by Wdobner
benltrain wrote:It actually is allowed, in an application a good deal more complex and with trains far less manuverable than what Phil and Matt are describing. The system is called HelperLink and is used by BNSF and Montana Rail Link, and was used by Conrail shortly before they went defunct. I don't know whether Union Pacific, Kansas City Southern, Norfolk Souther, or CSX also use these devices but clearly it is possible and the FRA allows it, at least with freight operations.Nasadowsk wrote: I believe the ICE does quick uncouples at stations, though not moving. Ther'es really nothing magic about this, the technology is simple, it's just regulatory crap preventing it in the US.Bingo, again, this is the reason why this just won't work. FRA would never allow this. We need a more conventional approach, because of the FRA and SEPTA both being very stubborn (for lack of a better word).
Clearly a passenger rail application would be a bit different from what the BNSF engineer, Mr. Krug, describes in the link above. For one thing as has been illustrated by the discussion of the IC3 the need for a radio controlled air pipe is unneccesary, and since it'd presumably be an automatic coupler so is the pin puller. Whether the rear section of the train would be allowed to proceed at 20mph in CTC territory would be up for grabs, since SEPTA doesn't quite have the pull that BNSF does. With something like Communications Based Train Control, where block sizes are arbitrary the two trains could be in their own blocks, and presumably if the front section goes into emergency the rear section would recieve a stop indication and also go into emergency.
As an example on SEPTA's network say a combined DMU/EMU train is leaving Pennbrook for Lansdale. Somewhere just south of Lansdale the (say) front EMU section and rear DMU section separates. The EMU train continues on at 30 to 40mph while the DMU section slows to 20mph until they're in the next block back. The EMU section, which is either running to Doylestown or terminating at Lansdale would take the diverging route just south of Main St and follow the line to Doylestown. That switch would reset for the line to Quakerstown and the DMU section would continue through and stop at the former mainline platforms. It's possible that the EMU section would wait around for the DMU section to catch up at Lansdale, but really that's quite unneccesary. The train would undoubtedly have a functioning PA system, and would certainly have conductors who could walk through the train and inform passengers, especially those they might remember as holding tickets to Quakertown, Sellersville or others that they need to walk forward or backward to reach their destination. Holding lead section at the station for passengers transfering from the trailing section would pretty much negate any benefit an on-the-fly separation would bring. The same scenario could be worked out at Norristown, Fox Chase, or Wawa (assuming the R3 West Chester comes back and an extension to Kennett Square or Octorara is built).
Of course on the fly coupling would still have to be worked out. I have no clue what the FRA's rules are regarding that operation, but I'd be inclined to think it's fairly well prohibited. It's quite possible that one section would have to be scheduled to arrive a few minutes ahead of the other and the coupling would have to be done with one section stationary there for it to work.
