The A12 at Darsham shuts on weeknights until 21 August and four stretches are down to 30mph for Sizewell C. Current closures, diversions and what lasts.

Almost every disruption on the roads between Woodbridge and Southwold now traces back to one project. Sizewell C is building a nuclear power station at Leiston, a link road across the fields to reach it, a bypass round two villages on the A12, two park and ride sites and a rail route, and the works are spread along thirty miles of the A12 and the lanes either side of it.

That makes the roadworks here different from most places. They are not a summer resurfacing programme that ends in September. The published closure list runs to Q3 2027 in places, and the A12 speed limits are in force for the duration.

Everything below was taken from the Sizewell C works tracker bulletin published on 7 August 2026 and checked on 9 August 2026.

What is shut, and where

The A12 north from Woodbridge, showing current works and speed limits Route diagram of the A12 from Woodbridge north to Darsham. Woodbridge and Melton are clear. Wickham Market has slip road and High Street night closures and junction signals. Marlesford has nightly traffic lights until 20 August and night closures from 19 September to 4 October. Little Glemham to Benhall is limited to 30mph. Friday Street has lane closures and signals until summer 2026 and a 30mph limit. Stratford St Andrew and Farnham are being bypassed by a new 1.8km road. Saxmundham is clear. Kelsale to Yoxford is 30mph. Darsham is 30mph and the A12 closes on weeknights from 10 to 21 August. Thirty miles of A12, and most of it is a Sizewell C worksite Position on 9 August 2026, from the Sizewell C works tracker bulletin of 7 August. Read north up the page, Woodbridge at the bottom. DarshamA12 closed weeknights 9pm to 6am, 10 to 21 August30mph past the park and ride roundabout Yoxford30mph from Kelsale to Yoxford, link road roundabout SaxmundhamNo A12 works listed BenhallNorthern end of the 30mph bypass-construction limit Friday StreetLane closures and signals until summer 2026, 30mphNew roundabout being built for the bypass Stratford St A. / Farnham1.8km two-village bypass under construction Little GlemhamSouthern end of the 30mph limit MarlesfordNightly traffic lights 7pm to 5am until 20 AugustA12 closed nights, 19 September to 4 October Wickham MarketJunction signals 10 to 14 August, High Street shutovernight 19 to 20 August Woodbridge and Melton sit south of all of this. Nothing on the A12 between Woodbridge and Wickham Market is currently listed as under works.
The two-village bypass at Farnham and Stratford St Andrew is the one piece of this that leaves something behind: the road stays once Sizewell C is finished.

On the A12 itself

  • Darsham: closed weeknights, 9pm to 6am, 10 to 21 August, for a new pedestrian crossing. Northbound diversion via the A1120, B1116, B1117 and A144; southbound via the B1387, B1125 and B1122. It closes again 7 to 18 September and 5 to 16 October, 8pm to 5am, with a much longer diversion that runs A12, A14, A140, A143 and back to the A12.
  • Marlesford: nightly traffic lights, 7pm to 5am, until 20 August. Then the A12 here closes from 8pm on 19 September to 5am on Sunday 4 October, with a diversion via the A1152, B1069 and A1094.
  • Wickham Market: the A12 slip roads are closed from 10pm on Friday 7 August to 5am on Monday 10 August. The off-slip diversion is a U-turn at the A12 and A1152 roundabout; the on-slip runs via the B1078, A1152 and A12.
  • Friday Street: varying traffic management including lane closures and traffic signals until summer 2026, while the new roundabout for the bypass is built.

30mph on four stretches of A12

These are not temporary night limits. They stay while the bypass, the link road and the park and ride sites are built:

  • Little Glemham to Benhall, for the two-village bypass.
  • Friday Street, for the roundabout.
  • Kelsale to Yoxford, for the link road and its roundabout.
  • Darsham, for the park and ride roundabout.

Away from the A12 there is also 30mph on the B1122, Lover’s Lane and Sizewell Gap, on Buckleswood Road and Westward Ho for the rail route, and on Eastbridge Road for the link road. The B1125 has 30mph and 50mph sections with speed cameras.

In Wickham Market

The B1438 High Street between Chapel Lane and Crown Lane closes from 7.30pm on Wednesday 19 August to 5am on Thursday 20 August, diverting via the B1438, A12 and B1078. Daytime traffic signals are in place at the B1078 and B1116 junction from 10 to 14 August.

In and around Leiston

This is the worst-affected town on the coast, and several of these run for months or years:

  • Abbey Road (B1122) is closed 24 hours a day at the Leiston level crossing, 27 July to 20 September. The eastern end of Westward Ho is also shut for about 80 metres from the Abbey Road junction. Pedestrian access is being maintained.
  • The Station Road level crossing closure has been extended to 20 September. It was due to reopen sooner; the operator says “a fragile utility pipe was found when the works began” and asked for up to three more weeks. The approved diversion routes stay in place.
  • Hawthorn Road: closed 10 August 2026 to 30 April 2027, diverting via Harrow Lane, Abbey Lane and the B1122.
  • Moat Road and George Road: closed 26 May to September 2026, same diversion.
  • Pretty Road: closed until Q3 2027 while an overbridge is built, same diversion.
  • The Common, off Lover’s Lane: 26 June to 21 August.
  • Ongoing traffic signals on Lover’s Lane and B1122 Abbey Road, and on Buckleswood Road at the rail crossing.
  • Weekend closures of the B1122 at Leiston are expected through September, October and November, and weeknight closures between Yoxford and Theberton through September and October.

The villages

  • Fordley Road, Middleton-cum-Fordley: closed 10 August 2026 until Q3 2027, diverting via Fordley Road, Town Farm Lane, the A12 and B1122.
  • Littlemoor Road: closed permanently since 19 November 2025.
  • Hill Farm Road, Farnham: fully closed since 12 January 2026, diverting via the A12, A1094 and Botany Farm Lane.
  • The Green level crossing, Knodishall: 5 August to 5 September 2026.
  • Willow Marsh Lane, Darsham: closed until summer 2026 for the northern park and ride, diverting via Walpole Road, the A144 and A12.
  • Marlesford local roads: Marlesford Road north closed 1 June to 14 August for about 130 metres; Bell Lane closed nights 9pm to 6am, 5 to 20 August; Ashe Road closed 27 July to 7 September for about 130 metres.

The two-village bypass, and why this keeps happening

The single largest piece of road building is a 1.8km bypass of the A12 around Farnham and Stratford St Andrew, two villages the trunk road currently runs straight through. It comes with a new roundabout at Friday Street. Unlike the haul roads and site accesses, this road stays once Sizewell C is finished, so the disruption at Friday Street and Little Glemham buys a permanent change to the route.

Until it opens, the A12 north of Wickham Market is a construction corridor with 30mph limits, and the diversion routes when it closes at night are long, because there is no parallel road of any size on this coast. The southbound Darsham diversion in September and October runs all the way round by the A14 and A140.

Checking before you set off

  • Suffolk County Council publishes live works on the Causeway one.network map, which is the authoritative list for the county: current and planned roadworks in Suffolk. The council notes that the A11, A12 and A14 trunk road sections are managed by National Highways, not by the county, so major-road incidents are handled separately.
  • Sizewell C publishes its own weekly bulletin of closures, diversions, abnormal load movements and rail works at the Sizewell C works tracker. It is updated more often than any other source for this stretch of coast, and it is where the dates above come from.
  • Dates on this page move. The Leiston level crossing closure has already been extended once, from late August to 20 September, and the works tracker is the place that will say so first.

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