Eastern Railroad Discussion > LSL v. DPU question

Attached is a grainy, blue hour iPhone photo of the mid-train DPU on CSX intermodal train L032 (I think) seen at Riverdale MD just north of Hyattsville on the ex-B&O main to Baltimore, etc. Note that the amber Locomotive Speed Limiter light below the cab window is illuminated presumably for L032's run over cab signal territory on the ex-RF&P on its journey from Jacksonville to N Bergen NJ. My question is how does LSL work for a mid-train DPU - wouldn't every block in cab signal territory present a stop aspect to a mid-train DPU locomotive? Does DPU override LSL? And lastly, will PTC make LSL use moot in cab signal territory? Thanks.



Edited 1 time(s). Last edit at 01/09/19 03:55 by JPB.

---

I am certainly not knowledgeable on this subject, but I would guess that the mid-train power responds in a similar way that the MUed multiple units do in the front of a train. Basically, the DPU is just another MUed unit in the consist but is simply a greater distance from the other engine partners. The lead engine has the control stands for the engineer to operate the train and the other units are simply responding in concert. 
Jim Leighty

jimleighty Wrote:
-------------------------------------------------------
> I am certainly not knowledgeable on this subject,
> but I would guess that the mid-train power
> responds in a similar way that the MUed multiple
> units do in the front of a train. Basically, the
> DPU is just another MUed unit in the consist but
> is simply a greater distance from the other engine
> partners. The lead engine has the control stands
> for the engineer to operate the train and the
> other units are simply responding in concert. 
> Jim Leighty

Yes, the remote engines are slaved to the head end. They do only what the engineer wants them to do. 

Based on what I've been told by several friends that are working on their carrier's PTC implementation, all existing legacy cab signal and train control systems must remain in place at least until full interoperability (when all carriers' PTC servers can network with each other) is achieved sometime in 2020 (we hope). After that, then each carrier can individually petition the FRA for discontinuance of each legacy system.

Example: On the UP's former C&NW east-west main across Illinois and Iowa, PTC is active yet the C&NW Automatic Train Control (ATC) must remain active and each train must still have an ATC-equipped leader, but IF the PTC initializes correctly at the intial terminal, then the ATC may be cut out and train may operate on PTC only. If there is ANY problem with the PTC en route, then the ATC must be cut in and tested before continuing under ATC. I would not be surprised if that is the same plan other carriers will be following as more cab signal/train control territory becomes overlaid with active PTC.

The above is only possible because UP has since the C&NW merger been steadily instaling wayside intermediate block signals in the former C&NW ATC territory. Prior to that, C&NW had no wayside block signals except at and approaching interlockings and control points. For other railroads without wayside intermediates in cab signal territory (e.g., NS ex-CR between Cleveland, Alliance and Pittsburgh)  this may also have to take place first, but I have no hard proof of that. 

Sidebar: The NS is trying to convince Amtrak to install the freight-industry-standard PTC (I-ETMS) on the portions of the NEC it operates over in order to avoid having to maintain a dedicated fleet of leaders equipped with Amtrak''s ACSES system. Again, that solution will not work until interoperability between the NS and Amtrak PTC "back room" server systems could be achieved.

FWIW,

NZ

A couple of points; LSL and cab signals would simply be cut out on DPU units. CNW's cab signals were, and are, not compatible with UP's; they are two aspect only, clear and restricting, UP's have four as do NS's. That's why intermediates are needed there.  Also, NS is eliminating intermediates where the ex-Conrail cab signals are in operation.  Their (and UP's)  cab signals will likely stay in operation even after PTC is in effect; they allow for smoother train handling.

All are mutually exclusive to a point.

Above is correct, in cab signal territory, you must still have a cab signal leader if PTC is cut out.

PTC is not cut out with *any* problem, only a failure that can not be fixed by be help desk. Some issues are resolved by a reboot of the PTC computer, others not so much.

All modern UP engines are dual ATC/CCS cab signal equipped.

CNW cabs have 3 aspects (green, red then yellow) on the ADU plus a motion light that turns on above 9?mph.

I don’t run on the CNW side so I couldn’t tell you how they actually work in the field.

My understating from guys I know in eh east is the LSL is used for the freights on the amtrak trackage to limit speed to 60mph. It would have zero to do with DPU operations.

My guess is that a breaker for it was left on and/or never disenguaged when it was setup as a remote DPU.

DPU’s can be ran in the sync mode (follows throttle commands from the leader) and independent mode (controlled via keyboard commands) from the engineer.

Nothing LSL, cabs or PTC has anything to do with DP operation. When in remote mode the DP remote typically ignores anything that would cause a penalty application, but I have seen cabs improperly cut out that caused an issue on a remote.



Edited 1 time(s). Last edit at 01/10/19 19:23 by MP683.