From: ahk@chinet.com   
      
   Stephen Sprunk  wrote:   
   >On 08-Feb-16 20:04, Clark F Morris wrote:   
   >>Michael Finfer  wrote:   
      
   >>>As for PTC, there's no reason for it to degrade on time   
   >>>performance. The schedules will have to be lengthened.  That's   
   >>>something that NJ Transit excels at.   
      
   >>At least on the corridor since NJT and AMTRAK are going from one   
   >>form of automatic train stop with cab signals to a more sophisticated   
   >>form, why should there be any need for lengthening schedules?   
      
   >Because that's not what's actually happening.   
      
   >PRR cab signals were advisory and had _serious_ limitations that an   
   >engineer could understand and compensate for.  ACSES enforcement does   
   >not do such compensation, which means lower speeds in general.   
      
   Where the hell do you get that from? Pennsy signals certainly did   
   enforce speed. The limitation was that the speeds enforced were very   
   specific, five choices as I recall.   
      
   A signal is NEVER advisory. Lack of automatic enforcement does not make   
   a signal advisory.   
      
   >The main exception is where cab signals were lowered in the past in a   
   >crude form of civil speed restriction, and ACSES separately enforcing   
   >the latter (and with far better granularity) allows returning the cab   
   >signals to their proper speeds.  There are similar problems with   
   >high-speed switches.   
      
   >For instance, a long 125mph block with a short 90mph curve might have   
   >its cab signals artificially limited to 45mph.  ACSES can enforce 90mph   
   >for just the curve, so trains can return to 125mph as soon as they exit   
   >it rather than waiting until they reach the next block.   
      
   So shorten the block if it's necessary to have a speed restriction just   
   through the switch.   
      
   >While not not part of ACSES per se, at the same time Amtrak inserted   
   >several new speed codes between 45mph and 125mph, so what used to be a   
   >45mph block might now be a 60mph, 80mph or 100mph one.  This allows   
   >shorter blocks, which means higher speeds and lower headways without   
   >compromising safety.   
      
   There you go.   
      
   --- SoupGate/W32 v1.03   
    * Origin: LiveWire BBS -=*=- UseNet FTN Gateway (1:2320/1)