PCM Failsafe
I run a Futaba PCM radio that has built in failsafe. But that only helps if someone jumps on your frequency. I watched as another persons car raced out of control while mine sat with the brakes on when he forgot to check the frequency board to see I was on it. A throttle return spring will not help for this. You need a failsafe. Or people to obey the rules.
But if you lose your battery or strip your throttle servor, nothing but a return spring will help.