2008 Module 2 Calcs for Main line layout, Sort of signalling in branch line

[NJK]

Dear Members,
2008 Examination – Module 2 - Main line layout

Permitted speed for passenger trains – Main lines – 160 km/h
Permitted speed for passenger trains – Branch lines – 100 km/h

Headways at minimum signal spacing and at a speed of 140 km /h
Fast passenger train following fast passenger train – 2 minutes
Fast passenger train following stopping passenger train – 4 minutes
Station dwell times – 30 seconds

By using headway speed 140 km/h, we can find the sort of signalling in main line.
How to find the sort of signalling in branch line ?

Kindly clarify. Thanks in advance.

Regards,
NJK