Q:Given the following passage  "New Haven Harbor is home to the Port of New Haven, a deep-water seaport with three berths capable of hosting vessels and barges as well as the facilities required to handle break bulk cargo. The port has the capacity to load 200 trucks a day from the ground or via loading docks. Rail transportation access is available, with a private switch engine for yard movements and private siding for loading and unloading. Approximately 400,000 square feet (40,000 m2) of inside storage and 50 acres (200,000 m2) of outside storage are available at the site. Five shore cranes with a 250-ton capacity and 26 forklifts, each with a 26-ton capacity, are also available.",  answer the following question. Note that the answer is present within the text.  Question: Within the boundaries of the rail transportation, the switch engine used is privately owned.  What is it used for at the Port of New Haven?
A:
yard movements