"Vehicles" or vessels travel on the infrastructure. Vehicles include cars, trucks, trains and airplanes. Vehicles are usually designed by mechanical engineers. Vessels include boats, ferries, and barges which travel on canals and use docks and seaports. In the same way that trains use train stations, airplanes use airports. In the same way that trains use railway lines (train tracks), airplanes use flight paths and then fly in the sky.