Ryan Bradley of GOOD pays a visit to ATSAC, which he says resembles the command centers one sees in movies and TV.
He writes, "ATSAC was created for two reasons. First, to adjust traffic signals in real time to respond to events that may cause congestion, like a car accident or a Lakers championship. Before ATSAC, the Department of Transportation had to send someone out into the field to adjust traffic signals. Now, these adjustments can be made throughout the city from this underground bunker next to City Hall, by those men watching those 16 screens, as thousands of cameras trained on thousands of intersections record the goings-on on the streets above."
The second goal of ATSAC, as Bradley points out, is to collect reams of data that can then be used to understand how traffic flows and where it can be improved.
Here's the the official page of ATSAC.