The A12 southbound shuts overnight between junctions 25 and 23 from 10 August to 12 September, with the diversion coming down the A131 into Boreham.

Three things are shaping how traffic moves around Chelmsford this year, and only one of them is a set of cones. There is a run of overnight A12 closures that puts diverted traffic on local roads until October, a bridge in the middle of the city that has been down to traffic lights for more than a year, and a rebuilt Army and Navy junction that has slipped to the end of the decade. This page sets out what is happening, with the dates, and where to check on the day.

A12 overnight closures: 10 August to 12 September

National Highways is resurfacing the A12 and refreshing its markings between Chelmsford and Colchester. The work covers junction 20b (Hatfield Peverel South) to junction 22 (Witham North) and junction 24 (Kelvedon North) to junction 25 (Marks Tey), and it runs from 11 May to October 2026, with the main closures having begun on 13 July.

Closures are weeknights only, between 9pm and 5am, weather permitting. They come in three stages (National Highways):

A12 Chelmsford to Colchester maintenance, closure stages 2026
DatesWhat closes
13 July to 1 AugustA12 northbound, junction 19 to junction 22 (finished)
10 August to 12 SeptemberA12 southbound, junction 25 to junction 23
14 September to 10 OctoberA12 northbound, junction 19 to junction 25

Why this lands on Chelmsford

The stretch being closed is east of the city, but the diversion is not.

Southbound traffic coming down from Suffolk and Colchester is sent off the A12 at junction 25 (Marks Tey), west along the A120 past Braintree, then south down the A131 to rejoin the A12 at junction 19, the Boreham Interchange. Northbound diversions run the same route in reverse, leaving at junction 19 and rejoining at junction 25.

That means the practical effect for Chelmsford drivers is a spell of unfamiliar heavy traffic on the A131 and around Boreham between 9pm and 5am on weeknights, not roadworks on your own street.

The A12 overnight diversion route around the Chelmsford to Colchester works Schematic diagram of the A12 between junction 19 at Boreham, Chelmsford, and junction 25 at Marks Tey. The section between junction 25 and junction 23 is closed southbound overnight from 10 August to 12 September 2026. The signed diversion leaves the A12 at junction 25, runs west along the A120 past Braintree, then south down the A131 to rejoin the A12 at junction 19 Boreham Interchange, on the Chelmsford edge of the network. The closure is east of Chelmsford. The diversion comes back through it. Signed overnight diversion, A12 southbound closure junctions 25 to 23, weeknights 9pm to 5am, 10 August to 12 September 2026. A120 west past Braintree, then A131 south: the signed overnight diversion A12 open A12 southbound closed overnight, J25 to J23 J19 BorehamChelmsford J20bHatfield Peverel J22Witham J23Kelvedon South J24Kelvedon North J25 Marks Teyfor Colchester
Overnight only, weeknights, 9pm to 5am. Dates and stages can change at short notice: National Highways publishes a daily closure report.

And the A12 widening is not coming

For years the answer to A12 congestion around Chelmsford was the junction 19 to junction 25 widening scheme: two lanes to three, junctions 20a, 20b and 23 removed, two bypasses, roughly £1.2 billion. It received development consent on 12 January 2024.

It was cancelled. National Highways’ own page for the scheme now reads: “Following the conclusion of the Spending Review, the Government has taken the decision to cancel the A12 Chelmsford to A120 scheme,” in an update dated 1 August 2025 (National Highways).

That cancellation is not just a road story. It is one of the four reasons Chelmsford City Council had to reopen its Local Plan and find extra housing sites, because the widening was the infrastructure several strategic sites were counting on. The detail is on our Chelmsford planning news page.

What survives is smaller. A first phase of improvements at junction 19 Boreham Interchange, packaged with a new roundabout serving Beaulieu Park station on the A131, was approved in principle by National Highways and Essex County Council at the city council’s Planning Committee on 15 December 2025. Homes England has agreed in principle to put £12 million into it through a change to the existing Chelmsford Housing Infrastructure Fund award. The council expected to confirm the full funding package in spring or summer 2026, “with works to commence the following year” (Chelmsford Policy Board, 19 March 2026).

