From: ce11son@yahoo.ca   
      
   On Thu, 19 Jun 2014 10:23:38 -0700, Nobody  wrote:   
      
   >On Thu, 19 Jun 2014 00:00:19 +0200, Marc Van Dyck   
   > wrote:   
   >   
   >>bob brought next idea :   
   >>>   
   >>> I do wonder the extent to which power independence is useful for a tram,   
   >>> though. On a trolleybus, the utility is clear, but if you need tracks to   
   >>> run a tram on, the restrictions of being tied to an overhead wire are not   
   >>> significant. The only use case I can see for them is in locations where the   
   >>> visual intrusion of overhead power is undesirable.   
   >>> Robin   
   >>   
   >>A second possible usage is at crossings between different transit   
   >>systems, for example a tram line and a trolleybus line.   
   >   
   >I've wondered how Yarra Trams in Melbourne handles that situation,   
   >where its system crosses tracks of the region's electrified heavy-rail   
   >network.   
   >   
   There is a description in :-   
   http://en.wikipedia.org/wiki/Trams_in_Melbourne   
   (Tram/train level crossings)   
   The mechanical bit is probably the simple part of the design with the   
   electrics requiring various interlockings so that the appropriate   
   single voltage is applied to the entire assembly above the crossing to   
   match the "open" route. This only goes up to 1500v which is possibly   
   not that disastrous for the trams if it is accidentally applied in the   
   short term but ISTR there are (or used to be) installations in   
   continental Europe involving 15kV or 25kV on the railway;   
   http://railforthevalley.wordpress.com/2010/05/11/when-trolleybus   
   and-streetcar-cross-paths/   
   mentions Suhr in Switzerland (1200V DC v. 15kV AC) and has a   
   photograph of a train/trolleybus crossing in Russia.   
      
   http://www.youtube.com/watch?v=v_hNE2NUbCE shows one of the Melbourne   
   level crossings including another necessary feature of hingeing the   
   half-barriers to prevent them touching the tramwires.   
      
   > has in recent years posted several photos of at   
   >least one at-grade crossing to .   
   >   
   >Unfortunately, Giganews seems only to have archived the past 12 months   
   >and none of his postings in that time show the example.   
      
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