text: This invention relates to transport systems and, more specifically, to guest conveyance systems for amusement park rides and the like.
  In amusement park settings, a variety of transportation systems are utilized for conveyance purposes. In an amusement park, a guest conveyance system is used to move guests along a predetermined path through a ride or attraction. Such a guest conveyance system can include vehicles that are each equipped with one or more bogies, which are guides that slide along a track to steer the vehicle along the predetermined path. When one of the bogies slides along a curved section of the track, that bogie applies turning forces to the vehicle. These turning forces act in a direction perpendicular to the direction of the vehicle's travel. The vehicle also has a drive system that applies forces parallel to the direction of travel to increase and decrease the vehicle's speed as it moves through a particular ride. Such a drive system can include powered wheels and tires mounted under the vehicle to engage a horizontal surface adjacent to the track. The powered wheels are aligned to rotate in a vertical plane parallel to the direction of travel of the vehicle and thereby provide needed propulsive and braking forces as the vehicle moves through the attraction.
  One drawback associated with such an arrangement is that the wheels must be steered to avoid excess tire wear. If the wheels are not steered to maintain their alignment in a direction parallel to the vehicle's direction of travel, side slip forces from the bogies are applied to the wheels as the vehicle turns. These side slip forces cause the wheels to skid sideways as the vehicle negotiates turns, thereby resulting in undesirable wear and inflated power requirements for the drive system. Such tire wear is especially expensive because of the labor costs associated with replacing worn tires in an amusement ride having many vehicles. Further, such tire wear yields minute rubber particles that can accumulate within an enclosed amusement ride, requiring unwanted costs associated with removal of the particles by a ventilation system or by periodic cleaning of the accumulated particles from surfaces inside the ride.
  One solution to the above identified problem is to connect each drive wheel to a steering mechanism or provide an alternative drive system. See, e.g. U.S. Pat. Nos. 2,101,024 and 3,807,312. However, such mechanisms increase the cost of the vehicle and are also somewhat complicated, resulting in increased maintenance costs and more undesirable downtime.
  Accordingly, there is a definite need for a transport system having powered wheels that are each steered in an automatic, simple fashion to individually maintain their alignment in a direction parallel to a desired direction of travel to reduce side slip and tire wear.