This is one of the "mules" that help the big ships through the locks. The mules are locomotives that cost around $2.5 million each (the canal authority has around 100 of them). They run on tracks and are driven by a rack and pinion system where a gear in the mule engages a rack that is located between the tracks. This gives the mules a lot of traction when they are pulling a ship through the locks. The mules provide about 30% of the energy needed to move the ship. The rest comes from the ship's propeller. The radio chatter from the pilots to the mule operators is constant as the pilot on the ship tell the operators how to tension the steel cables that keep the ship centered in the locks.
Added 6 June 2009