As part of the expansion of Gatwick Airport which may increase passenger throughput by 20% by 2038, there are proposed change to the road network near to the airport. This is an early stage of consultation, so these plans are likely to change before permission is granted not before 2024.

M23 Spur

It is proposed that the M23 Spur will be widened to 3 lanes Eastbound for its entire length (800m). This will be carried out within the current highway boundary by removing the current hard shoulder, however may require some works to be carried out to the current embankments to facilitate this.

The M23 Spur was widened to 3 lanes Westbound in 2020 as part of the M23’s SMP, with the removal of the hard shoulder and a fixed limit of 50mph, no additional technology was added, or planned to be added to the spur due to its short length. These works will likely make the Eastbound carriageway mirror the Westbound with an introduction of a 50mph fixed limit.

Airport Way Roundabout East (Southern Terminal Roundabout)

Junction 9a of the M23, known as Airport Way Roundabout East, or in this consultation as the Southern Terminal Roundabout is located between the M23 spur and the A23 Spur (Airport Way). It is proposed that this roundabout is turned into a standard grade separated roundabout interchange, with the M23 spur gaining a flyover. To accommodate the slip roads, the bridge currently at Balcombe Road (B2036) will need to be modified, if not completely rebuilt. This bridge is currently two span in the event it was dualled, it will be interesting to see the new bridge(s) will be two span now too.

All slip roads, other than the diverge westbound will be of a single lane layout (although wide enough for 2 lanes for use during construction). The diverge westbound will be dual lanes with a tiger tail. The junction will operate as a lane drop as the M23 spur will be 3 lanes, with the A23 spur (Airport Way) is only two lanes.

The flyover will be built to standards that allows 50mph running, other options did include 40mph design speed, but 50mph was chosen instead.

The Airport ring road also appears to be widened to 3 lanes, although this may just be for illustration purposes, likewise the roundabout is three lanes, whilst it only needs to be two. Minor road changes within the airport sites have not been published as this scheme is for “Ground access” to the site only, and not about the site’s layout. Internal road layouts will likely be published in final stages of the application.

Its interesting to see that the junction is planned to be built as a roundabout interchange, while a trumpet junction would be better, especially as it could be a tight radius due to the low speed environment of airport ring road (30mph). However a roundabout does allow a northern arm to be built in a future date (an option was to build this arm as part of the scheme, but was not chosen.) A temporary northern arm may exist during construction to facilitate the construction compound.

The main issue with the current proposal is between the merge from A23 (London Road) onto Airport Way and the diverge Eastbound at J9a is less than 275m nose to nose. Leaving about 200m weaving room. The speed limit of Airport Way is proposed to be lowered to 40mph (currently 50mph), even at 40mph that only leaves about 11 seconds. In low traffic this is not an issue, but constrained by the railway bridge, it may be that Airport Way / London Road Merge would need to be traffic signal controlled (part time) to function safely.

Airport Way Roundabout West (Northern Terminal Roundabout)

Airport Way Roundabout West, or in this consultation as the Northern Terminal Roundabout is located on the Western end of the A23 Spur (Airport Way) and has limited access to the A23 (London Road), using Longbridge Roundabout to facilitate more movements.

It is proposed to remove the roundabout entirely and replace it with two traffic signal controlled junctions, a fly over and a few merges/diverges. It does look like a mess, but it is an overall improvement than its current layout. The new fly over will mean that A23 Spur (Airport Way) to A23 (north) will be entirely free flowing in both directions.

There are some issues that I do see with the current proposals:

  • A23 Spur (Airport Way) to A23 (London Road) North is a diverge, whilst it ends in a lane drop split into Perimeter Road North & North Terminal Approach getting 1 lane dedicated each. I think it would be better to be a lane drop onto the new fly over with 1 lane continuing to the next junction where an aux diverge lane could be provided.
  • A23 Spur (Airport Way) to A23 (London Road) South still has to u-turn at Longbridge roundabout, or use Perimeter Road North
  • No access to Northern terminal from A23 (London Road) Southbound from Horley. This could be provided at the new traffic signals on the A23 (London Road).
  • NMU provision has been omitted

Longbridge Roundabout

Some small changes are proposed at Longbridge Roundabout. These changes are mostly providing more lanes on the roundabout as well as additional signalisation and cycle/foot provision. The roundabout is still needed to be used to carry out u-turns when heading towards Crawley from M23 J9, although the airport perimeter road can be used but discouraged.

A23 London Road to Perimeter Road Link

No official name for this junction, but it is proposed to move the small link road between the A23 London Road & Perimeter Road about 100 meters South to use the roundabout by Queens gate, rather than a separate junction just to the north where it currently it. It is unclear why this change happening, although I suspect it is something to do with weaving lengths to the diverge further North.

This will impact of the current cycle track coming off the roundabout, and the plans do not show what will happened to the current dedicated cycle track (with moped access – the only one in Sussex)

NMU Changes

GAL has said they are committed to improve foot and cycle access around the airport and to provided additional cycle parking and shower & locker rooms. However little has been announced in terms of where these improvements will be. These routes will likely be announced in a later consultation and improve cycle access to and from Horley & Crawley.

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