Initial works have been carried out as part of the multi-million pound improvements for the Wilby Way roundabout in Wellingborough.
The £3.2 million, six-month programme to widen part of the roundabout and approach roads, and install traffic signals, was announced by the Government last year.
The money for the improvements, which started earlier this month, comes from a national fund given to the Highways Agency to improve congestion across the country.
The first stage of the roadworks has now taken place, including temporary lighting being installed.
A spokesman for the Highways Agency said: “Work at the Wilby Way roundabout has been taking place to make conditions suitable for the next stage of the scheme.
“We have now put in place temporary lighting and subject to weather conditions, the permanent construction phase of the scheme is due to begin shortly.
“The work will involve widening the A45 eastbound entry and exit at Wilby Way roundabout and the A509 entry and exit.
“The route around the roundabout itself will also be widened.
“Other improvements will include resurfacing and new drainage, signs, signals and street lighting.”
Works will be carried out between Mondays and Saturdays, using narrow lanes between 6am and 8pm, together with overnight lane and road closures.
The work is scheduled to run for 21 weeks, subject to weather conditions.