Straight Track #114

NTSB Blames Coal Train Derailment On Dynamic Brakes, Excessive Speed

U.S. Rail News
Vol. 25 No. 11
Published May 22, 2002

U.S. Rail News, in Vol. 25 No. 11, recounted a recent NTSB report on the government agency’s recommendations for calculating speed limits on steep grades. 

Railroads should avoid relying too heavily on dynamic braking to slow trains on steep grades, the National Transportation Safety Board (NTSB) warns in a new report. Instead, railroads should calculate speed limits on steep grades based upon the ability of air brakes alone to stop trains. 

The recommendation comes from an NTSB report on the Jan. 30, 2000, derailment of a CSX Transportation coal train at Bloomington, Md., that killed a 15-year-old boy and seriously injured his mother when the train hit their house. Track and equipment damage was estimated at $3.2 million when 76 of the train’s 80 “bathtub” high-side gondola cars derailed on a curve. 

The NTSB “determines that the probable cause…was the railroad’s practice of including dynamic braking in determining maximum authorized speed without providing the engineer with real-time information on the status of the dynamic braking system,” the federal investigative agency said. 

Dynamic braking refers to a method in which a locomotive’s traction motors are converted to electric generators driven by kinetic energy from the moving train. The generated electricity flows into a resistor grid and is dissipated as heat. The electrical load on the tractor motor slows the shaft rotation, thus braking the main wheels. The dynamic braking system on locomotives is independent of the air braking system on rail cars. 

In the Bloomington derailment, dynamic braking failed to adequately slow the CSX coal train as it descended “17-mile grade.” The engineer activated the emergency air brakes but the heavy train continued accelerating, eventually derailing at 59 mph along a stretch of track with a speed limit of 25 mph. Among its conclusions, the NTSB said: 

• “By using the effects of dynamic braking in its speed calculations, CSX Transportation established a maximum authorized speed over and down 17-mile grade that was too high to ensure that heavily loaded trains could be stopped using air brakes alone.” 

• “No matter what actions the engineer took, he probably could not have prevented a runaway because of the speed at which he was authorized to operate and the condition of the dynamic brakes.” 

A copy of this 42-page GAO document, titled “Derailment of CSX Transportation Coal Train V986-26”, is available through U.S. Rail News’ DocuDial Service as Document No. 51-4575. For more information or to place an order, call U.S. Rail News at 800-274-6737. 

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