The Circle Subdivision is a relatively short subdivision on BNSF's Montana Division. It is just over 40 miles from Glendive, MT, where it begins, to Circle, MT, where it ends. The reason I chose this is because the timetable occupies just one page and does not contain a ton of elaborate and complicated information, which will make explaining it a bit easier. At the moment, the subdivision is out of service almost completely, so all the information is irrelevant. If it is put back into service, or if a dispatcher instructs a train to use it anyway, the information will still be valid and important.
First, let's take a look at the timetable page for the Circle Subdivision:
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Well, let's go over this, starting with Item 1. Before we even get to Item 1, there is a table with general information. This varies in size by the size of the subdivision. In this table, there are just two stations, Glendive and Circle. On other subdivisions, there could be more than two stations. In this case, a station is any named point along the railroad, not necessarily where passengers could board a train. To the left of the station names, you have the mileposts they are located at. Milepost zero is located right out the back door of the depot in Glendive, and from there, the mileposts count up to 50.0, at Circle. To the far left is the length of the siding in Circle, in feet. Again, if there were more stations, or more sidings, more would be listed in that column. Glendive has a yard, which, for the purposes of the timetable, is not considered a siding, although technically a yard is made up of several sidings. To the right of the station names is more information. The letters "BJT" in the Glendive row, indicate that (B) Glendive is a place where track bulletins and circulars may be acquired, (J) Glendive is a junction, and (T) Glendive has a turning facility, such as a turntable or wye. In the case of Glendive, it actually has both.
Moving down the left column, we get to Item 1, which is labelled "Speed Regulations." The first regulation, in part A, is always the maximum speed. On the Circle Sub, that is pretty simple. The whole thing is 10 mph. If this were a Main Line, instead of a Branch Line (see above the table), chances are the speed limit would be higher, and it would likely have several maximum speed limits, and possibly a passenger maximum and freight maximum. Below that, in part B is permanent speed restrictions. Speed restrictions are any location where the speed is less than the maximum speed. Permanent restrictions are often in places where there is a curve, which will always be there, and always require trains to slow down. Seeing as the Circle Sub has a maximum of only 10 mph, there is nowhere that any trains would have to go any slower. Temporary speed restrictions, which would not be listed on the timetable, are areas where there is an unusual track condition, requiring a lower speed, such as track work. Those are listed in the track bulletins, and they change as track conditions change. Part C lists switch and turnout speeds. This is the speed a train must pass over a switch if it is taking the diverging route. Trains do not usually need to slow down for the straight route through a switch. Part D is any other speed restrictions. Sometimes there will be a bridge with tight clearances that requires high or wide loads to slow down, just to prevent them from swaying into the bridge. That sort of restriction would be found in part D. Again, since the maximum speed limit is so low on the Circle Sub, there really are no other restrictions.
Item 2 on the timetable is the weight limits. Bridges and track have different weight limits, depending on the construction and maintenance. In this case, the maximum car weight is 143 tons. Restriction G is additional restrictions based on car length. Very often, sorter cars are required to be lighter than 143 tons, but how much lighter varies by the restriction letter. The specifics of each restriction letter can be found in another document called the System Special Instructions. An additional restriction, specific to this subdivision, is listed below the weight restriction. It states that six axle locomotives and derricks are not permitted past milepost 20.0 on the Circle Sub, which means if you had to go out to Circle, you would want to make sure all your locomotives had four axles and you had no six axle derricks in the train.
Item 3 goes over the type of operation. This varies by subdivision, and even varies within a subdivision. For the Circle Sub, it simply says "TWC," which stands for Track Warrant Control. To operate on the Circle Sub, a train must receive a track warrant from the dispatcher, which gives them authority to operate between defined limits that the dispatcher chooses. There are no signals on the Circle Sub, or that would also be noted on the timetable. An example would be ABS, which stands for Absolute Block Signals. Those would protect trains as they operated, but they would not give the train any authority. Other possibilities for type of operation are CTC, 2MT CTC, DT-ABS TWC, among others. (Check the glossary if any of these are unfamiliar to you.) One of these days I will go over the various types of operation, but that is a rather in depth and technical topic.
