I think after Quintishill we learnt that paying extra for loops is a better idea. I hope something good can be learnt from this accident.bi-directional working is also used for regulating purposes
Pilot working? That's really open to error and incredibly dangerous if the people are involved do not follow the rules.
Bi-Di's on the other hand are just a waste of space,mostly the only time you need them is during a system fault on the correct line,but that in turn has already knackered the Bi-Di's system as well nine times out of ten.