Lower speed limits may be brought in along the A12 east of Ipswich when the 2,000-home Adastral Park development is built at Martlesham Heath.
Developers accept the housing will increase traffic levels, but believe proposed changes to roundabouts on the dual carriageway between Seven Hills, Nacton, and the A12/A1214 junction at Martlesham Heath will mean only “minor adverse” delays for motorists.
Expert analysis of the five roundabouts has shown there have been more than 100 accidents in the past five years with 82 people injured, but most were “rear end shunts” and safety on the main road is not an issue.
Brookbanks Consulting (BCL) was appointed by Carlyle Land Ltd and CEG to produce a Transport Assessment and Travel Plan for Adastral Park.
The company said while the A12 is 70mph for a large part of the stretch between Seven Hills and Martlesham, “through discussions with Suffolk County Council, the aspiration to reduce the speed limit has been identified”.
This is most likely to be on the stretch between the BT and Foxhall roundabouts, where there will be a new traffic light controlled access for the development, but could affect other parts, too.
Traffic predictions show vehicle numbers could increase by more than 10% – the threshold at which action is needed – at around 20 junctions in the wider area. On the A12 itself, this increase could be as high as 229% at peak times at some roundabout entrances.
BCL said: “The results demonstrate that the delivery of the development has the potential to increase flows in numerous locations.
“The increases are not unexpected, the delivery of the development will fundamentally increase traffic levels. However, an increase in traffic does not then necessarily relate to an increase in delay or congestion.”
The research indicated that the predicted levels do not exceed the theoretical highway capacity.
Other proposed road improvements include traffic lights at Seven Hills roundabout, and widening of approaches up to four lanes at some roundabouts.
The developers will also try to encourage new residents to turn away from the car – with bus services every 20 minutes by phase three of the house building, and a drive for more shared car use.
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