A major component of Bailey Yard is the East Hump, where every day, more than 1,500 rail cars are sorted, taken off one train, and re-routed to another. Locomotives push the cars up a 34-feet-tall mound, where they are then separated and sent downhill, one at a time, onto one of dozens of "bowl" tracks -- each of which represents a specific eastern destination.
A corresponding West Hump is also used to used to sort cars heading west, but because most traffic heads east, the bulk goes through the East hump. In addition, the West hump mound is only 20 feet high.
Locomotive number Y823 slowly pushes rail cars uphill towards the West hump. Because many westbound cars are empty, or at least carrying lighter loads than their eastbound counterparts, less locomotives are needed to push the cars towards the West hump than for the East hump.
After the cars are separated, they roll gently downhill using only gravity toward their designated bowl track. When they pass a so-called "retarder," their wheels are squeezed hard enough to slow them down so that they roll easily and safely onto the proper track for their eventual destination. A computer routes the cars onto the proper track.
A closer look at a retarder, which is used to slow the railcars down as they roll unimpeded downhill towards their designated bowl track where they will connect with their intended train at 4 miles an hour or less.
Often, when trains come into Bailey Yard, their rail cars are separated from the locomotives and are sent off to one of the humps to be re-directed to trains heading to their eventual destination. While that happens, the locomotives are brought to the diesel yard to be serviced.
Though Bailey Yard is off limits to the general public, visitors can climb the Golden Spike observation tower, where they can get a panoramic view of the world's largest rail yard. From the top of the tower, they can see rail cars all the way to the horizon.
Many rail cars that roll through Bailey Yard have damaged wheels that must be replaced and repaired. Here, near the maintenance area, dozens of train wheel axles are lined up in preparation for being used as replacements.
Many locomotives heading east are sent through the East service track, where they are loaded up with, among other things, sand that they will use to gain traction when their steel wheels slip on the steel tracks. The sand is shot onto the tracks using nozzles mounted at the wheels.
This special facility -- the only one of its kind in the world -- is designed to inspect railcar wheels for small defects that would otherwise be invisible to the naked eye. Special ultrasonic sensors inspect each wheel to determine if there are problems that need maintenance.