National Transportation Safety Board
Office of Public Affairs
The National Transportation Safety Board today released the following information on its investigation of the June 28, 2004 collision of UP and BNSF trains and subsequent chlorine release at Macdona, Texas near San Antonio.
The Safety Board's investigation of the Macdona collision is on going. The on-scene portion of the investigation was completed on July 10; however, fact gathering and follow-up activities continue.
Sight Distance Testing
Sight distance testing was conducted near the collision point on July 1. To do sight distance testing investigators use a locomotive with a cab configuration similar to the accident locomotive. The testing is done at the same approximate time of day as the accident in an attempt to duplicate conditions. During the testing the locomotive is moved slowly up and back on the track to allow investigators in the locomotive cab to document how clearly and at what distance the train crew would have been able to see wayside signals as well as other traffic.
Event Data Recorders
All 6 event data recorders (4 from the UP train and 2 from the BNSF train) have been downloaded.
The recorder data indicate that the last control input on the UP train occurred about 30 seconds prior to the collision. Preliminary data from the UP recorders show no indication of control inputs to affect braking until the time of the collision. The UP train was traveling at approximately 45 mph and the BNSF train was traveling at approximately 20 mph at the time of impact.
Tank Car/ Hazmat Issues
Efforts to offload the remaining chlorine from the breached tank car have been completed. Investigators will conduct a detailed examination of the tank car.
Investigators continue to gather information about the emergency response efforts after the collision. An examination of first response efforts is a standard part of any NTSB investigation.
A preliminary review of signal system data did not identify any discrepancies in the system.
NTSB Office of Public Affairs: (202) 314-6100
The National Transportation Safety Board (NTSB) is an independent federal agency charged with determining the probable cause
of transportation accidents, promoting transportation safety, and assisting victims of transportation accidents and their families.