What are the small vertical sections of rail that can be seen embedded in the trackworks or a little distance away from the tracks every so often?
These small vertical pieces of rail (or other structures such as a small cement post), usually painted yellow or white, are monuments or vertical datum indicators. They have marks on them that indicate the correct intended height of the rail head at that location on the track. When track maintenance crews adjust track for its level, they use these indicators as the reference to which to adjust the rails. (Of course, other considerations apply in special cases such as at curves, where the track’s cant has to be taken into consideration.) These indicators are also used to measure the longitudinal movement of long welded rails. The indicators are usually buried quite deep into the earth so that they do not shift around easily. Sometimes the track level is indicated painted on a nearby permanent structure instead. There are also water level indicators in some areas, which are upright pieces of rail with graduated markings on them in red, yellow or light green, and dark green. These serve a
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