Surveys on the 1970s-built bridge are needed to help engineers finalise designs for a replacement structure.
The new bridge is needed because the current one is now at the end of its life, said a spokesperson for Network Rail.
In addition, the current bridge is single track and the new bridge will be wide enough to accommodate two tracks as well as freight trains.
During the road closure, a clearly signposted diversion will be in place.
Access for pedestrians and cyclists will also remain open throughout the project’s duration.