Most likely the two rails on the left both use the rail on the right. Live steamers and other riding-type model trains come in several different gauges. My guess is this is for 4-3/4" gauge and 7-1/2" gauge, and it appears the train shown is on the 4-3/4" gauge which works out to about 1:12 scale (one inch equals one foot).
You can check out the Ottawa Valley Live Steamers and Model Engineer's website at http://www.trainweb.org/ovlsme/ . WJSTIX is correct about the use of the rails, and discoverlivesteam.com has the club's gauges listed as 3.5", 5" and 7.5". The track in the picture is 5" and 7.5", I believe the 3.5" is a separate, elevated track. IMHO, it would be very difficult to make a three rail track work for G scale trains and a rideable size of train, either 5" or 7.5", due to the difference in the size of the flanges and tread width. I'm not saying it's impossible (that would just invite someone to prove me wrong ), but I've never seen or heard of it being done.
- James
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