What was the issue?
Australian Standard AS1742 Manual of Uniform Traffic Control Devices Part 7 provides a method of calculating the sighting distance required to safely proceed at passive level crossings.
At the upper end of the sighting distances proposed (notionally greater than 750 metres) there was industry concern around whether or not a driver would be able to reliably identify a train and assess its rate of approach (i.e. speed) in order to take an informed decision regarding whether or not it would be safe to proceed across the level crossing.
What was done?
Field collection and analysis of data to assess sighting distance at which train becomes identifiable.
Estimation of the rate of approach of that train at distances greater than 750 metres (and up to 1500 metres).