Budd RDC question

In my 1965 PRR employee timetable is the following note about operating Budd RDC cars:

When stopped on sanded rail under emergency conditions RDC (Budd) car or cars must immediately be moved forward or backward a sufficient distance to get at least one truck length off the sanded rail.

Does anyone know the purpose of this rule? The only thing I can think of is that maybe the sand interferes with the wheels being detected by the signal circuits.

correct, the RDC only had disk brakes so emergeny stops made you disapear from signal circuit.
most railroads pretty much have same rule for single lite engine moves.