What is Track direction/ alignment ?

What is Track direction/ alignment ?

Track direction/ alignment refers to the projection of the center line of the railway track on the horizontal plane, indicating whether the track is straight on straight sections and smooth on curved sections.

The position of the track center line should ideally match its design position. However, during the operation of locomotives and vehicles, the track on straight sections is not perfectly straight but consists of many wave-like plane curves, with a curve length of approximately 10-20 meters. These curves are not easily visible to the naked eye due to the large curve radius.
These curves occur due to the lateral horizontal forces exerted by the wheels, causing lateral displacement of the track. The lack of straightness in the track can lead to the train's serpentining movement.

Compared to track gauge, the alignment of the track is often more critical. As long as the alignment deviation remains within an acceptable range, changes in track gauge will not have a significant impact on the vehicle.