Alyth

Today, some people from the IS department took a tour of the Alyth switching yards. This is where trains from all directions get broken up and set into appropriate blocks to continue onto their destination. Each blocking track is up to 2400ft. in length, and up to four tracks can be used to create a new train consist. Some trains that run now are close to 10,000ft. in length. There are 45 blocking tracks in Alyth yard. It's all pretty complicated and neat to watch.


View to the west from Control Tower - downtown, repair shops and fuelling station in the background

Switching is affectionately known as 'humping' since the incoming trains are backed up into the blocking area and broken off the train one-by-one (or up to five at a time) just over the high point in the yard (the 'hump') and gravity rolls them into the correct block.


The "Hump"

A computer program called ProYard calculates the time required to roll a car into the correct position based on it's weight (which is weighed at the hump) and appropriately applies braking pressure at the retarders to allow the car to roll at the correct speed and connect with the cars already in the correct block. The computer also sets the right track switches for the car to go into the right block track based on the car ID that is scanned just as it comes into the hump.


Retarders and blocking tracks

Cars that roll through the retarders and have too much or not enough speed will either crash into the cars already in the block or stop before they reach the cars already on the track. Either situation can cause big problems, even derailments, so it's all closely monitored, especially in the winter when weather conditions can screw with the calculations of ProYard or affect the switches or retarders.


View to the Northeast

If you want to see and hear humping close up (not the good kind, the metal-on-metal kind, here is a video I took just before we left at ground level. It's probably a very good idea to turn the volume down on the Castpost client....