M23 road noise: how it affects nearby properties
The M23 is the main route to Gatwick Airport, and its traffic pattern is shaped by airport access — with strong flows through the day and notable early-morning and late-evening activity. For homes near the M23, the combination of road noise and proximity to Gatwick flight paths can mean more than one noise source is worth checking.
Traffic on the M23: what the 2025 DfT counts show
Nine count points is a small sample, so every one matters. On the M23 all but one exceed fifty thousand vehicles a day, 8 in total, and 3 exceed one hundred thousand. None falls below ten thousand, and the lowest, 33,107, is already substantial. The median is 90,500 a day, the lower quartile 57,100, the upper quartile 114,500 and the top tenth begins at 118,600, with the busiest at 119,367. These are two way, year average figures, so airport peaks are smoothed into them. Eight of nine points in the busy bracket suggests a road that is consistently used rather than occasionally.
The M23 simply stops at Hooley, Surrey, where it merges into the A23 towards London; it was planned north to Mitcham but never built beyond. From there it runs about 16 or 17 miles to Pease Pottage in West Sussex, meeting the M25 at one of Britain's few four-level motorway interchanges, with the Gatwick Spur built alongside the southern section. Read from south to north, the first 3 points come in around 79,300, the middle 4 are the busiest at about 108,200, and the last 2 sit at about 73,800 though one reaches 114,480.
Lorries are a light presence here: the median is 4.9 per cent, the busiest tenth of points reaches 5.4, the highest is 6.1 and the lowest 2.2. The M23's identity as the Gatwick route means cars and airport traffic dominate, and the narrow band of lorry shares gives the calculation little variation to work with along the road.
| Quarter of points carry under | 57,100 vehicles/day |
|---|---|
| Median point | 90,500 vehicles/day |
| Three-quarters carry under | 114,500 vehicles/day |
| Busiest tenth carry over | 118,600 vehicles/day |
| Busiest single point | 119,367 vehicles/day |
The M23 on the ground
- The M23 runs from Hooley, Surrey, to Pease Pottage, West Sussex (roughly 16-17 miles), opening in 1974 and completed in 1975. en.wikipedia.org
- The M23 was planned north to Mitcham but never built beyond Hooley, where it merges into the A23 towards London. ukmotorwayarchive.ciht.org.uk
- The M23 meets the M25 at one of Britain's few four-level motorway-to-motorway interchanges, and the Gatwick Spur was built alongside the southern section. ukmotorwayarchive.ciht.org.uk
- J8 (Merstham) to J10 (Copthorne) is an 11-mile all-lane-running smart motorway with 12 emergency areas, a reinforced central barrier and noise barriers in built-up areas. nationalhighways.co.uk
- The scheme included a permanent 50 mph limit and all-lane running on the westbound Gatwick Spur between J9 and J9a, plus variable limits on J8-10. nationalhighways.citizenspace.com
How loud is the M23, and how fast does it fall away?
On open, flat ground with no screening, a home 20 m from the nearest M23 carriageway has an indicative Lden of 80 dB at the median flow of 90,500 vehicles a day. Moving out, the numbers are 77 dB at 50 m, 74 dB at 100 m and 72 dB at 200 m. At the busier flow of 118,600 they become 81, 78, 75 and 73. The inputs are 70 mph and 4.9 per cent lorries. Defra's reporting threshold of 55 dB Lden is well below all of these. The noise barriers built in built-up areas along the upgraded section are not in the table.
| Flow | 20 m | 50 m | 100 m | 200 m |
|---|---|---|---|---|
| Typical section (90,500 vehicles/day) | 80 | 77 | 74 | 72 |
| Busiest tenth of sections (118,600+ vehicles/day) | 81 | 78 | 75 | 73 |
Areas near the M23
Passing through: Surrey · West Sussex.
Residential areas in Crawley, Horley and Redhill sit close to the route, and some properties fall within range of both the motorway and airport-related noise. AcoustaPlot flags aircraft-noise proximity separately from road noise, so M23-area buyers get a clearer picture of which source — or combination — is likely to affect a specific address.
Recent on the M23
Between junctions 8 and 10, near Gatwick in Surrey, the M23 is a “controlled motorway” with variable mandatory speed limits introduced in 2020 — a step short of full “all lane running”, which applies only to the separate Gatwick Spur, not the main carriageway.
Source: https://www.legislation.gov.uk/uksi/2020/79/made/data.html
How AcoustaPLOT assesses M23 noise for your property
The M23 is short enough that a count point is rarely far away. Of its 9, AcoustaPlot picks one lying no more than 8 km along the motorway from the address and uses the flow and lorry proportion recorded. Distance to the nearest carriageway, terrain, ground, buildings and barriers, and other roads and rail are added. Aircraft noise near Gatwick is flagged separately from road noise, so a home between road and runway can see both. It reports the day-evening-night (Lden) and night-time (Lnight) levels at your facade, and reads Defra's mapped value for any railway noise where available.
Check my property near the M23 →
M23 noise: common questions
How does the Gatwick Spur affect homes near the M23?
The Gatwick Spur was built alongside the southern section of the motorway, and the westbound spur between J9 and J9a has a permanent 50 mph limit and all lane running. The spur is a separate carriageway, so the nearest carriageway to an address may be the spur rather than the main M23, which the calculation takes into account.
Does the J8 to J10 smart motorway include noise barriers?
Yes. The 11-mile all lane running scheme between Merstham and Copthorne has 12 emergency areas, a reinforced central barrier and noise barriers in built-up areas. The flat ground figures here do not allow for those barriers, so a home behind one could differ from the table in a way only an address level check can show.
Why does the M23 only reach as far as Hooley?
It was planned north to Mitcham but never built beyond Hooley, where it merges into the A23 towards London. Measured counts on this page cover only the motorway itself, about 21 km in all, so the northern end of the data stops where the A23 begins. Nothing here describes the A23 beyond that merge.
Which part of the M23 is busiest?
The middle section, with 4 count points centred on about 108,200 vehicles a day, is the busiest, and it holds the top reading of 119,367. The southern 3 points sit at about 79,300 and the two at the northern end at about 73,800, though one of those reaches 114,480, so even the lighter ends can be busy.