What is TOB?

[Vince Black]

Hi, I downloaded a PDF file with BNSF Timetable and there often occurs "TOB" term (probably abbreviation). I have no idea what it means. It is used at speed maximum chapters, for example "Clovis to MP 178.5, including trains 100 TOB and over ............. 49 MPH" or "Train does not average more than 80 TOB".

Of course it couldn't be total train weight, maybe it's average car weight or something like that... 

[CSSHEGEWISCH]

TOB means "Tons per Operative Brake"

[Vince Black]

Thank you!

[Overmod]

Keep in mind that there are a couple of different formula definitions for what an 'operative brake' means, and that it doesn't apply to a virtual number of axles as power ratings do.  You will find these in a given railroad's special systems information (see the recent example Jeff Hergert posted).

Basic formula, for cars with typical 'foundation' braking where one brake cylinder actuates shoes on all eight wheels, is to treat operative brakes as the number of brake cylinders.  Some cars are constructed differently, such as container well cars and some tank cars; BNSF for example then considers the number of brake control valves instead of physical cylinders in the calculation.

Note that when you leave a terminal all the brakes are supposed to be 'operating' but some may fail enroute and have to be cut out.  (ECP by the way can do this remotely and 'electrically')  When this happens the TOB has to be recalculated and this may have consequences for dispatching and routing.

There is a thread I think you will probably find valuable on TPA and TOB here:

http://cs.trains.com/trn/f/111/t/221203.aspx

[jeffhergert]

Here's that link to the system special instructions.  TPOB (we use the 'P' for per in our abbreviation) instructions are item 2-F, found under speed restrictions.  There's aso a chart for determining how many brakes are on intermodal multi-platform cars.

 https://www.up.com/ert/ssi.pdf 

Jeff