A look at a satellite view shows the bridge pretty much empty - maybe 3 trucks. And no backup at the 'customs house' on the end - totally empty lanes. Maybe it was a holiday or the weekend; but still.

https://www.google.com/maps/search/kong-zhuhai-macau+bridge/...

Oh! The HK end is still under construction in the picture. So its old. The trucks are probably bringing supplies for construction.