Two main roads will be open again after tomorrow following weeks of work.
The A6 Desborough Bypass is set to re-open at midnight on Sunday (September 3) after a seven-month closure, and a section of Northampton Road in Kettering will also re-open from 4am on Monday (September 4).
The A6 has been closed since January after a routine inspection found faults under the carriageway near the River Ise bridge.
Further inspections found faults over the railway bridge and the road has been closed since, causing diversions and misery to commuters.
Northants Highways head of operations Leon Jolly said: “The process we’ve been using has been finding the voids and giving them structural integrity.
“I’ve not seen anything like this for 15 years, it’s rare but it does happen.
“While we’ve been doing this we’ve been doing a lot of works to make sure we are not coming back here.
“I would love to make promises but we have done everything we can.”
The total cost of the whole project is unknown at this stage, but the funds have come from the county council’s budget.
The county council is in discussions with the Department for Transport to see what funding is available for the work.
The section of Northampton Road in Kettering between Lake Avenue and the double roundabout has been closed for the entire school holiday period.
The continuous road closure took place for major work on the railway bridge as part of the electrification of the line between Kettering and Corby.
The work will strengthen the bridge – to allow more trains to use it – by repairing brickwork, installing tie bars and pattress plates and strengthening the spandrel wall.
Network Rail says it carried out the work during the school holidays to minimise disruption.