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Location Map ( geo)
Cameraicon.png View gallery (105)
From:  Cadnam (SU288134)
To:  Portsmouth (SU658045)
Distance:  28 miles (45.1 km)
Primary Destinations
Highway Authorities

National Highways

Traditional Counties


Route outline (key)
M27 Cadnam - Portsmouth
M27 Portsmouth - Chichester
Junction List
Junc Westbound Eastbound
1 A31; A337, B3079 Start of Road
2 A36, A326 A36, A326
3 M271 M271
Services symbol.gif Rownhams services
4 M3 M3
5 A335 A335
6 (A27) (A27)
7 A334 A334
8 A3024, A27 A3024, A27
9 A27 A27
Services symbol.gif Meon Valley services
10 A32 No Exit
11 A27, A32 A27, A32
12 No Exit A27, A3
12 M275 M275
12 Start of Road A3, A27
- A2030 A2030
- A3(M), A2030, B2177 A3(M), A2030, B2177
- A3023, B2149 A3023, B2149
- A259 A259
Services symbol.gif Emsworth services
- Proposed start of road A27, A259
For detailed information about this topic, see Motorway Database

The M27 is the South Coast Motorway, running from Cadnam in the west, bypassing Southampton and Fareham, to Portsmouth in the east. An extension to Chichester to the east was proposed, but eventually constructed as A27.

Being named South Coast Motorway, the M27 is often mistaken for the T37, which was referred to from the outset as the South Coast Trunk Route, leading to the myth that the M27 was intended to serve Folkestone and Honiton (or even further). Plans to upgrade parts of that trunk route to form a continuous high-standard road began in 1939, but only the section between Southampton and Chichester was ever intended to be replaced by a new road. As the plans for it progressed, in 1968 that new road was confirmed to be a motorway.

Catenary lighting was removed from the central reservation between J7 and J8 in an extensive refurbishment. Gantries were added here in 2006. The road originally opened with an entirely concrete surface, which was replaced in stages, and since the 2000s only J5-7 has been left. J3-4 and J11-12 were widened and refurbished in 2008; a project that saved an estimated 32 seconds from peak journey times. J4-11 was widened as a smart motorway in 2022.

Route History

Owing to the close spacing of the interchanges, the M27 has always been used heavily by short-distance traffic. However, it was built to address a growing problem of holiday traffic arriving from the radial routes at the weekend and clogging up the streets of Southampton and Fareham. The route of the road was described by engineers as "basically a series of connected loops", referring to it functioning as a series of bypasses.

The upgrade was confirmed in 1955. The western terminus was moved from Ower to Cadnam in 1968, to avoid the need for online upgrades on the A31.

In 1989, a study was held with a view to widening the road between J4 and J12. Work started in 2018 as part of the smart motorways scheme and in 2022 the section between J4 (M3 interchange) and J11 (Fareham) was widened mostly to four lanes. [1] This was reduced considerably from the previous plans, which would have seen 5 lanes provided between J4 and J5. A National Highways study concluded that there would be "significant benefits" and "significant benefit in congestion and accident relief" to building a full upgrade between J4 and J12, but they decided not to go ahead with it.

Future works are expected at J10 to create an access for Buckland Developments to build their new town. It is currently anticipated that construction would begin in 2023. More works are also needed to complete the resurfacing of J5-7, and to provide the suitable number of emergency refuge areas.

Stoneham Missing Link

The section between J4 and J7 was the last to open, and it was dubbed the 'Missing Link' because the delay prevented the road from effectively bypassing Southampton.

The cause of the delay was that the chosen route had J5 south of its present site, taking the motorway through Southampton's Ford factory. The factory employed 3,000 people, and when objections were raised it was decided to avoid them by choosing a new route, running closer to Southampton Airport, and then created a slight curve to the south to lessen the bend onto the diversion. This instead crossed a crematorium and memorial garden.

The slip roads at J4 and J7 were flared with space left for its completion.

The road opened with the unusual distinction of having a hedge instead of a central barrier. This was soon removed as it was too much work to maintain. An emergency crossover was installed, with great disruption, in 2013 (this was removed in 2018, having gone unused).

West End

The original proposal for the new road had it run north of Hedge End and west of Botley. Before the public inquiry it was changed to run west of Hedge End (past West End), as that way it would pick up more Southampton commuter traffic - now a common source of congestion. Had this happened, the current A3024 J8 spur would have been a lot longer, and called the Windhover Link.

One advantage of this route was that it ensures the crossing of the River Hamble was by the existing road and rail bridges, rather than disturbing the area further upstream. A straight design matching the existing bridge height was chosen to further reduce the visual impact.

