Section 1: Whiteparish - Portsmouth
Starting in the west, the A27 begins as a non-primary single carriageway at a traffic-light controlled cross-roads on the A36 and the entrance to Brickworth Quarry just outside the village of Whiteparish. The A27 is purely a local road passing through rural villages and has sections limited to 30, 40 and 50 mph until it gets to Romsey, where it makes a half-hearted attempt to bypass the town and instead ends up weaving all about the area including a multiplex with the A3090 (former A31). Nothing much happens until the A27 runs through leafy Chilworth, where it locks on to the A33 in the middle of the M27/M3 interchange. It then bears east and begins to follow the M27, which is of course the A27's bypass. It runs through the suburbs managing to land within a mile of just about every junction of the M27, without actually appearing at any of them (although it is signed at a few). Eventually leaving Southampton and crossing the Hamble, running in to Park Gate and the large Sedgensworth Roundabout. Here the road becomes dual carriageway as it by-passes a series of retail parks, up to the next roundabout.
Immediately after the next roundabout the road forks around a house and then heads downhill, bypassing Tichfield, and then back up again as it passes through the Tichfield Gyratory and begins to enter Fareham as a dual carriageway. After a short go at being single carriageway again, the road bypasses Fareham on what is probably the highest standard road encountered so far. We pick up the A32 at the Quay Street Roundabout where there is an interesting flyover eastbound which runs right next to the equally elevated railway line. There is then a TOTSO down a sliproad onto the Delme Roundabout as the next flyover leads to M27 J11.
Still a dual carriageway, the A27 runs through Portchester, before becoming single again. It then becomes dual to bypass the centre of Portchester, becoming single as it runs alongside Portsmouth Harbour. Then once again it becomes dual as it heads under the M27 and past several new developments, reaching a set of traffic lights on the site of a former roundabout at the top of the M27 J12 spur. The A27 goes straight here in order to stay alongside the motorway, but the former route of the road bears left as the realigned A3 towards Cosham. Staying dual, it flows freely on to another roundabout, this one beneath the M27 at the eastern part of J12. Here it heads up the sliproads where the A27 now takes over the main route as the M27 has ended.
Section 2: Portsmouth - Worthing
From here the road still has three spacious lanes and a hard shoulder, although this drops as it heads over a railway bridge, meaning that pedantically the motorway has to stop where it does. This is odd as the nearby M275 doesn't have hard shoulders, and thanks to recent roadworks the M27's up to here are intermittent. Today the Highways Agency claim that this bit won't become a motorway because there is no alternative route despite the Havant Road providing one.
This is the first time the road has become properly rural, and it's also the first time it has been a clearway. The A27 runs alongside the sea here (as Portsmouth is an island) on reclaimed land and then crosses the A2030 at the Farlington Roundabout. There is a service area here, another first, and the road gains a fourth lane. The hard shoulders are red here, showing just how often they get resurfaced. Next, as a series of gantries announce, the road splits, with two lanes heading off as the A3(M) as well as meeting the old road. With only two lanes left, the road passes under the other half of this large junction and loses its hard shoulders too. The road begins to bypass Havant, crossing the old road to the east of the town, which is now part of the A259, a road we follow for the remainder of our route, over 60 miles. Although the road is only two lanes wide, the M27 was planned to continue here along almost exactly the same route, but was scaled down to save costs. The road goes eight miles with absolutely nothing happening, and until recently it had a noisy concrete surface which made it feel like it went on forever.
Next up is the Chichester bypass which has six congested roundabouts and one signal-controlled crossroads all in three miles. The route of the bypass is quite circuitous too, leading to claims that it's actually quicker to drive through Chichester than by-pass it. There are plans to grade-separate and close off some of the junctions. After the final roundabout at Portfield it is then onto the Westhampnett bypass, a 1990s construction with a GSJ for the A285. Shortly after this there is another roundabout and the road has several side turnings. The next section has a sign stating "No Racing by Horse-Drawn Vehicles", suggesting that this may have once been an issue, and leaving one wondering whether such behaviour is OK elsewhere. The road is quite straight (hence the racing) with a couple of sweeping curves before reaching the A29 and the Fontwell Bypass where there are yet another two roundabouts while the road multiplexes with the A29. At both roundabouts the A27 TOTSOs, leaving the lesser, single-carriageway A29 looking like the more major route.
The road continues east, again with numerous side-turnings, until it becomes single carriageway to run through Arundel. Cue another two roundabouts this time for a multiplex with the A284, and a bridge over the River Arun between them. It's then over the railway line and up a hill to reach Crossbush and its notoriously incomplete GSJ. This is where the "real" Arundel Bypass was meant to come out. The road has been planned and cancelled countless times and the sort-of-signalised-roundabout is actually a dumbbell with a temporary extra embankment sitting on unused carriageway. It is so temporary in fact that it has needed much strengthening work since. The carriageway actually makes it to the bridge that carries one side of the junction, but traffic has been diverted to the sliproads by this point.
