Report - Sacremento Rail Crash - LR train position not known to controllers
According to the results of a preliminary investigation into an accident that occurred on Sacramanto's light rail system earlier this month, the control centre was not aware of the exact position of a passenger-carrying service train when a disabled train was given permission to pass a red signal.
The accident on 8 February 1999 occurred on a single track bridge when a train which had broken down was being assisted by another to reach a repair facility. This, and the service train met in a head-on collision causing minor injuries to 30 passengers.
A road accident had earlier blocked the track which had caused the train to get behind schedule. Thus it seems that the control centre believed that it had cleared the single track bridge when when the disabled train was authorised to pass the danger signal ('signal bypass'). Both trains were in communication with the control center, but using different channels. RT have suggested that if the trains had been using the same radio communication channel, then the operators of each of the trains might have known of each other's position.
The investigation has shown that there was no malfunction of any equipment. During the investigation tests were conducted which simulated the conditions in which the accident occurred.
RT have issued a statement concerning the results of the invstigation . . .
"That morning, after a light-rail train had malfunctioned near 39th Street, another commuter train was pushing it west toward the repair bay. RT maintenance personnel were on board, but no paying customers.
The train pushing the disabled car received permission from the control centre to proceed through a red light at the 23rd Street station -- a standard industry procedure called a signal bypass.
Meanwhile, the eastbound train carrying the passengers was making its way through the downtown area.
The disabled train was to have crossed the bridge between regular passenger train movements. The control centre thought the eastbound train had cleared the bridge when it gave the disabled train the signal bypass.
But that was not the case.
When the crippled train prepared to descend from the bridge, both trains suddenly came into each other's view. Travelling down a 7 percent grade on wet tracks, the disabled train was unable to stop in time to avoid impact.
The crash was not prompted by any malfunctions of the cars, track, signal system or overhead power system.
Speed also was not a factor. At first, it was thought that each train was travelling about 10 mph at the time of impact. But Robinson said that RT now estimates that the disabled train was travelling 18 mph -- slower than the 25 mph limit posted for that stretch of track -- and the other train had braked to a stop."