Here's a tutorial on how to build a railroad crossing signal for your LEGO train layout. This video looks at the construction of a modern cantilever signal that is common on many railroads especially in Florida. This model has been added to my ongoing display at Gold Coast Railroad Museum in Miami, FL.
All parts are available as LEGO system parts, and can be acquired on one or more of the following sites: Bricklink, LEGO Bricks and Pieces, LEGO PickABrick.
PM me or comment if you need specific part numbers or have any questions about the build process. I know it's a tedious video and a complex build, but the ends justify the means. :)
Music: incompetech.com
Note: Accidentally mentioned the 3L Axles in the Overhead portion twice, they are only to be installed once.