• Nov 2, 2020 CR Schedule Changes

  • 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 Diverging Route
 
Announced yesterday:

From Railpace

The Foxboro pilot will also be suspended for six months.
  by NRGeep
 
DMU's could be optimal off peak when distancing is possible and post pandemic during rush hour on some routes with many folks continuing to work from home permanently with cubicle office structures likely history.
  by rethcir
 
We aren't getting DMUs within the next year unless I missed something.
  by johnpbarlow
 
Given the T's current 10% of pre-pandemic level of ridership, some commuter rail train consists could be reduced to a double deck cab car plus locomotive - a DMU proxy! :wink:
  by nomis
 
Given the inadequacies of the signal system on the system, you need those 4 car consists (5 cars on the dorchester branch) to operate at track speed.

Splitting consists with the goal of increasing operating sets would only be limited by the available quantity of: locomotives, cab cars, and toilet cars.
  by johnpbarlow
 
nomis wrote: Thu Sep 17, 2020 6:04 am Given the inadequacies of the signal system on the system, you need those 4 car consists (5 cars on the dorchester branch) to operate at track speed.

Splitting consists with the goal of increasing operating sets would only be limited by the available quantity of: locomotives, cab cars, and toilet cars.
I guess things have changed since the RDC days wrt sigals?
And I wasn't advocating increasing train frequencies with the proxy DMU suggestion - perhaps some pruning of the frequencies should be implemented.
  by west point
 
Signal problems due to wheel profile changes. Not enough contact so more aels needed as Amtrak and missouri mules.
  by Trinnau
 
It's a combination of increased regulation and increased focus on safety. Train stopping calculations are made based on the number of brakes on a train and how heavy the train is. MBTA's stopping distances are based on a 4-caoch train. Even though a shorter train is lighter, it doesn't have as many brakes to help stop it. So in other words, a 3-car train actually takes more distance to stop than a 4-car train.

Based on this factor, the MBTA signal system is spaced such that a 4-car train can stop safely from the maximum speed on the line. A 3-car train would not be able to reliably stop in time and could overrun the signal.
  by johnpbarlow
 
Thanks for the detailed explanation, Trinnau. Very interesting and helpful. I'm guessing that any future DMU technology used by the MBTA would also require ~ 4 car set to operate? Or at least enough axles to stop the lighter-than-locomotive-hauled DMU consist safely.
  by MBTA3247
 
I don't think the above calculations would apply to DMUs, as the braking power/ton ratio remains the same regardless of how many cars you have.
  by Trinnau
 
Any DMU/EMU would need to be recalculated based on the brake rate they have and how that falls within the existing signal system. Keep in mind the current 4-car set includes the braking power of a locomotive in addition to the coaches. Now the ability to reliably shunt the signal system on the other hand may be an issue. Most railroads have a minimum axle requirement in the 12-16 range to not require additional protection. I think the MBTA's is either 16 or 20.

Back to the topic of schedules*, based on the T's recent history they are usually available about 3 weeks prior to the change date. So I'd expect details mid-October.

*Emphasis added by moderator