A23 road noise: how it affects nearby properties
The A23 is the principal London-to-Brighton route, running through south London and Surrey and on to the Sussex coast, with the M23 taking the fastest middle section. Dense housing lines its urban stretches through Croydon and Purley, while the Sussex sections towards Brighton pass through more open downland.
Traffic on the A23: what the 2025 DfT counts show
London's road to Brighton begins in Lambeth and stops at Old Steine, 51 to 53 miles depending on who is measuring, and its 99 DfT count points show modest flows with sharp exceptions. The median is 18,900 vehicles a day, 25 points are under ten thousand and a quarter are under 9,900. Only 17 pass fifty thousand and none passes a hundred thousand, though the highest count is 79,637 and the busiest tenth start at 65,100. The lowest is 1,160. Half the points fall between 9,900 and 30,600, on a span of just 75 km by the DfT's measure, so this is a road of ordinary A-road flows with a few strong exceptions.
Kennington Road, Brixton Hill and Streatham High Road give the A23 a south London start. Then the Purley Way bypass, opened in April 1925, takes it round Croydon, and Coulsdon's Farthing Way relief road, dated 2006 or 2007, took traffic out of that town centre. From Hooley to Pease Pottage the road is the M23, opened on 19 December 1974, so the A23 itself disappears. South of there it is dual carriageway round Gatwick and gained a third lane between Handcross and Warninglid in 2014. The southern third (45 points) has a median of 11,800 but a maximum of 79,637; the middle third, 20,200 and 71,380; the northern, 34 points, 20,600 and 34,524.
Lorries are scarce on the A23. The median share is 2.6 per cent, one point in ten has more than 4.6, and the highest in the data is 6.3, with 0.4 the lowest. A narrow band like that means the 2.6 per cent in the indicative table is a fair stand-in along the whole road, and differences between addresses come mainly from flow and distance.
| Quarter of points carry under | 9,900 vehicles/day |
|---|---|
| Median point | 18,900 vehicles/day |
| Three-quarters carry under | 30,600 vehicles/day |
| Busiest tenth carry over | 65,100 vehicles/day |
| Busiest single point | 79,637 vehicles/day |
The A23 on the ground
- Runs roughly 51 to 53 miles from Lambeth in London to Old Steine in Brighton; sources give slightly different figures. en.wikipedia.org
- Through south London it follows Kennington Road, Brixton Hill and Streatham High Road, then takes the Purley Way bypass, opened in April 1925, around Croydon. en.wikipedia.org
- The Hooley to Pease Pottage stretch is M23 motorway, opened 19 December 1974, so the A23 itself is replaced by motorway for that length. roads.org.uk
- The A23 becomes dual carriageway as it diverts around Gatwick Airport, and the Crawley bypass keeps it out of the town. en.wikipedia.org
- A third lane was added between Handcross and Warninglid, and the widened A23 opened to traffic on 7 October 2014. gov.uk
- Coulsdon's Farthing Way relief road, dated 2006 or 2007, was built to take traffic out of the town centre. en.wikipedia.org
How loud is the A23, and how fast does it fall away?
Taking the A23's open-ground rows in turn, a typical section at 18,900 vehicles a day gives 67 dB Lden at 20 m from the nearest carriageway, 64 dB at 50 m, 61 dB at 100 m and 58 dB at 200 m. A busy section at 65,100 a day gives 72, 68, 66 and 63 dB. All eight are above 55 dB, the Defra reporting figure, and above WHO's 53 dB guideline. They assume level, unscreened ground and 50 mph, which will not be right through Croydon or on the dual carriageway round Gatwick, and low-noise surfacing or barriers, such as those added at Handcross, are not included.
| Flow | 20 m | 50 m | 100 m | 200 m |
|---|---|---|---|---|
| Typical section (18,900 vehicles/day) | 67 | 64 | 61 | 58 |
| Busiest tenth of sections (65,100+ vehicles/day) | 72 | 68 | 66 | 63 |
Areas near the A23
Passing through: Greater London · Surrey · West Sussex · Brighton and Hove.
Residential Croydon, Purley and Coulsdon sit close to the busy northern sections, often with existing barriers, while the approach to Brighton crosses the South Downs. AcoustaPlot calculates a terrain-aware road level for your specific address along the A23, distinguishing the exposed roadside homes from those sheltered by cutting or distance.
Recent on the A23
When the A23 was widened to dual three lanes between Handcross and Warninglid in West Sussex (opened October 2014), National Highways installed low-noise road surfacing and purpose-built noise barriers — its own five-year follow-up evaluation confirmed noise levels stayed within predicted limits.
Source: https://nationalhighways.co.uk/media/a1whuxjd/a23-handcross-five-year-post-opening-evaluation.pdf
How AcoustaPLOT assesses A23 noise for your property
A road that shifts from London streets to motorway-replaced stretches to downland needs local data. AcoustaPLOT looks for one of the 99 DfT count points on the A23 itself within 8 km along it. Because the M23 replaces the A23 from Hooley to Pease Pottage, the count points on this page cover the other lengths only. It takes that point's flow and lorry share, then adds the real distance, terrain, ground, buildings or barriers, and any other roads or rail nearby. 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 A23 →
A23 noise: common questions
What happens to the A23 between Hooley and Pease Pottage?
That length is M23 motorway, opened on 19 December 1974, so the A23 itself is replaced by motorway there. The A23 counts described here, 99 points in all, are therefore for the other lengths. The A23 becomes dual carriageway as it diverts around Gatwick Airport, and the Crawley bypass keeps it out of the town.
Did the Handcross to Warninglid widening stay within its noise predictions?
National Highways' five-year follow-up evaluation confirmed noise levels stayed within predicted limits after the third lane was added, with low-noise road surfacing and purpose-built noise barriers installed. The widened road opened to traffic on 7 October 2014. Those are measures taken on the ground, and the open-ground table includes neither surfacing nor barriers. The wider A23 median is 18,900 vehicles a day.
How old is the Purley Way bypass around Croydon?
The Purley Way bypass opened in April 1925 and carries the A23 around Croydon, while through south London the route follows Kennington Road, Brixton Hill and Streatham High Road. At Coulsdon, the Farthing Way relief road, dated 2006 or 2007, was built to take traffic out of the town centre. In the counts, the northern third has 34 points, a median of 20,600 and a maximum of 34,524.
Which part of the A23 is busiest in the DfT counts?
The southern third, towards Brighton, has the highest single count at 79,637, yet its median is just 11,800 across 45 points. The middle third's median is 20,200 with a peak of 71,380. In all, 17 of the 99 points pass fifty thousand, so the peak readings are isolated rather than typical.