Improvements to the highways network in Bury St Edmunds to enable it to cope with future development could cost about £10million.

St Edmundsbury Borough Council and Suffolk County Council commissioned consultants to assess 11 key junctions in and around the town that are likely to be under pressure as a result of the proposals included in the draft blueprint for growth in the area up to 2031.

Known as Vision 2031, it includes 900 homes between the Howard Estate and Fornham All Saints, 500 homes for Moreton Hall, 1,250 between Bury and Great Barton and 1,250 to the south-east of the town and 450 to the west of the town.

The infrastructure study produced by AECOM looked at four junctions of the A14, as well as seven roundabouts. The roundabouts are: Newmarket Road/Westley Road; Compiegne Way/Tayfen Road; Parkway/Risbygate; Parkway/Westgate; Rougham Road/Rougham Hill; Southgate Green; and Cullum Road/Nowton Road/Wilks Road.

A letter from Suffolk County Council to the borough council said: “At this time the county council’s estimate is that the cost to deliver the indicative improvements in the (consultants’) report, excluding A14 junction 45, would be in the order of £10million.”

Regarding the roundabouts, suggestions include keeping the roundabout or installing traffic lights. The consultants were also asked to look at ways to improve pedestrian and cycling facilities.

The consultants’ report said: “At the town junctions, the achievement of better facilities for pedestrians and cyclists comes at the expense of a reduction in the capacity available for motor vehicle traffic; however these facilities are required to support sustainable transport options to reduce traffic demand in the future.”

The letter from the county council said, from the current information available, there appeared to be “deliverable and affordable solutions” to mitigate the impact of the key strategic development sites. “However, it is not reasonable to assume that these improvements will result in nil detriment to the highway network within Bury St Edmunds.”

Green Party member Mark Ereira, county councillor for Bury’s Tower division and who is keen to see proposals coming forward around sustainable transport, said he had said all along if the borough agreed to such a high number of homes “this is the implications”.

Ian Poole, planning policy manager at the borough council, said the number of the homes for the five key sites, mentioned above, had previously been agreed as part of a planning framework called the Core Strategy.

A borough council spokeswoman said: “Part of the cost of development is funding infrastructure and this is a factor in assessing a project’s viability.” Developers would be expected to pay as much as possible towards infrastructure improvements, she added.

People have the chance to comment on the infrastructure delivery plan for Bury as part of public consultation on Vision 2031 from June to August.

An independent planning inspector will make the final decision.