Item 4 is rules-specific items. In this case it talks about whistle usage and laws in the state of Montana, flagging protection, and rule 6.28, which covers speed again. Flag protection would be required on the Circle Sub if the train had to make an unexpected stop. This is to protect the train from having another train run into it. The timetable states that the Conductor would have to go back to a mile and a half behind the train to protect it from any other potentially approaching trains. Now in reality, if anyone were out there, chances are they would be the only train out there for months, but flagging is still required. On a line with signal protection, flagging is not required because the signals would protect the train instead of the flagger. Rule 6.28 adds to the 10 mph speed limit. It adds that the crew should be prepared to stop in half their range of vision, short of trains, engines, railroad cars, men or equipment fouling the track, a stop signal, or an improperly lined switch or a derail. This means, depending on the weight of the train and the visibility, the crew may actually have to move slower than 10 mph. They can only go 10 mph if the visibility and conditions allow them to stop according to the items listed above, and in rule 6.28.
Item 5 is track side warning detectors. Track side warning detectors warn trains of overheated wheel bearings, dragging equipment, rock slides, high water, and shifted loads. The Circle Sub does not have any detectors. Other subdivisions do. Some have just a few, and others have quite a lot of them. They would all be listed in this section, with their location and what type of detector they are. If they protected a bridge, tunnel, or structure, that would also be noted in this section.
Item 6 is where and FRA excepted track would be noted. FRA excepted track is where trains are required to travel less than 10 mph, and passenger trains are not allowed to travel at all. While this track has a low speed limit, is in poor repair, and almost never sees a train, it is not an FRA exception, and therefore is not FRA excepted track. Some subdivisions will have sidings or industrial tracks which are considered FRA excpted, and they would be listed, with their location, in this section.
Item 7 is for special conditions. These special conditions can be just about anything, unique to the subdivision, which will affect train operations. In this case, the Circle Sub lists a special condition for when the temperature is above 80 degrees. If it gets to or above 80 degrees, no trains are supposed to operate past milepost 7.0, except with the permission of the listed people. Also under special conditions, it is listed that the west switch in Circle is supposed to be lined for the grain elevator, because they actually own that track. It also lists how track warrants are to be addressed and the potential for a flash flood. Interestingly, the entire line is considered a flash flood hazard!
Item 8 is where line segments are listed. This really does not concern operations, but it is how billing is done when maintenance is performed on the subdivision.
Item 9 is simply general information about other locations. It will almost always give a location name, car capacity, and which direction you an switch into that location. Some locations will only have one switch, and so the train must be going a certain direction to have access to those locations. On the Circle Sub, all the other locations are accessible from both directions.
Item 10 is just a profile of the line. It is a grade chart, with the elevation on either end in feet above sea level. The numbers above the chart which say, "1.00E 1.02W" indicate the grade percentage. Eastbound trains face a downhill grade of 1%, while westbound trains face an uphill grade of 1.02%. I am not sure what accounts for the 0.02% difference of grade for the different directions, because this is all on the same track. That is actually a small margin though, I have seen some indicated farther apart on the same piece of track. Either way, those numbers indicate the ruling grade.
When you read a timetable, the west or south directions are always indicated as westward, and you read the tables and grade charts from top to bottom. East and north are always indicated as eastward, and you read charts and tables from bottom to top.
I hope all that makes sense. It tends to come together a bit after you have looked at several of them. I did edit some of the information off of the timetable, such as phone and fax numbers for the dispatcher, but that would only be a concern if you were in a station with a phone and had to call the dispatcher. Other than that you would simply contact them on the radio. I also left out the system numbers for sidings and stations, but that really does not effect the ability to read through this. I just figured that BNSF would appreciate not having all their information published, even if it is not really a big secret. The radio channel, as some of you may have notices is 76. Feel free to listen in if you are in the area. I will warn you though, if you are looking for activity on the Circle Sub, you might be disappointed. The last time a train went down there was about three weeks ago, and it went to milepost 6.0, because Glendive Yard was full and the dispatcher was desperate for a place to put the train. Before that it has probably been several years since anything went down the Circle Sub!
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