The main construction work to repair the A6 Desborough bypass on the carriageway leading on to the railway bridge will start on Monday (July 3).
The first steps will be to set up the site compound and move all the required machinery and equipment into the location.
The county council says the works remains on target to be completed by the end of August.
A county council spokesman said: “We would firstly like to extend a huge thank you to all road users and businesses in the local communities for their patience and apologise for the inconvenience this has caused.
“Over the months, work has continued between our contractors and all associated parties to develop the best programme of repairs.
“Planning has required significant collaboration and co-ordination as we are working in a location alongside Midland Mainline who have worked with us to develop the best way to proceed safely and efficiently.
“The application for permission to work alongside the rail line was submitted to Network Rail and this process took time to agree and approve design solutions to minimise the impact to rail users.
“Collaborative work continues with Network Rail and all associated parties, including specialist contractors, and a repair solution has been agreed by all.
“We worked to amend the design of the repairs to ensure all licences were agreed following procedure and that everyone was happy with the way forward.
“This has not delayed progress and our main aim has always been to carry out the necessary repairs and reopen the A6.”
This construction stage of the project requires four specialist contractors who will be working seven days a week and weekends where possible due to rail traffic.
The main construction works will take place from 7am to 7pm every day.
Overnight working is not cost-effective due to the solution being used and the rail line.
The spokesman added: “Northamptonshire County Council are committed to opening the A6 and funding is available for the repairs.
“We are still in discussion and seeking advice regarding options to recover the full cost of all of the work undertaken to date.
“We have been working with our supply chain who have been on site, while the road is closed, to carry out works not associated with the emergency repairs.
“We have been taking advantage of the closure renewing road markings, road studs and signage.
“We will also be mowing, carrying out tree clearance, safety barrier inspections and barrier upgrades.
“We realise traffic volume has increased on the local network.
“Once the A6 reopens we will inspect all local routes and ensure road surfaces, where affected, are repaired and brought up to standard required.
“We have continued to monitor and repair safety defects on local roads during the A6 emergency closure.”
The main diversion route via the A14, the A43, A6003 and the A427 is still in place.