Methods of Control – An introduction
Tuesday, April 6th, 2010
Hi all – Welcome to my first contribution on Railsexy! A little about myself, I’m a former railroader, having worked as a Rail Traffic Controller for a major Canadian railway. I got laid off, and well.. I decided not to return and instead pursue a career in a different field. I hope that my insight will help the visitors of this site to get a better idea of what goes on :)
A railway, at its most basic level, consists trains traveling from point A to point B. It seems basic enough, and when you’re only running one train on a line, you aren’t going to have any issues regarding the control of traffic. However, since time on rails is money, it makes most financial sense for a railway to operate many trains on a piece of rail between point A and point B. Almost immediately after someone invented the idea of running more than one train at once, it was discovered that trains on the same line might crash into each other if a method of control wasn’t developed - in short, someone needed t make sure the trains don’t touch each other.
I could go into the many methods of control invented over the years to keep the trains safely apart, but I’ll save that for another entry. The most primitive and effective method to keep the trains from touching is only allowing one train into a certain area at once. This works well in very rarely used areas, and a form of this type of control is still in use today (We’ll get into that when we talk about OCS). It isn’t the most effective way of operating a railroad, though – which is why a way to safely control many trains at once is required.
Let’s say you’ve got two towns: Alphaville and Zipperville. These are two bustling towns with industry and people about 400 km apart. The two towns decide to make trade easier by constructing a railway between them. Initially there is only one train operating on the entire line, so there’s no risk of any collision accidents.
The train starts in Alphaville in the morning, and arrives at Zipperville about seven hours later, and returns back to Alphaville the next day. The railway is well used, the people are happy and industry is flourishing. The line is so well used, however, that towns spring up along the line to mine local ores and access the forestry resources in the area to be shipped to Alphaville and Zipperville. The line becomes so busy that the towns add a second train to the line. One train will carry only freight, while the other train will carry passengers. Terminals and switching yards are built at Alphaville and Zipperville, as both towns grow to become important economic and industrial centers.
Because the trains will be operating at different times, different speeds, in different directions and will be making stops along the way, a method of control is required to make sure the trains not only are able to operate safely, but profitably as well. Because it was prohibitively expensive to lay a second track along the entire 400 km route, trains must be able to share the tracks with each other, even if they are heading directly towards each other! Passing tracks, called sidings, are therefore required. In this line, three sidings are constructed: one at Southton, one at Middlesburg, and one at Northton. The sidings are constructed long enough so that most trains operated on the line can fit inside of them. The reason for this will be made clear, and future editions of this series will show what happens when a train is too long for a siding (it happens quite a bit in the real world, which is why the RTC makes the big bucks!!)
A siding is little more than a ‘passing tracks’ that allow either overtaking or head-on trains to pass. In the old days, pretty much every town had a station and a siding. Today, many of these towns exist only in the names of existing sidings, station name signs and locations on Employee Timetables. Siding-based single track railroading is the bread-and-butter of modern railroading — most railfans who live in cities such as Toronto, Calgary or Montreal have never witnessed a ‘meet’ in real life – they do exist, and account for probably 90% of all railroading in North America. Methods of control dictate when and how trains meet, who gets put in the siding, and how this information is relayed to the crew. In Canada, there are two main methods of control: the Occupancy Control Sytem and Centralized Traffic Control.