20 yrs otj, i never saw a "fire line"
That was a thing back in the 30's, 40's, 50's and 60's. At a multiple PD would keep people back out of the way, detour traffic, etc. so the members were not hampered in firefighting. You have to remember also, that the citizens back then were not like today where everything is an inconvenience and infringement on their liberty if you decide to establish a fire line.