The reason is work was taking place underneath the carriageway, and could not have been carried out with traffic overhead.
Sunday's closure was to allow an inspection of the carriageway and the supporting steelwork. Work began at 02:00 in the morning. Our intention was to reopen the carriageway by 10:00; however, the inspection revealed damage which required immediate repairs. For this reason the closure was not uplifted until 12:30.
I appreciate how frustrating it is to be stuck in traffic, particularly when it's not clear why. However, I assure you that we do not close the carriageway lightly and this was essential maintenance.
Forth Road Bridge