I should've been more specific.
1: "Pace down" was temporary, cruising speed on the left lane is 130Km/h or so and then decelerated to 60km/h as approaching the area and then resumed the original speed. "Temporary creeping" might be suitable. My first impression was speed trap.

2: The velocity should be 10-15km/h when I got flashed, right after that I glanced the signal in the rear view mirror shows yellow.