From: jock@soccer.com   
      
   On Thu, 19 Jun 2014 21:54:09 +0100, Charles Ellson    
   wrote:   
      
   >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-trolleybu   
   -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.   
   >   
      
   Thanks.  The Mellie isolation section makes sense, even to me!  It's   
   interesting that the trams run with the panto elbow facing to the   
   rear.   
      
   And in looking at all the info you pointed to, it reminded me that   
   Wellington, NZ's last few tram routes co-existed with the city's large   
   trolley bus network in the 50's and early 60's, especially as they   
   were (still are) concentrated on four major streets in the CBD.   
      
   --- SoupGate/W32 v1.03   
    * Origin: LiveWire BBS -=*=- UseNet FTN Gateway (1:2320/1)