London Road Bridge: still on traffic lights

Closer in, the longest-running restriction in the city is on New London Road. Essex Highways installed temporary two-way traffic lights on 24 June 2025 as a precaution after defects were found in the cast iron structure of London Road Bridge. Priority goes to vehicles travelling from Parkway towards Bellmead, to hold down the queue.

The Park and Ride bus stop on New London Road, in front of Grosvenor House opposite the Job Centre, is suspended while the lights are in place. Walking over the bridge and use of the river beneath it are unaffected.

More than a year on, the council has still published no repair date and no reopening date: it is investigating the defects and assessing repair options, and says further information will follow (Essex Highways). If you plan a route through the south of the city centre at peak times, plan it as though those lights are permanent, because for now they effectively are.

Army and Navy: rebuilt junction, but not until 2028

The Army and Navy is the junction everyone in Chelmsford has an opinion about. The scheme to fix it, the Army and Navy Sustainable Transport Package, is real, funded and consented. It is also years away.

What it will build:

  • A hamburger roundabout, with traffic running straight through the middle between Essex Yeomanry Way and Parkway and everything else going round. It was the option 60% of respondents preferred at the 2021 consultation.
  • About 350 extra spaces at Sandon Park and Ride.
  • A new northbound bus lane on Princes Road, and bus priority on Parkway in both directions.
  • Walking and cycling improvements on the junction and its approaches.

The cost is £81 million, of which the Department for Transport conditionally committed £68.75 million of Major Road Network funding in October 2023, with Essex County Council and Chelmsford City Council making up the rest. Planning permission came in November 2024 and the government confirmed the scheme could proceed in July 2025.

Then the timing: construction “is expected to start in 2028 and be completed in 2031,” subject to land acquisition and utility agreements (Essex Highways).

What that means for you. Nothing changes at the Army and Navy this year, next year, or the year after. If you have been holding off on a route change or a move because the junction is about to be fixed, it is not.

Park and ride, and the alternatives

Two park and ride sites keep a lot of cars out of the centre, and both are worth knowing about while the London Road Bridge lights are in.

Sandon Park and Ride, Maldon Road, Sandon, CM2 7RU, has 1,377 spaces, plus 34 disabled bays, 9 parent and child bays and 2 EV charging points. It runs Monday to Friday 06:30 to 20:00 and Saturday 07:00 to 19:30.

Chelmer Valley Park and Ride is at CM3 3PR, north of the city off the A130, and also runs a weekday minibus shuttle to Broomfield Hospital.

The Essex County Council park and ride tariff (Travel Essex):

  • Adult all day: £3.10, or £2.60 if bought between 12 and 3 Monday to Friday
  • Group, up to 2 adults and 3 children arriving in the same car: £5.20
  • Child under 19: £1.00
  • 12 for 11 flexi ticket: £34.10
  • Older person’s or blue concessionary pass: £1.60 all day
  • Short hop: £1.00
  • Park only, no bus: £3.60 a day, and Park and Pedal £3.60 a day if you ride in from the site

Two things people miss. From 1 to 31 August, children aged 5 to 15 travel free on the park and ride. And after the park and ride buses stop for the evening, your ticket stays valid on First’s service 31 at 20:10, 21:10, 22:15 and 23:10 and service 336 at 20:40, 21:40 and 22:40, Monday to Saturday, from the park and ride stops in Chelmsford.

A separate commercial operator, Central Connect, also runs a Sandon service under its own fares of £2.50 single and £5.00 all day, having taken the route on commercially on 6 March 2026 (Chelmsford Park and Ride). Check which bus you are boarding before you assume the price.

If you would rather leave the car at home entirely, the train into London is 29 minutes at its fastest, and Beaulieu Park station opened with 752 parking spaces on the north-east edge of the city in October 2025.

Bus gates, and the fines behind them

Three Chelmsford locations are enforced by camera for bus lane and bus gate contraventions: Channels Drive, Duke Street and Gunson Gate. Essex County Council publishes the traffic regulation order and photographs of the signed approaches for each one. Duke Street in particular catches drivers who follow a satnav through the middle of the city rather than round it. If you are new to Chelmsford, that is the single most likely way to pick up a penalty here.

Where to check on the day

More Chelmsford local information

Sources

Roadworks change at short notice, and overnight closures are weather dependent. Check the live maps above before you set off. Dates and prices read on 9 August 2026.