At Ribble Valley Live Steamers, we have a raised track which accomodates 2 1/2", 3 1/3" and 5" gauge engines. Below is some information about each gauge:
2 1/2" Gauge
The following is taken from the 2 1/2" gauge society's website, the link to which is in "Useful Links" - "National Organisations":
Sometime around 1900 a set of track gauge standards was formulated. Thus tracks with a dimension of 2.500 inches between the inner rail edges was designated "GAUGE 3". At that time, this gauge was fairly popular for garden or scenic model railways, with the engines using clockwork or meths powered. Certainly none of them were capable of hauling the driver, let alone a driver and passengers ! Such capabilities arose from the work of (arguably) one man, Lilian (Curly) Lawrence, who wrote under the pen name of LBSC. Initially, the scale used for standard gauge locomoltives was half inch, but this was changed to 17/32-ins. (about 13½mm) very early on. A typical loco and tender is 3ft long, and looks very large when stood next to OO or O gauge models.
3 1/2" Gauge
This used to be a very popular gauge, but new models are tending to use this as the basis for a Narrow Gauge subject, which results in a loco similar in size to 5 inch gauge .
No doubt the popularity of this gauge was due to the fact that a standard scale loco could be built with modest workshop facilities. None of the components being particularly heavy, nor are they so small that they call for very precise work.
Depending on the type of loco modelled, they can haul up to 5 passengers.
Even a fairly large 3.5 gauge loco can be comfortably handled by one person.
This gauge is becomming increasingly popular, as it provides a locomotive powerful enough to haul up to 15 passengers, either on a ground level or raised track.
The equipment required for it's construction is within the resources and capabilities of the great majority of model engineers.
As a rough guide, a small 5 inch tank locomotive could be lifted on to the track by one person, while it would need two to handle engines any bigger.