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| Re: Uh oh.. Northbound A Train Was Travelling on Southbound Tracks--- There Was No Fog on the Tracks (1309778) | |||
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Re: Uh oh.. Northbound A Train Was Travelling on Southbound Tracks--- There Was No Fog on the Tracks |
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Posted by Stephen Bauman on Wed Aug 27 19:39:39 2014, in response to Re: Uh oh.. Northbound A Train Was Travelling on Southbound Tracks--- There Was No Fog on the Tracks, posted by Train Dude on Wed Aug 27 16:45:53 2014. The reason were a combination of the 15% increase in horsepower and the fact that the signal system was never adjusted to compensate for it.One factor you did not consider was the emergency brakes were below spec. N.B. they could have increased the emergency braking rate to compensate for increased maximum attainable speed (MAS) due to increased horsepower. In fact, the BOT reduced emergency braking rates with the introduction of the R10. The R1/9's spec matched the BMT's - emergency stopping distance 250 ft from MAS. The R10 spec was 275 ft. N.B. signal design adds a 35% fudge factor. The distance from the tripper on the WB to the point of impact was 288 ft. The follower's estimated speed at that tripper was 36 mph or 60 ft/sec. Stopping within 288 ft would have required an emergency braking rate of 4.25 mph/sec. The NTSB ran 3 tests on the bridge. On the first test the train hit the tripper at 34 mph and took 364.5 ft to stop. That's an emergency braking rate of 2.3 mph/sec. On the second test, the train again hit the tripper at 34 mph and took 358.5 ft to stop. That's an emergency braking rate of 2.4 mph/sec. The NTSB ran a third test as a control. Full service braking, rather than emergency braking was applied. The train hit the tripper mark at 33 mph and stopped in 162.2 ft. That's a braking rate of 4,9 mph/sec. It also stopped the train 125 feet short of collision. |
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