I'd always been interested in the locomotives used at the locks on the Panama Canal for both tensioning the ship during transit and for pulling the vessel through the lock basins. Some years back during email correspondence with the Canal Authority (who readily welcome requests for information) I asked whether the locomotives were US built Diesels or similar to which they replied and sent me details of the loco's which are Electric Locomotives running on a toothed track made in Japan by Mitsubishi and each one costing $2.6 million. Impressive machines. I found this History Channel short film on the subject.