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 dynamic brakes, automatic airbrakes, locomotive independent brakes, and continuous cab signals that had speed control, event recorders or speed tapes, and radios.

Tunnel, Signal, and Track Information
—At the west end of the Back Bay station platform, the tunnel is approximately 86 feet wide. The derailment occurred at MP 227.45, where the tunnel is approximately 62 feet wide in a 9&deg; 30' curve. The three main tracks (1, 2, and 3) run south to north Between tracks 1 and 3, a 3-foot thick, 8 1/2-foot high concrete crash wall with support columns restricted the width of the tunnel for tracks 1 and 2 to approximately 36 feet. The passenger loading platforms are between tracks 1 and 3 and on the south side of track 2.

—The automatic block and control signal indications from the CETC system in the Boston train dispatcher's office govern train movements through Back Bay station. Control for train movement on main tracks is by signal indication, which operates trains in both directions using wayside automatic block and locomotive cab signals.

The automatic speed control system, which functions in signalized territory, is connected to the locomotive cab signal, it is independent of and not connected to the locomotive's speedometer and event recorder. If the locomotive engineer fails to reduce speed to the authorized level in cab signal territory, the speed control automatically triggers a brake application to slow and stop the train Signal 226 2 at Ruggles Street was not coded to provide the 30-mph speed restriction at MP 227.

Before the accident, the train dispatcher had routed Amtrak train 66 on track 2 for "clear, proceed" signals. The locomotive crew on Amtrak train 66 stated that both the locomotive cab signal and the wayside automatic block signal at MP 226.2 displayed "clear, proceed" aspects, indicating a clear track ahead and authorizing Amtrak train 66 to proceed at the maximum track speed of 100 mph. The train was authorized to operate at that speed until MP 227, where the speed restriction is 30 mph and remains in effect until MP 228.3. At the approach to the 30-mph speed restriction at MP 227, no speed signs were posted to warn of the restricted speed ahead.

—Built in 1987, the track is 132-pound continuous welded rail with 24-inch centered concrete crossties. It is ballasted to the concrete tunnel floor with 24-inch deep crushed rock Near the POD, the north rail is fitted with an operative wheel-flange lubricator about 750 feet west of the curve.

The MBTA owns the track, and Amtrak maintains it for trains operating at speeds up to 100 mph. Amtrak performs scheduled track inspections twice weekly, at intervals of at least 1 day, and does daily walking inspections of concrete ties. In May 1990, the Federal Railroad Administration (FRA) had inspected the track and noted no defects in the derailment area. An ultrasonic internal rail defect inspection of track 2 on October 20, 1990, also revealed no defects in the derailment area. On December 11, 1990, Amtrak conducted the last track inspection before the accident and found no defects in the derailment area.

—The POD was at MP 227.45 on track 2 Derailment marks on track 2 were approximately 2,262 feet past MP 227 inside the