Drivers are being asked to leave more time for their journeys while Lancashire County Council carries out vital work to a bridge on the A6 between Bilsborrow and Barton.
Engineers are installing safety barriers next to White Horse Railway Bridge which carries the A6 over the West Coast Mainline.
This is being done to prevent vehicles leaving the road and to meet standards requiring rail lines to be protected from traffic. The new barrier will also allow future works to replace the adjacent footbridge to go ahead.
Temporary traffic lights will be in place either side of the bridge to allow the work to be carried out safely from 9am to 4pm, Monday, June 30, to Friday, July 4.
Harald Nielsen, principal bridges engineer, said: “We’re working outside of peak hours and our schedule is to complete the job within five days to minimise disruption as much as possible but we sorry for the inconvenience this will cause.
“We need to install the barriers to prevent vehicles accidentally leaving the road and coming to rest on the railway.
“In future this will allow us to replace the adjacent aging footbridge with a stronger one which offers protection to a very important piece of rail infrastructure.
“We’re grateful for people’s patience while the traffic management is in place.”
The White Horse Rail Bridge is located between the junctions with the A6 of White Horse Lane and Jepps Lane.