If your Monday plans take you west from Southampton towards the New Forest, Dorset or the A31, a few minutes of preparation this morning could prevent a frustrating late-evening surprise. National Highways lists an overnight closure of the M27 westbound from junction 1 at Cadnam to the A31 at Upper Canterton, beginning tonight, Monday 10 August, and continuing through Friday 14 August. The published closure window is 9pm to 6am.
What is changing tonight
The closure affects the westbound route where the M27 becomes the A31. Drivers approaching Cadnam after 9pm should expect to leave the motorway and follow a signed diversion rather than continue directly towards Ringwood. National Highways says the diversion begins at Cadnam Interchange, uses the A31 and A336, then continues by the A326 and A35. It later runs through Gosport Lane and Chapel Lane, returns to the A35, then uses the A3060 and A338 before rejoining the A31 at Ashley Heath Roundabout.
That is a longer and more complex route than the normal westbound run. Local junctions may also feel busier, particularly around Totton, Christchurch and Ashley Heath. Do not rely on a satnav shortcut through unfamiliar residential roads. Follow the official diversion signs, keep your map app updated and allow a sensible extra margin.
A simple Monday morning plan
If you expect to travel this evening, check the National Highways daily closures page again before leaving because planned works can change at short notice. Save your destination before you move, charge your phone and tell anyone waiting for you that the journey may take longer. If you can travel before the 9pm closure starts, leave enough time for ordinary summer traffic rather than aiming to pass Cadnam at the last minute.
For drivers starting beyond Southampton, note one or two safe stopping places before setting off. A planned service-area break is better than trying to make route decisions on the move. If traffic is unexpectedly slow, stay patient, keep a safe following distance and let the signed route guide you back to the A31.
Give the car a five-minute readiness check
Before an evening motorway trip, check fuel or battery range, tyres, exterior lights, washer fluid and the windscreen. Make sure your breakdown provider's details and policy number are accessible. Put water, essential medication and a charging cable where you can reach them without unpacking the boot. A torch is useful after dark, but it should be secured when the vehicle is moving.
Keep a high-visibility vest inside the passenger compartment so you can put it on before leaving the vehicle if it is safe to do so. A warning triangle belongs in a prepared roadside kit, but never place one on a motorway. If your vehicle develops a problem, use a safe refuge or leave at the next junction when possible; on a live motorway follow official breakdown guidance and contact the emergency services if anyone is in immediate danger.
Pack for preparation, not alarm
The JUFO 3-in-1 Roadside Breakdown Kit (£17.95) brings together a high-visibility vest, warning triangle and compact 2-in-1 window breaker with seatbelt cutter. Store the escape tool securely within reach of the driver rather than loose in the boot, and keep the vest accessible before every journey. The kit is a practical addition to your existing breakdown cover, torch, power bank and drinking water; it does not replace professional help.
Before the 9pm changeover
Take one final live-traffic look shortly before departure. If the closure is confirmed, build the diversion into your arrival estimate, use the signed route and avoid rushing to “beat” the works. If the closure is postponed, continue to drive to the conditions and retain the same readiness checks. The useful habit is not memorising every road name; it is checking the official source, preparing the car and making calm decisions before the journey begins.
Official source: National Highways — South East maintenance schemes. Details checked on 10 August 2026; closures may change at short notice.
