Track is often surveyed many months before a rail renewal takes place. after the survey is complete, any maintenance work carried out in the vicinity can require a costly repeat survey.
Painting a clear narrow line along the head of the rail notifies maintenance teams of the precise area of forthcoming works.
Once the work is complete a black line can be painted over the yellow to indicate that routine maintenance may now recommence.
Other applications include the application of track lubricant to the head of the rail.