I just started here after 35 years OTR so am still trying to figure out this LTL thing. Recently I was number 2 for an evening linehaul. Being low man on the totem pole this is understandable. I was told my start time was 915PM, the senior driver was 845PM.......all going to same location. My set was already hooked. Now I've been told I can punch in up to 7 minutes early, so at 908 I punch in & head out to the truck. The 845 driver was running late & came in as I was punching the clock. when I went to the truck he was starting his paperwork. I was fixing to leave when the FOS came running out & said I couldn't leave until after the senior guy left the yard. When I asked why All she said was "all hell would break loose" if I left before him because he had seniority. I sat there for about 5 minutes till he came out & left. No big deal, but I am curious as to what would have happened if I had left before him.