From here the road bypasses Crossbush and continues as a dual carriageway, sweeping up the hill at Hammerpot to one of the newest sections of the road, this being the junction with the A280 (and the ethereal A2700) at Patcham. This junction, the one with the A285 and the Brighton and Hove Bypass demonstrate the quality that was once planned for the entire trunk section of the A27. Next up is the most obviously unimproved section of the road, through Worthing.
Section 3: Worthing - Brighton
Things start to degrade as the road narrows to single-carriageway and a 40mph limit, with housing appearing on both sides. There are numerous side turnings and pedestrian crossings before a couple of tight bends around Durrington Cemetery to reach Offington Corner and the A24, which hasn't had the best time of getting into Worthing either. The A24 then multiplexes until the Grove Lodge Roundabout, which has a traffic-lights to go with it. Some of the older signage states A24(A27) belying the fact that had the planned Worthing bypass been built this section of road would have just been the A24. After Grove Lodge the road heads directly east, still going through the suburbs of northern Worthing before reaching two sets of traffic lights which serve a couple of retail complexes and the main eastern access to Worthing and its industrial estates. Here the Sompting bypass starts and it's back to NSL D2 for a bit.
Having been built in the 1930s then Sompting bypass now ends in the middle of Sompting at the Hill Barn Traffic Lights. The road then continues as a D2, but with a 40 limit, through modern Sompting and into North Lancing, a section of road which is again a long-ago built bypass. There is then a roundabout with the A2025 for access to both North and South Lancing before heading off towards Shoreham Airport, with NSL signs appearing once the final housing estates are passed.
Things once again improve as the road crosses a set of lights outside Shoreham Airport and then there is a spectacular 1970s interchange, the Adur Viaduct with the A283. This is no doubt the best bit of the road, as it passes under the impressive Mill Road bridge. Next starts the excellent Brighton and Hove Bypass where the road heads north of the city and begins an exciting roller-coaster ride across the downs. First comes the wonderful Alpine-style Southwick Hill Tunnel, which comes with the usual 'prohibited traffic' warnings (though you can walk over the top of it), before a dumbbell junction with the A293. The road sweeps down into a valley and then climbs steeply for a junction with the A2038 and Dyke Road, where a lane is gained for the run down to the junction with the A23. The A27 meets the A23 at junction, which while probably not the best, is still pretty good considering the geographic constraints. It's sort of an off-set dumbbell with a free-flowing slip or two.
Section 4: Brighton - Pevensey
Having lost the 3rd lane there is then a long drawn-out junction with some unclassified roads before new road meets old at the A270 by Stanmer Park, with 3 lanes again as the road passes Sussex and Brighton Universities and the Amex stadium, home of Brighton and Hove Albion. The 3rd lane is lost to the Falmer junction, which has two odd onslips squished in to the surrounding area. Despite being quite a small village the A27 manages to run right through the middle of Falmer, as a D2 in a cutting. A glance at aerial photography of the area would suggest that a large part of the village was destroyed at some point to make way for the A27 and the junction. The first sign that things are starting to degrade again is the signalised roundabout with the A277 to the west of Lewes. Lewes is bypassed to the south on what is a fairly good road, but then hits another roundabout which marks the end of dual A27. To the left is the A26 towards Uckfield.
From here it's one lane down the hill and two lanes up on the newest bit of the road. At Beddingham the level-crossing has been replaced by a railway bridge, but still isn't dual-carriageway. This section is also carrying the A26 before it heads south to Newhaven at the next roundabout. The A27 continues as a single-carriageway, first quite straight and then more twisting through a couple of villages and onto Polegate. Here the A27 turns left at a set of traffic lights with the A2270 and reaches a grand roundabout where the A22 comes in from the north and both roads head east on the Polegate bypass. This is another "half-built" road, with the original plan being for a link to avoid the traffic lights and possibly a GSJ instead of the roundabout. The road is D2 here until the next roundabout, where the A22 continues south to Eastbourne on the Golden Jubilee Way. East Sussex County Council managed to built The Golden Jubilee Way some time before the HA managed to finish the Polegate bypass so for a while it just looked like a big road to nowhere in particular.
The final stretch is on an S2, but grade-separated, bypass of Pevensey before the A27 ends at a roundabout with the A259, which takes over as the South Coast Trunk Road from there. While this may seem an odd place for a major trunk road to change number, and the A27 to end, this is due to the A27 originally ending in Brighton and then taking over parts of the A26 and the A274 in the 1950s.