interlocking system and few questions

[oxfordjack]

Hello,

I would like to ask the following few questions:

1) if the lnterlocking system is degraded, what system may be put in place to maintain operation of railway.
(my query: Is it maintained by manual?)

2) Explain some ways in which a lineside signalling system without automatic train protection can contribute to the prevention of derailment.
(my answer:
a: Can we add more signal lights avoiding from high speed.........
another I do not know

3) how ATP prevent derailment?
(My anwer:
a) Given Target speed can prevent overrun.
.........