The closures, which will run from 8pm to 6am, will let engineers carry out checks of the carriageway ahead of full resurfacing later this year.
The roads will be analysed to decide what resurfacing method will be used and if any other repairs or improvement works will need to be done at the same time.
Engineers will look at the existing construction of the road, identify the location and depth of underground services and test the existing drainage system.
North Somerset Council’s executive member with responsibility for highways, Cllr James Tonkin, said: “Our teams have been in touch with businesses and homes in both areas to make sure the overnight road closures cause as little disruption as possible.
“There will be a clearly signed diversion route, but, anyone who is planning to travel in the area during the work may want to check out our roadworks website to help them plan their journey.
“The nature of the testing work means the full closures are needed to keep our crews and the people who use the route safe.”
The investigation works will be done by Skanska, North Somerset Council’s contractor.
Real time information about roadworks, include diversion routes, is available online at www.n-somerset.gov.uk/roadworks