A stretch of the A45 will now not re-open until November after wet and windy weather caused delays.
The westbound section of the busy trunk road, between Rushden and Wellingborough, closed in February so a railway bridge could be demolished and re-built so the line could be electrified.
Since it was closed a contraflow system has been in place in the eastbound carriageway with speed restrictions.
Network Rail originally said the A45 would fully re-open by October 16. But today (Monday), exactly one month before it was scheduled to open, they have announced it will now not fully re-open until early November.
Whilst work to upgrade the structure is in its final phase and will complete on schedule, poor weather conditions over key summer weekends hampered work on-site and caused the delay.
Gavin Crook, principal programme sponsor for Network Rail, said: “I would like to take this opportunity to apologise that the road will not fully re-open on Wednesday, October 16.
"Whilst we have been able to recover most of the time caused by the wet or windy conditions affecting key crane lifts, we have not been able to overcome the weather completely.
“I would like to reassure motorists, residents and businesses that we are working as hard as we can to fully re-open the road and we would like to thank them for their continued patience.”
The contraflow will be removed in early November. Network Rail is also advising those living in the area that there will be a small number of short-term single lane closures on the eastbound carriageway in November as work takes place to raise the height of the walls on the older bridge section.
The walls need to be raised to prevent people coming into contact with live electrical equipment below.
The delay is the latest in a line of extensions to road closures caused by the electrification works.
The Cottingham Road bridge project in Corby over-ran by two months last year.
Businesses on a Wellingborough industrial estate have been left in limbo after bridge closure that was supposed to last six months became - after a couple of U-turns - a closure lasting more than 18 months. They have since been denied compensation.
And earlier this month Network Rail announced works on the Station Road bridge, between Isham and Burton Latimer, are also behind schedule.
The bridge works are required in order to provide safe clearance from overhead line equipment as the route between Bedford, Wellingborough, Kettering and Corby is electrified.