The following motor vehicles are exempt from the general prohibition contained in § 73.16:
(A) Military, fire, emergency, or law enforcement vehicles used for official or emergency purposes;
(B) Vehicles authorized by permit, lease, or contract;
(C) Vehicles owned by private persons engaged in the upkeep and maintenance of the trail systems under the direction of the local unit of government that manages the trail;
(D) Vehicles registered to or operated with the permission of a land owner on whose lands the trail system has been constructed, but only with respect to operation on the land of that owner;
(E) Motorized wheelchairs or other motorized devices operated by an individual who is physically disabled; and
(F) Temporary closing for aircraft crossing where permitted by City Council by use of gates and stop signs.