I was reading the track charts for NS’s Piedmont division, and I was wondering, what exaclty are “test miles?” They appear to have on at each end of the double track sections. So…what exactly are these?
Thanks!
I could be wrong but I do believe it is a “point A -B” marked mile to test the distance counter on locomotives to make sure it is on or near the 5280 feet. I could be wrong … but I know its used for that.
I don’t recall any distance counters on locomotives in my time however; we used “test miles” to check the accuracy of the speed indicator on locomotives using our watches. Test miles are measured miles. Most mile post markers are not exactly a mile unless measured.
You see them from time to time on highways as well. Often labelled as a “measured mile.” I’d bet that most of them are on fairly straight sections, so as to reduce/eliminate curve errors.
A test mile is a measured mile (5280) so the engineer can check the counter and speed, as trains are measured in feet so I know if the counter is accurate I know when my train is all the way in a sideing or crossedover on another main track or in the clear on a yard track.
Rodney
Rodney, when they give you the train length, is that without slack, bunched or some nominal value?
The train length is computed by adding the lengths of the individual cars, which is over the pulling faces of the couplers–this suggests that the length is of cars coupled, with the slack stretched. Additionally, on the UP, lengths are rounded up to the next even foot, so you get quite a safety factor in computing the length (the error is on the side of caution).
the test mile or measured mile is used for checking speedometer. it is put where you can keep your speed steady regaurdless if its on a curve or not. at 50 mph it takes 72 seconds to make a mile. times are listed in time table.