page_title: Panama Canal locks
section_title: Mules
hierarchical_section_title: Panama Canal locks / Mules
caption_attribution_description: English: A mule is holding the MS Maasdam, a Holland America Line cruise ship, during a transit of the Miraflores locks in the Panama Canal. The Miraflores Visitors Center is visible in the background. Deutsch: Muli in den Miraflores-Schleusen des Panamakanals. Im Hintergrund das Miraflores Visitors Center
context_page_description: The Panama Canal locks are a lock system that lifts ships up 85 feet to the main elevation of the Panama Canal and down again. The original canal had a total of six steps for a ship's passage. The total length of the lock structures, including the approach walls, is over 1.9 miles. The locks were one of the greatest engineering works ever to be undertaken when they opened in 1914. No other concrete construction of comparable size was undertaken until the Hoover Dam, in the 1930s.
  There are two independent transit lanes, since each lock is built double. The size of the original locks limits the maximum size of ships that can transit the canal; this size is known as Panamax. Construction on the Panama Canal expansion project, which included a third set of locks, began in September 2007, finished by May 2016 and began commercial operation on 26 June 2016. The new locks allow transit of larger, New Panamax ships, which have a greater cargo capacity than the previous locks were capable of handling.
context_section_description: From the outset, it was considered an important safety feature that ships be guided through the lock chambers by electric locomotives, known as mulas (mules, named after the animals traditionally used to cross the isthmus of Panama), running on the lock walls. These mules are used for side-to-side and braking control in the locks, which are narrow relative to modern-day ships. Forward motion into and through the locks is actually provided by the ship's engines and not the mules.   A ship approaching the locks first pulls up to the guide wall, which is an extension of the centre wall of the locks, where it is taken under control by the mules on the wall before proceeding into the lock. As it moves forward, additional lines are taken to mules on the other wall. With large ships, there are two mules on each side at the bow, and two each side at the stern—eight in total, allowing for precise control of the ship.
  The mules themselves run on rack tracks with broad gauge, 5 ft, to which they are geared. Traction is by electric power, supplied through a third rail laid below surface level on the land side. Each mule has a powerful winch, operated by the driver; these are used to take two cables in or pay them out to keep the ship centered in the lock while moving it from chamber to chamber. With as little as 2 ft (60 cm) of clearance on each side of a ship, considerable skill is required on the part of the operators.
  Smaller vessels, such as small tour boats and private yachts, are taken as handline transits, where mooring lines to the lock walls are handled manually by line handlers on the ship.
caption: A mule in action at the Miraflores locks.
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