Track Geometry

Figure 2-21. Track frog and guardrails.

b. Track Geometry.

Track geometry includes such items as gauge, line, surface, cross-level, superelevation,

and profile. Every member of a train crew should be on the lookout for signs that the track

geometry is unsafe. The simplest example is wide gauge that could cause a wheel drop

derailment. Wide gauge often exists where tie condition is poor, where several spikes in a row

are missing, or in curves. It can often be spotted by wear marks in one of the rails that only

extend partway across the rail. Several low joints in a row can be a serious track geometry defect

if it sets up conditions for harmonic rock and roll, and consequently a wheel lift derailment.

Although these and other types of cross-level defects are often hard to spot, if the train is

observed closely, its motion can often indicate a situation that should be reported. Figures 2-22

and 2-23 show how the measurements of gauge and cross-level are made.

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