SNUBBER

Reduces or eliminates voltage spikes on long runs of DCC bus wire,this is especially important on any DCC track bus wire 40 feet [12 meters] or longer. 
Protects decoders from damaging inductive voltage spikes while help preveting temporary loss of control or runaway problems by preserving DCC waveform accuracy.
WHAT ARE THE SIGNS YOU MAY NEED A RC FILTER ON THE TRACK BUS?
1) Loss of train control
2) Runaway engines (Take off) :
3) Loss of decoder programming. 
4) Decoders blowing up.
Consider installing a snubber at the end of each cab bus