Passenger boarding bridge

A passenger boarding bridge comprising:

• a rotunda connected to a terminal;
• a tunnel unit whose proximal end is connected to the rotunda, the tunnel unit being extendable and retractable, the tunnel unit being rotatable about the rotunda;
• a travel device that supports the tunnel unit and includes a pair of travel wheels configured to travel forward and backward, the travel device being configured such that a travel direction of forward travel of the travel wheels and a travel direction of backward travel of the travel wheels are changeable;
• a cab provided at a distal end of the tunnel unit, the cab being configured to be docked with an aircraft;
• and
• a determiner configured to, at a time before undocking the cab docked with the aircraft from the aircraft, perform a determination whether or not the travel direction of the backward travel of the travel wheels at the time is a direction within a smooth undocking range, wherein
• the direction within a smooth undocking range is a direction that avoids contact with the aircraft when undocking the cab from the aircraft, and
• the travel device is configured to be rotatable in regular and reverse directions about a rotational axis that is positioned at a center point of the travel wheels, such that a rudder angle of the travel device is changeable within a range of −90° to +90° with respect to a center line of the tunnel unit.