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|---|---|---|---|---|
 M23 highlighted in blueShow interactive map _map.svg) Shown with UK motorway network Show UK motorways map | ||||
 The motorway crossing over theM25, 2014 | ||||
| Route information | ||||
| Maintained byNational Highways | ||||
| Length | 15.9 mi (25.6 km) | |||
| Existed | 1974–present | |||
| History | Opened: 1974 Completed: 1975 | |||
| Major junctions | ||||
| North end | Hooley | |||
| Major intersections |   J8 →M25 motorway   A23 | |||
| South end | Pease Pottage | |||
| Location | ||||
| Country | United Kingdom | |||
| Counties | Surrey,West Sussex | |||
| Primary destinations | London Croydon Gatwick Airport Crawley Brighton | |||
| Road network | ||||
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TheM23 is amotorway inEngland, running from the south ofHooley inSurrey toPease Pottage, connected to the south of the significant town ofCrawley inWest Sussex. Hooley is immediately south of theLondon Borough of Croydon. Both ends of the motorway form a de-merger from (and merger back into) theA23 which runs fromLondon toBrighton.
Its northernmost part amounts to a 2-mile (3.2 km) spur north of junction 7 of theM25 motorway (junction 8 of the M23) which has spur roads for all directions (is astack interchange) and intuitively would be numbered 1 – as a long, publicly opposed section further to the north was never built. During its 17 miles (27 km) length it runs without a serving junction for central parts ofRedhill, Surrey, as its next and busiest junction is forGatwick Airport and it concludes with three, widely spaced out, for Crawley which also serveHorsham andEast Grinstead. It cuts through the a gap in theNorth Downs and a slight gap in theGreensand Ridge, long mainly wooded hill ranges, locally part of theSurrey Hills National Landscape. For the airport to its west, junction 9, has no direct routes to the more rural east; however sweeping to the north-west point of the airport, the M23 Spur gives ready access toHorley,Charlwood and all the northernmost parts and associated out of town workplaces of Crawley.
To the south the A23 is a dualled trunk road so far as the city ofBrighton, whereas to the north it sees long single-carriageway urban parts, in the centre of Hooley, northCoulsdon, southPurley, and no traffic-prioritised continuations to reach Inner London, which was the original scheme behind the motorway.
The motorway was constructed between 1972 and 1975, at the same time as the southern section of the M25 fromGodstone toReigate (M25 junctions 6 to 8).[1] The current northern terminus at junction 7 runs along most of what would have been its own sliproads for a broad northern continuation. In so doing, these splayed roads split to offer access to the more urban road which the M23 bypasses, the A23, and a flyover above the splayed fledgling motorway still exists for the onward northern continuation which remains unused, between these briefly, but widely, splayed carriageways of the motorway.[2]
The cancellation of the unbuilt northern section from theM25 in towards Central London has resulted in the A23 carrying the majority of traffic through South London to the motorway. This is largely a single carriageway route, with many level junctions, traffic lights and awkward interchanges. It travels largely through residential areas and means south London reliance on the A22 (hence the Caterham Bypass), runningSSE, andA3/A3M running SW (southwest).
A new junction (J10a) was opened in 1997,[3] between J10 and J11, for access to the newCrawley neighbourhood ofMaidenbower.[4] It was financed as part of the development of Maidenbower by the construction consortium. It has only a northbound slip road, no southbound access.
The M23 was planned to relieve congestion on theA23 throughStreatham,Thornton Heath,Purley andCoulsdon in south London and was originally intended to terminate inStreatham Vale at a junction with the controversialLondon Ringways Plan'sRingway 2 (the intended replacement of theSouth Circular Road (A205)).[5]
In an earlier version of the Ringways Plan it would have continued into central London where it would have met theBalham Loop spur fromRingway 1 (the London Motorway Box) atTooting.[6] This was dropped in 1967 when the northern terminus was changed to Ringway 2. While a definite route had not been chosen at that time for the northern section, approval was met for the route south of theGreater London boundary at Hooley.[7]
By 1972 the southern section of Ringway 2 had been dropped from the plan,[8] with an alternative proposal that the M23 continue further into London to end on Ringway 1. This was immediately countered in the same year by theGLC, who announced they would not be building that Ringway,[7] which meant that had the M23 continued into inner London it would not have had the arteries required at its northern end to distribute traffic to the east and west. The plan was again scaled back to scrap any reaching toMitcham Common but which would see an unsuitable terminus on Croydon Road (A232).[7] and Minister for Transport "postponed indefinitely" the plan. By the late 1970s, this proposed northern corridor earmarked for significant demolition sawurban blight,[9] and while the proposals were finally dropped in the mid-1980s, pockets of land that had been acquired were not released by theDepartment for Transport until the mid-1990s.
