Line of sight not enough to prevent June 22 crash
A National Transportation Safety Board (NTSB) sight-distance test shows that the train operator in the June 22 crash probably wouldn’t have realistically seen the stopped train soon enough to prevent a collision when the signaling system failed.
The operator appears to have applied the brakes less than three seconds after first “full sighting” when it was clearly visible, but that was still not early enough to prevent the collision.
This demonstrates that a working signaling system is absolutely vital to Metrorail safety. If the signal system fails, then manual operation does not necessarily protect trains from colliding.
While the final NTSB report on the collision is not likely to be published for several more months, the NTSB released documents and exhibits about the incident in preparation for this week’s hearing.
According to the report, Train 112 was probably traveling at about 52 mph when the brakes were first applied.
Based on a report on track geometry, ambient conditions, and the braking capabilities of Train 112, it would have been possible for the train to stop prior to collision with Train 214 if the brakes had been applied at first partial sighting of the stopped train and also with a 3 second response time, even with a minimum brake application.
The first partial sighting of Train 214 was 1,121.5 feet. At this position and time of day, the stopped train is in shadow and is screened by the chain-link fence running alongside the Shady Grove-bound track. It is also obscured by the vegetation on the west bank of the railroad cut.
The report also shows braking based on first full sighting of the stopped train. This is 471 feet from the point of impact, a little more than the length of a 6-car train. Even an emergency brake application at this point would not have averted the collision, but would have slowed the train to about 24 mph. A three second-delay in response time would have resulted in a crash speed of 44 mph.
Based on the steel bluing (skid marks) on the rails, the operator of Train 112, Jeanice McMillan, probably applied the brakes less than three seconds after the point of first full view, but not in time to stop the collision from occurring at at least 33 mph.
The NTSB identified a “last point” to stop after which a collision was inevitable. That point is about 400’ after the first partial sighting, and about half the distance to the full sighting.
The collision happened around 15 seconds after the first partial sighting of the stopped train, or around 5 seconds after the first full sighting.
It is important to note that even when the stopped train came into view, it might not have been clear to the operator of Train 112 that the visible train was stopped on the Shady Grove track (Track 2). This was reported to be a factor when a Metro train struck wayside workers at Eisenhower Avenue in November 2006 (page 5).
These tests show the importance of the ATC system. Line-of-sight often does not present enough time or distance to stop trains, which is why railroads and transit systems use signal systems. It is absolutely vital that fixes for the ATP train detection system be found.
In past discussions, some commenters have wondered about color-light signals as a solution. It appears that in this case, they would not have made much difference. The track circuit where Train 214 was stopped failed to detect Train 214. If color-light signals had been present, they would have displayed a “clear” aspect in the same manner that the ATC system sent “clear” to the cab speed signals on Train 112.
If WMATA and its passengers cannot be confident in the train detection system, there can be no true confidence in passenger safety. That’s why it is so important to design and implement at least one backup system. San Francisco’s BART did so in the early 1970s, and WMATA tells us that they are working on a system now. WMATA hopes that such a system can be in place by the end of this calendar year. For riders, that system cannot come soon enough.