Some ideas are stupid ideas. Some ideas are b* stupid ideas. Using the staff circuit to prove the operation of the direction relays in a set of flashing lights, or that an intermediate siding is secured normal, is, IMHO, an example of the later.
The purpose of the electric staff system is to prevent collisions of trains, particularly head on collisions. You don't get more important than that.
But if the Direction Sticks aren't proved in the Staff Lines, then how else can this be done? And it must be done some how or another.
Looking at Ordinary Staff sections where there were no staff linewires to prove in, the solution was to install 1 pair of wires to the station at one end of the section or the other, which illuminates a light that the train crew have to check. A pair of wires to both ends of the staff section, would of course increase the cost, though it improves safely.
More recently, level crossings in NSW have (all/mostly) been monitored to a centralised location such as Junee or Broadmeadow. The monitor has 16/32 channels, and links to the monitoring centre via a Mobile Phone type system. The 16/32 channel system supervises all/most of the most important parameters such as:
* Battery Charged (12VDC with lights only, 15VDC with booms)
* Battery Charger Active (120VAC)
* Other Power supplies, if any.
* DXT, XT, UXT, etc., track circuits
* DDSR, UDSR direction sticks
* XR crossing relay (turns on Flashing Lights when deenergised)
* XPR crossing repeat relay
* Lever Frame Relays
* Main Line Indicators??
* Boom R??, if provided.
* Door Locked Properly (in WA at least)
* Reset circuits with Axle Counters?
At the Supervising Centre, some kind of data recorder (black box) presumably records every thing that goes on.
At the Supervising Centre, some of the indications are displayed or even integrated with the Signalling Control Panel.
Monitored level crossings have unique ID numbers, rather like Traffic Lights.
Tamworth, Brisbane Street (ID506) http://www.sa-trackandsignal.net/Pdf%20files/NCRN/JH1562.pdf
Railway signalling "normally" proves relay down,
* Normal and Reverse Point Indicating relays, NWKR and RWKR and their repeats are cross-proved
** If points are Normal, the Reverse Relays must be down, and vice versa.
* difficult/impossible to do with Track Circuit Relays, so other measures are needed.
* difficult to do when relays are not in the same location, such as TR and TPR track indicating relays.
* proving level crossing relays in the staff lines make perfect economical sense.
* Tunnel Stick relays such as Marangeroo failed when trains traversed Tunnel in reverse direction during SLW.