This wheel module is a “Driver.”  The tip-off is the number of hydraulic hoses leading to the center of the axle.  The wheels have in-hub hydraulic drive motors.  Typically two of these driver modules will be located on diagonally opposed corners. This arrangement allows the torque to be applied evenly for both longitudinal and lateral travel.  There will normally be two driver modules and two to ten idler modules that equally share the load on large transporters. If ramps or other conditions are involved that will require additional torque effort, additional driver modules will be strategically located.   For newer, "differenctial steered" units, all if the axle assemblies are drivers.