RE: Custom Built R/C Trophy Truck - Project Mammuth
You shouldn't really run it unless you have fitted a killswitch failsafe. This will cut the motor in any of the following scenarios:-
Car goes out of range
Transmitter fails
Receiver fails (eg no signal for whatever reason)
Servo fails (you flick a switch on the Tx to kill the motor)
Power stops reaching the receiver (could be flat battery, bad connection, or even broken in an impact)
You simply turn off the Tx momentarily
Added bonus is that the motor will not start unless the radio (tx AND Rx) are both on and working - a good security feature no chance of an accidental start...
these things are so cheap you really shouldn't avoid one for a second.