Sewer replacement works in Baxenden are set to last up to a month.
Temporary traffic lights have been installed on Manchester Road to allow the works by United Utilities to be carried out.
The scheme involves around a 100m stretch of road from Alliance Street to near Holland’s Pies.
A United Utilities spokesperson said: “It’s quite a complex job as there are quite a few other utility services on the road so we have got to go carefully. It is expected to take four weeks.”