Abstract: In one aspect, a track structure usable by a wheeled vehicle for hauling a payload up an inclined enclosed passageway comprises a hollow rigid center rail member configured to act as both a center rail for the wheeled vehicle and as a ventilation duct. Opposite lateral faces of the hollow center rail member have respective wheel contact surfaces grippable by an opposed pair of inwardly-biased drive wheels of the wheeled vehicle. Rail support structure depends from the hollow center rail member. An elevated pair of rails is attached to the rail support structure, the rails being on opposite sides of and substantially parallel to the hollow center rail member. Each rail is supported by the rail support structure so as to provide an upper, lower, and lateral surface suitable for rolling engagement by a weight-bearing wheel, undermount wheel, and guide wheel, respectively, of the wheeled vehicle.

Abstract: In one aspect, a track structure usable by a wheeled vehicle for hauling a payload up an inclined enclosed passageway comprises a hollow rigid center rail member configured to act as both a center rail for the wheeled vehicle and as a ventilation duct. Opposite lateral faces of the hollow center rail member have respective wheel contact surfaces grippable by an opposed pair of inwardly-biased drive wheels of the wheeled vehicle. Rail support structure depends from the hollow center rail member. An elevated pair of rails is attached to the rail support structure, the rails being on opposite sides of and substantially parallel to the hollow center rail member. Each rail is supported by the rail support structure so as to provide an upper, lower, and lateral surface suitable for rolling engagement by a weight-bearing wheel, undermount wheel, and guide wheel, respectively, of the wheeled vehicle.

Abstract: In one aspect, a track structure usable by a wheeled vehicle for hauling a payload up an inclined enclosed passageway comprises a hollow rigid center rail member configured to act as both a center rail for the wheeled vehicle and as a ventilation duct. Opposite lateral faces of the hollow center rail member have respective wheel contact surfaces grippable by an opposed pair of inwardly-biased drive wheels of the wheeled vehicle. Rail support structure depends from the hollow center rail member. An elevated pair of rails is attached to the rail support structure, the rails being on opposite sides of and substantially parallel to the hollow center rail member. Each rail is supported by the rail support structure so as to provide an upper, lower, and lateral surface suitable for rolling engagement by a weight-bearing wheel, undermount wheel, and guide wheel, respectively, of the wheeled vehicle.