From: stephen@sprunk.org   
      
   On 11-Apr-15 11:08, Adam H. Kerman wrote:   
   > Stephen Sprunk  wrote:   
   >> On 11-Apr-15 08:36, Adam H. Kerman wrote:   
   >>> CTA discourages passengers from changing cars once they're on   
   >>> board.   
   >>>   
   >>> I agree in part and disagree in part. Platforms should be sized   
   >>> for expected boarding at the station, not the longest train.   
   >>> Passengers should be in the car with the doors that will open.   
   >>   
   >> ... but when you combine that with the above, that means passengers   
   >> are supposed to know _when they board_ what cars will allow them to   
   >> exit at the destination.  That isn't an issue for daily commuters,   
   >> but how are tourists or occasional riders supposed to know this?   
   >> It's simpler and more passenger-friendly to make all your platforms   
   >> as long as the longest train that stops there.   
   >   
   > I'm trying to reduce station construction costs on your railroad.   
      
   Platform height/length has a negligible impact on cost, compared to all   
   the other (much larger) station expenses that aren't affected at all.   
      
   DART raised every platform on the Red and Blue lines for <$100k/ea, in   
   less than a year.  Extending the short at-grade platforms would be a   
   similarly trivial exercise.   
      
   > Doesn't apply in the Midwest, but in hilly areas, you don't always   
   > have sufficient tangent track (without both vertical and horizontal   
   > curves) for a full-length platform and there's no reason to attempt   
   > to build one for a low volume stop.   
   >   
   > I'm very much opposed to "doing without" when we've raised costs to   
   > excessive levels or geography prevents construction because of   
   > one-size-fits-all rules that don't apply to the situation at that   
   > location.   
      
   Hancock was complaining about the cost of longer/higher platforms, not   
   genuine physical limitations.   
      
   > On Metra, they expect passengers to follow instructions. There are   
   > announcements with regard to which doors will open and which car the   
   > passengers must be in to get off the train.   
      
   Do they announce that at every station where you board, so that you know   
   which car to get on?  Or do they expect you to hear the announcement on   
   board and change cars at an intermediate station with a long platform?   
      
   >> DART's at-grade stations have 300ft* platforms because that was   
   >> the longest train they currently operate; however, they knew they   
   >> will eventually have 400ft long trains, so above- and below-grade   
   >> stations (which are expensive to alter) have 400ft platforms, and   
   >> the platforms at most* at-grade stations were designed to be easily   
   >> expanded.   
   >>   
   >> * That's the length of a city block in downtown Dallas, where DART   
   >> currently operates in the streets.  That section will be made   
   >> below grade someday, which will allow longer trains.   
   >   
   > If it's in subway,   
      
   It's not, today.  The latest plans I've seen have them dropping the   
   tracks into an open cut, which is cheaper than subway but still quite   
   expensive.  It's an open question whether they'll do that first for the   
   current route or for the new "second downtown" route.   
      
   DART's only subway is under US-75, which is itself below grade.  That   
   section includes one active station and one planned (but apparently   
   abandoned) station.  DART didn't have a choice in that case, but it's   
   clear that they don't want to repeat that elsewhere due to cost.   
      
   > then why can't trains be operated more frequently? You're no longer   
   > concerned with intersection capacity.   
      
   That is one of the reasons DART (and the City of Dallas) want to move   
   the trains below grade.  Trains have to stop for traffic lights, which   
   limits train length to the shortest city block.  The stations were   
   deliberately located on unusually long (400ft+) blocks.   
      
   The signal system limits train frequency for the rest of the system; as   
   it stands, they are already at headways of 2-3 minutes during rush hour,   
   with most trains "riding the yellows".  That is why DART wants 400ft   
   trains in the first place.   
      
   S   
      
   --   
   Stephen Sprunk         "God does not play dice."  --Albert Einstein   
   CCIE #3723         "God is an inveterate gambler, and He throws the   
   K5SSS        dice at every possible opportunity." --Stephen Hawking   
      
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