The unbuilt six-junctions motorway north of Hooley was due to the refusal of the GLC to finance the project, understanding the ultimately decisive, large-scale opposition to the construction of London Ringways, any network of high speed roads within London.[7] However, the scale of the four-tier junction between the M23 and the M25, one of only threestack interchanges in the UK at the time, is indicative of the importance attached to the M23 at that time.
The motorway and its road continuations mirror its secondary importance to London in the original system of road numbering zones 1 to 4; the A23/M23 running due south from London, is as the original axes suggest, less arterial for London traffic than Central London's eight main routes the M1/A41, the A1 (as far in as Finchley), M11/A205, A2/M2, A3 and M3/A316, M4 and A40/M40. To these can be added, much expanded, three roads running far intoEssex which are at least doubled, just as they are deep into London.
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Between July 2018 and July 2020 works took place to upgrade the M23 between junctions 8 and 10 to anall-lane-running motorway. The upgrades took place mostly for more reliable journeys to Gatwick Airport and increase the overall capacity of the route. The upgrades include an all-lane-running motorway, 12 new emergency areas, a new concrete central barrier replacing the current steel one, new roadside sound barriers, variable speed limits and two new emergency access slip roads. Changes were also implemented on the M23 junction 9 spurs: the hard shoulder westbound now a running lane; and for 50 mph (80 km/h) speed limits in both directions.[10]
In January 2020 all smart motorway projects were put under review due to concerns about their safety, during this period no new smart motorways could open. The review was published on 12 March 2020 and required no immediate amendments to the design or construction, however new technology to detect static vehicles is required to be fitted within three years, and a review on spacing ofemergency refuge areas was to be carried out.[11]
The fourth lanes were opened to traffic on 2 April 2020 with a temporary 50 mph speed limit. Works ran into the late summer to install more equipment, followed by testing and commissioning, before the project could complete and run at thenational speed limit.[12]
Data fromdriver location signs are used to provide distance and carriageway identifier information.[13] Where a junction spans several hundred metres (yards) and start and end points are available, both are cited.[14]
| County | Location | mi | km | Junction | Destinations | Notes |
|---|---|---|---|---|---|---|
| Surrey | Merstham | 17.0 17.5 | 27.4 28.2 | 7[coord 1] | A23 -Croydon | Road continues as A23 to Croydon |
| 19.0 19.3 | 30.5 31.0 | 8 Merstham Interchange [coord 2] 51°15′51″N0°07′40″W / 51.26417°N 0.12789°W /51.26417; -0.12789 (Junction 8 of the M23) |  M25 -Heathrow,Watford,Dartford Crossing,Reigate | |||
| West Sussex | Horley | 26.5 26.8 | 42.7 43.1 | 9[coord 3] | A23 -Gatwick,Redhill | Terminus of spur towards Gatwick |
| Crawley | 28.5 28.6 | 45.8 46.1 | 10[coord 4] |  A264 -East Grinstead | ||
| 30.3 30.6 | 48.8 49.2 | 10a[coord 5] | B2036 -Crawley | No exit from M23 Northbound, no access to M23 Southbound | ||
| 33.1 33.4 | 53.3 53.8 | 11[coord 6] | Pease Pottage services | Road continues as A23 to Brighton | ||
| 1.000 mi = 1.609 km; 1.000 km = 0.621 mi | ||||||
The rivalry between Brighton & Hove Albion and Crystal Palace football clubs is often referred to asthe M23 Derby.[15][16]
The M23 is the only motorway in Sussex.
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