Part of this section opened with catenary lighting. It had gantries installed, with great disruption, in 2005 (these were removed in 2018).


A long petition against the road came from residents of Burridge (north of J9). It had been suggested the road would dissect the village, but the chosen plan routed it as far away from the village as was possible.

Fareham and Portsmouth Harbour

By the time construction had already started on what should have become part of the M27 on the Havant Bypass, there were still several possible routes for it to take at Fareham: the chosen route, running north of the town and then south of the ridge of Portsdown Hill; the authority's favoured route, bypassing Titchfield and Stubbington, running south of Hoeford and then bridging across to Horsea Island (close to J12); or a combination of the two, crossing over in what would have been a gap in development west of Portchester.

The route south of Fareham was thought to offer more traffic improvements, but the section along the mud flats past Portchester Castle was unpopular despite assurances the close routing of the road could increase tourism. Additional work would have been required on the A333 at Wickham and Southwick, which wouldn't benefit from this route. In the end, the higher costs, damage to the shipping industry and engineering difficulties associated with the route meant the northern option was hastily built, and local attention then turned to whether it was still too close to Fareham.

The route through Paulsgrove was then protected for the final few years before construction started, while houses were built around it.

Despite the southern route offering relief to the A32, it was suggested this didn't justify the costs as the road would still have needed upgrading, with one inspector in 1962 recommending a D3 improvement and a bridge to Portsmouth.

In May 2022, a Stubbington Bypass opened, compensating for the motorway not relieving the village.


For detailed information about this section, see Pathetic Motorways Unfinished: M27 Portsmouth-Chichester

Throughout construction it was assumed the motorway would reach Chichester, where the bypass may have been upgraded. While the road between Havant and Chichester was eventually built as D2 A27, the road between Portsmouth and Havant was partly upgraded to D4M in preparation.

At Chichester, one proposal, which was second to the chosen, cheaper layout, considered extending the M27 north of Chichester, with a spur to the Fishbourne Roundabout, terminating near the Portfield Roundabout.

300 objections were received to the preferred route in 1972.

There is some confusion around the eastern terminus of the M27. What's now the A27 around Farlington was built in the 1960s as an isolated dual carriageway with flat roundabouts on it. The M27 was eventually connected to it, but changing the old road to a motorway would have come with a cost and there was little benefit to converting the existing road to motorway until the planned motorway to Chichester was built, which ultimately never happened as a motorway.

There are plenty of other theories floating around. One, that the gap in the hard shoulder over the railway bridge was a deal-breaker, may have been important to those involved at the time, but it's ultimately academic because the nearby M275, built at a similar time, has no hard shoulders at all. Another argument, which was even used by the Highways Agency, is that the A27 can't be made a motorway without accommodating non-motorway traffic. This is historically nonsense, as the A27 didn't exist there until the 1960s and its old route is still available, but now more than 60 years have passed and it may pose more of a legal hurdle.

Opening Dates

For detailed information about this section, see Motorway Database: M27 Timeline


see M27/Named Junctions page


Rownhams services

Rownhams service station - Geograph - 99075.jpg
Main Article: Rownhams services

Rownhams Services is a relatively small MSA located between the M271 and M3 interchanges. It is operated by RoadChef.

Meon Valley services

Main Article: Meon Valley services

Meon Valley was a proposed MSA located just to the east of junction 9, whose sliproads are constructed as access to the services, including the extremely long westbound exit. The sliproads were ultimately removed as part of the J4-J11 smart motorway scheme in 2022.

Traffic Data


Link 2002 AADF 2006 AADF 2010 AADF 2014 AADF
J1 45139 49444 45810 49461
J1-2 73296 79893 77179 75636
J2-3 98472 94602 108718 107081
J3-4 116208 120546 121807 119980
J4W-M3 50361 55474 55360 58566
J4 58247 67581 59480 68033
J4E-M3 24063 46238 55760 47161
J4A-5 99315 108081 111702 90429
J5-7 118955 130220 130499 135409
J7-8 114112 115398 118342 109723
J8-9 104311 113338 110548 112095
J9-10 92178 97168 94243 92562
J10-11 101516 112934 105075 113894
J11-12 115349 125316 121337 121083


