When the mileage is marked on a crossing control box, it is a form of a milepost, which shows the distance from the home station. However, as you go down the line, does this number show the distance between the control boxes, or between the crossings themselves? If it’s the latter, is this distance measured from the end of one crossing to the front of the next, or the end of one to the end of another?
::EDIT:: Addition to second sentence in order to clarify question
Neither. It shows the distance from Milepost zero on that particular line, or at least the distance from where milepost zero was when originally designated (in the event some of the line is abandoned) or in some cases redesignated after sale of the line or partial abandonment.
LC
…And then there are long and short miles (usually courtesy of line changes)…and most stencilled locations only show the milepost to one or two decimal places…and you have signal people who can’t read maps and/or track charts…and then you have things like the Denver Joint Line (Pueblo-Denver)where the BN guys and Dispatchers renumbered the mileposts in 2001. (The BN guys think backwards and they didn’t have enough fingers and toes to keep track of things[censored])
Gluefinger needs to someday get a timetable, a track chart and then go to the field where you still have dual/ bi-directional mileposts and equations…it’ll leave him spinning![(-D][(-D][(-D]
Er…shoot! I worded my question wrong…I knew that the MP marks the distance from the start station on the line…but I meant, to what position is the mileage calculated? To the crossing? To the control box?
The mileage is calculated to the position of the milepost itself.
If the railway company needs to locate a particular crossing, bridge, control box, switch, etc., it will refer to the nearest milepost(s) (eg: bridge located between miles 13 and 14); or (when there are many similar structures within a short distance) will erect an intermediate milepost near the structure with more exact mileage (eg: bridge located at 13.05 miles).
Milepost position is calculated and shown on the maps. The physical milepost in the field can be as much as a thousand feet off after getting knocked over with ballast regulators, jordan spreaders and who knows what else. Trying to place them back with the odometer of a highrail is dumb , but folksstill do it (those 19 inch rims are not what came on the truck when the odometer was installed).
In general, the map location used on wayside signs is the centerline of the track intersecting the centerline of the crossing surface (the centerline of the road is something else entirely)…It’s not that big a deal with decimal mileposts, you can be off 52.8 feet to 5280 feet easilly. It’s an accuracy vs. precision thing (and don’t tell a surveyor those two things are the same because they aren’t)
THE NUMBER PAINTED ON THE BOX IS WITNESS TO SOMETHING ELSE NEARBY.
in addition to the mileposts, a DOT crossing inventory number should be posted
either on the control box or strapped to one of the crossing signals. Often the milepost designation begins with letters indication a particular subdivision. Both milepost and DOT number are intended to aid in exact location. In the event of a train-vehicle collision these locations can aid emergency personell and record keeping by the DOT.
And I take it the railroads are too cheap to purchase the speedo correction equipment to rectify the problem?
Brush cutters also have a habit of slicing off mileposts, the railroad I worked for had a nasty habit of not replacing them after being sliced.
Randy