Improvement works to the A12 between junction 19 (north of Chelmsford) and junction 25 (Marks Tey, where the A120 approaches from Braintree) to provide three lanes in each direction for the whole of this length, a distance of 25 km (15 miles). At present this part of the A12 is a grade-separated dual carriageway with two lanes in each direction. Short, isolated sections have a third lane between junctions in a small number of places.
The scheme will involve widening the existing dual carriageway to provide an additional lane for most or all of the distance. Some design options involve a new offline bypass of the existing road between Witham and Kelvedon, or between Kelvedon and Marks Tey, or both.
The official name of this scheme is A12 Chelmsford-A120 Widening but is listed here under the name "Chelmsford-Marks Tey" to avoid giving the false impression that the scheme involves widening the A120.
The route between junctions 23 and 25 has been reconsulted on. This is because new developments around Marks Tey may impact on the proposed route. If the developments do not go ahead, the previous routes are still feasible.
A preferred route has been announced for junctions 19-23, including an offline bypass at Rivenhall End.
With thanks to Sam West for information on this page.