ride.

But as welded rail expands in the heat, there are no joints to relieve the pressure on the steel. The day after the Thursday April 18 derailment, investigators measured the track temperature at 120 degrees, though the air temperature was only 88.

Eventually, the pressure becomes too much, and rail buckles, sometimes bowing out by more than a foot. When a train runs over such a buckle, it can cause a derailment, the newspaper reported.

CSX also performed other routine track maintenance in the area in October, November, February, and March, replacing ballast and aligning tracks, Sease said,

The NSTB also is continuing tests of the Auto Train's braking system at a facility in Fort Worth Texas.

"Investigators are looking at the effect the different braking systems may have had on Auto Train since the train unique combination of passenger and automobile-carrying railroad cars,"the NSTB said.

The federal agency also is looking at two metal couplers which linked the Amtrak Superliner cars together. Several couplers, which are designed to keep cars upright and in line in a derailment, broke during the accident.

In the past two years, the Federal Railroad Administration has become convinced that CSX has significantly improved its track and track-safety procedures and agreed to end years of special supervision it had put CSX under in 2000. The decision came two days before the Amtrak crash.

Sease said CSX has improved its safety record. In 201, there was a 30 percent improvement in train accidents over 2000 and another 25 percent reduction in the first two months of 2001.

NSTB is expected to wrap up its fact-finding for the Crescent City crash this summer. A final report may be released in September.