• 1/17/2022 Park St Green Line Derailment

  • Discussion relating to commuter rail, light rail, and subway operations of the MBTA.
Discussion relating to commuter rail, light rail, and subway operations of the MBTA.

Moderators: CRail, sery2831

  by GaryGP40
 
It's *possible* that the operator of the D train also attempted to reset the signal to get clearance to the fence track (which makes sense if if it a Riverside trolley) and didn't realize the switch was already occupied. The signal should not have cleared to realign it while the track was occupied. So it could be a confluence of issues involved.

If the dispatcher had told the D operator that they needed to take the wall track, then it doesn't make sense the operator would have tried to reset the signal.

Is this just a T investigation, or is the NTSB also involved? My guess is this is just the T. Have to keep an eye out to see what happened. The investigation continues...
  by Disney Guy
 
If the operator saw the signal or the switch set for the wall track and s/he really wanted the fence (center) track (or vice versa), then s/he would leave the train stopped at the interlock signal and go out and push a reset button while the facing switch to be negotiated is still in front of the train.

Some interlocks, perhaps this one, are set up so that points of neighboring switches are moved as needed and if possible to avoid leaving a conflicting path. Here, that means that when the trailing switch (to the fence track) is set for a looping train, the facing switch entering Park St. westbound will be set to wall track which will divert any arriving westbound train that fails to stop and that threatens to hit the looping train. (Think: Divert it onto a parallel track.) If an arriving westbound put in a request for the fence track but the looping train got there first, the double red continues to show for the westbound train.

Whether desired or not, the train went onto the wall track. Still so far so good although too late to discuss resetting the signal.. Even if the operator requested the fence track but did not wait for it, the system must not change the switch automatically while the train is upon it. The operator must not back the train up without protecting the back of the train from a following train, said protection normally done by starter(s) on the ground perhaps wielding flags. At any rate the reset buttons are no longer within easy reach without walking back. For Park St. westbound, the operator ending up on the wrong track could just proceed to the platform. Both (the fence and wall) tracks converge at the station exit to continue to Boylston St.
Last edited by Disney Guy on Mon Jan 24, 2022 10:09 am, edited 4 times in total.
  by theMainer
 
GaryGP40 wrote: Sun Jan 23, 2022 9:19 am It's *possible* that the operator of the D train also attempted to reset the signal to get clearance to the fence track (which makes sense if if it a Riverside trolley) and didn't realize the switch was already occupied. The signal should not have cleared to realign it while the track was occupied. So it could be a confluence of issues involved.

If the dispatcher had told the D operator that they needed to take the wall track, then it doesn't make sense the operator would have tried to reset the signal.

Is this just a T investigation, or is the NTSB also involved? My guess is this is just the T. Have to keep an eye out to see what happened. The investigation continues...
I remember last month while I was on an (E) Heath Street trolley that the operator had to stop and get out to set that switch. So an issue with the switch could be a potential possibility.