On January 7, 2007, about 3:45 p.m. eastern standard time, northbound Washington Metropolitan Area Transit Authority Metrorail train 504 derailed one car as the train traversed a crossover from track 2 to track 1. The accident occurred in an underground tunnel on the Metrorail Green Line near the Mt. Vernon Square 7th Street-Convention Center (Mt. Vernon Square) station at chain marker E2 23+28. The train was traveling about 18 mph as it approached the station.
The train consisted of six cars. The fifth car from the head end of the train derailed. About 80 passengers were on board at the time of the accident. Twentythree passengers were transported to local hospitals for treatment and released. Emergency response personnel from Washington, D.C., provided the on-scene treatment and transportation of the injured passengers.
The National Transportation Safety Board determines that the probable cause of the January 7, 2007, derailment of Washington Metropolitan Area Transit Authority train 504 as it traversed a standard turnout track near the Mt. Vernon Square station in Washington, D.C., was a wheel climb on car 5152 that was initiated by a rough wheel surface created when the wheel was trued with a milling machine, the lack of quality control measures to ensure that wheel surfaces were smoothed after truing, the lack of a guard rail on the No. 8 turnout, and Washington Metropolitan Area Transit Authority's failure to have an effective process to implement safety improvements identified following similar accidents and related research projects.
As a result of its investigation of this accident, the Safety Board identified the following safety issues:
- Wheel-truing procedures
- Mitigating measures for wheel climb derailments
- WMATA interdepartmental coordination
As a result of its investigation of this accident, the National Transportation Safety Board makes recommendations to the Washington Metropolitan Area Transit Authority.
As a result of its investigation of the January 7, 2007, derailment of Washington Metropolitan Area Transit Authority Metrorail train 504 near the Mt. Vernon Square station in Washington, D.C., the National Transportation Safety Board makes the following safety recommendations:
To the Washington Metropolitan Area Transit Authority:
Develop a standard for maximum allowable wheel roughness and develop and implement post-wheel-truing procedures to meet that standard. (R-07-23)
Implement quality assurance procedures to ensure accurate wheel truing, including the regular alignment and indexing of cutting heads on wheel milling machines. (R-07-24)
Establish procedures to ensure that there is appropriate coordination between all departments responsible for car maintenance and engineering design to ensure that problematic issues are identified, examined, and resolved before new equipment is ordered. (R-07-25)
Establish a process, including a single point of responsibility, to prompt timely evaluation and action on proposed safety improvements that are identified as a result of accident and derailment investigations and related research projects. (R-07-26)
Establish written procedures for rail lubrication that include close coordination between the operating and track engineering departments to ensure timely and appropriate rail lubrication is applied in normal and single-track operations. (R-07-27)
Expedite and complete by 2009 the replacement of all No. 8 standard turnouts with guarded turnouts on main track. (R-07-28)