The shape of a railway track in plan and profile, plus the cant between the rails, within tight tolerances: what designers set and maintainers keep.
Track geometry is the shape of a railway track: its horizontal alignment, its vertical profile, the gauge between the rails, and the cant (the height difference between the rails on curves). Designers set it, and maintainers measure and correct it throughout the railway's life, within tolerances of millimetres.
Track designers set the geometry to the line speed and the trains that use it; structures, platforms, overhead line equipment and signalling are designed around it. Clearances are checked against the space the moving train needs (the gauge profile or kinematic envelope), which depends on cant and curvature. In IFC 4.3, alignments carry cant, so models can position elements against the true track geometry.
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