Further work on the multi-million Rising Bridge roundabout scheme is due to take place in December - three months after it was due to have been completed.
New traffic lights are due to come into operation by the end of November, with resurfacing work planned for December.
Work is also taking place until Sunday, November 13 to improve safety and reduce delays at Rising Bridge roundabout, near Haslingden, requiring some lane closures and overnight road closures.
Highways England has admitted that the work has been ‘challenging to complete’, and pledged to learn lessons from the delays.
A spokeswoman said: “Our contractors encountered some unexpected ground conditions for the slope stabilisation part of the scheme and issues with stone and wet peat while installing the lighting columns. The only safe way to deal with this issue is to schedule some additional overnight closures may be required.
“The scheme has been challenging to complete, and we are discussing with the contractor the lessons that can be learned.”
She added that a representative from Highways England had met with the Huncoat Community Forum to discuss the delays.
She said: “We appreciate that residents have been very patient, so it was important to meet with them to explain what is involved, what it will mean for traffic in the area, and why it would not be safe to complete the work without closing the road.”
Highways England had previously advised that the £4.5million works, which began in March and were originally scheduled to end by August 31, had been forced to run into mid-September due to ‘unforeseen circumstances’, which included uncharted utility services, weather condition and road traffic collisions in the area.
It is installing new traffic lights, pedestrian crossings and cycle lanes - as well as resurfacing the roundabout - and aims to link villages, schools and businesses on either side of the A56.