PF 2 (towards BSB) & 3 (towards LKO) of SLN are thru line & dnt need any caution now & always get green or thru starter (if train do hav stoppage)...
Simply, PF3/2 towards LKO/BSB dnt need any curve to negotiate & train can pick-up frm station itself!! If the train is non-stop towards LKO, thn it can pass with higher speed (provided chain dont get pulled), which nowhere is less thn 40-50 KMPH nwdays!!
PF1 & 4 (under construction) are loop ones!!