National Highways

Smart Motorway Scheme

J10 improvements - Welborne Garden Village

Pathetic Motorways

Motorway Services Online

Related Pictures
View gallery (105)
Rownhams - Coppermine - 21390.jpgAbnormal load at Rownhams services - Coppermine - 17543.jpgM27 junction 4 - Geograph - 1294943.jpgJ10 Redesign.pngA36(M) - Coppermine - 4391.jpg
Other nearby roads
NCN2 • NCN23 • NCN236 • NCN288 • A27 • A33 • A35 • A36 • A36(M) • A326 • A334 • A335 • A336 • A3024 • A3025 • A3035 • A3057 • A3067 • A3120 • B3033 • B3035 • B3036 • B3038 • B3039 • B3040 (Central Southampton) • B3040 (Southampton Common - Bitterne) • B3041 (Southampton) • B3042 (Hampshire) • B3053 • B3057 (Southampton) • B3380 (Southampton) • B3397 • C20 (Southampton) • C68 (Southampton) • C69 (Southampton) • C74 (Southampton) • C351 (Southampton) • C500 (Southampton) • C501 (Southampton) • C502 (Southampton) • C503 (Southampton) • C504 (Southampton) • C505 (Southampton) • C506 (Southampton) • E1 (Old System) • E05 • M3 • M270 • M271 • M272 • T7 (Britain) • T37 (Britain) • T39 (Britain) • Townhill Link Motorway
NCN236 • A27 • A32 • B3385 • T37 (Britain)
NCN2 • NCN288 • A27 • A259 • A285 • A286 • A294 • A2024 • B2143 (Worthing - Chichester) • B2144 • B2145 • B2166 • B2178 • B2179 • B2201 • C3 (West Sussex) • C5 (West Sussex) • T37 (Britain)
Motorways in Great Britain
Current MotorwaysM1 • M2 • M3 • M4 • M5 • M6 • M6 Toll • M8 • M9 • M11 • M18 • M20 • M23 • M25 • M26 • M27 • M32 • M40 • M42 • M45 • M48 • M49 • M50 • M53 • M54 • M55 • M56 • M57 • M58 • M60 • M61 • M62 • M65 • M66 • M67 • M69 • M73 • M74 • M77 • M80 • M90 • M180 • M181 • M271 • M275 • M602 • M606 • M621 • M876 • M898
A1(M) • A3(M) • A8(M) • A14(M) • A38(M) • A48(M) • A57(M) • A58(M) • A64(M) • A66(M) • A74(M) • A92(M) • A167(M) • A168(M) • A194(M) • A195(M) • A308(M) • A329(M) • A404(M) • A601(M) • A627(M) • A635(M) • A666(M) • A823(M) • A1058(M) • A1077(M)
Motorway Spurs • (M4 Heathrow Spur • M25 T5 Spur • Walton Summit M'way)
Former MotorwaysM10 • M15 • M16 • M30 • M41 • M52 • M62 • M63 • M64 • M65 • M68 • M85 • M110 • M111 • M270 • M274 • M531 • M600
A2(M) • A4(M) • A5(M) • A8(M) • A11(M) • A18(M) • A20(M) • A21(M) • A23(M) • A36(M) • A40(M) (Central London) • A40(M) (Buckinghamshire) • A41(M) • A46(M) • A48(M) (Morriston) • A48(M) (Port Talbot) • A65(M) • A102(M) (North) • A102(M) (South) • A423(M) • A446(M) • A604(M) • A638(M) • A696(M) • A1231(M) • A6127(M) • A6138(M) • A6144(M)
Unbuilt MotorwaysM4 Toll • M12 (Woodford - Brentford) • M12 (Woodford - Maplin) • M12 (Brentwood - -Chelmsford) • M13 • M17 • M19 • M31 • M58 • M59 • M60 • M62 RR • M64 • M81 • M82 • M83 • M100 • M272 • M601 • M650
A2(M) • A6(M) (West) • A6(M) (East) • A14(M) • A48(M) • A59(M) • A61(M) • A556(M) • A695(M)
A Ring • Bilston Link • Belmont Link • B-W M'way • CME Bypass • CMW • Central Spine • Chippenham Spur • Coventry N-S M'way • Cublington Airport M'way • Denham Spur • Derby Urban M'way • Droitwich-Leicester M'way • East Coast M'way • EXR • East Kilbride M'way • E-W Underground M'way • Eastern M'way • Euroroute • Friars Goose Xing • Furness Link • Glasgow IRR • GM Western Relief Road • Hamilton-Cumbernauld M'way • Hook Road • Johnstone M'way • Kendal Link • Liverpool Inner M'way • LOX M'way • Malvern Radial • Manchester IRR • Morecambe Link • NE Urban M'way • NXR • N&W M'way • Paisley-Hamilton M'way • POLO • Princess P'way M'way • Reading Urban M'way • Ringway 2 • Sheffield Spur • S Bristol Spur • SCRPDR • SXR • Stirling Corner Link • Strensham-Solihill M'way • Strensham-Solihill M'way • TGAAR • Townhill Link • Trafford Park M'way • Warndon Radial • Watford Urban M'Way • Western Orbital • Weston Spur

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