There was a Cast service celebration (in essence a park buyout). Traffic for these things at DHS gets crazy, so attendees get assigned varying travel routes and parking locations. Because these are "public" roads, law enforcement provides two functions that Disney Security cannot. They can close certain intersection movements, for example not allowing left turns into the park entrance. They can also direct traffic. But at an intersection with a working traffic signal they don't typically stand in the middle of the street anymore, they plug in a remote control at the service panel and manipulate the signal. They probably had their patrol cars lit up to alert people that something different was happening and to pay attention. Think about the number of Cast Members that probably drive that road on autopilot every day.
You see cops setup traps at a number of places at WDW. Here are some of their favorites. Last 10 days of the month ramp up for quota time.
- Stop sign rollers at Vista Blvd and Live Oak Lane
- Seatbelts, headlights, etc at DTD parking lot entrances
- N Buena Vista Dr just past Saratoga, usually in the evening behind oak trees in median.
- Epcot Center Dr, often sitting in median
- World Dr between Epcot Center Dr and 192, usually late at night.
- Western Way, usually early morning or evening hiding behind the overpass.
- Center Dr, around the Contemporary
