And if two hundred thousand people are going to file through an illuminated arcade, there'll be an orderly progression to deliver them there, which explains our letter S with the extra loop.
Getting that number of people there means the streets have been blocked off to traffic, which in turn creates issues with people who want to cross one of the streets. An opportunist gatecrasher would probably rate one of these crossing points as a place to jump the queue and join the flow, but each crossing point had a wall of uniformed police on either side of the pedestrian flow, which could be halted when there were enough crossers to justify the disruption.
At this point a placard was carried into the middle of the flow, the uniforms presumably moved across the flow, possibly moving the barricades, the crossers crossed, and after a minute or two things were moved back and the progression towards the display resumed.
If this all seems a tad too regimented and orderly, as you approach the actual display there are any number of instructions from uniformed officers carrying megaphones, exhorting the pedestrians to keep moving, which I suppose has to be said. You're not, however, going to get a decent photo, or a series of decent photos, while you're moving, so everyone stops.