What happens outside my window while I am sleeping

I was awoken suddenly the other night when my roommate dropped a wine bottle on the wood floor. Startled, I walked into the living room to see what the clatter was about. Going back to bed, I noticed flashing outside the curtains, and I peeked out to see this. I have no idea what time it was, but judging by my discombobulation, it was rather late. It makes sense that construction would go on in the middle of the night, considering the traffic flow of the average day. I live on the fourth floor of my apartment building (called Wing Tak Mansion, by the way) and I look out over the Canal Road flyover, so called because once upon a time, the roadway used to be an actual canal bringing water down from the mountain above. It was neat to observe this little moment, and a bit strange, because the world seemed completely different by (late) night.