The congestion is expected to remain for several weeks as the lights are scheduled to be in position until 21st October.
The lights are required to connect sewerage and surface water drainage for the new Butler Wall Homes estate.
Also in Chepstow, Welsh Water closed Bulwark corner yesterday afternoon due to a collapsed sewer pipe.
It is expected that the emergency road closure on the corner of Bulwark Road and Hardwick Hill will end later today and the road will re-open as normal.