What Is Strategic Noise Mapping?

Strategic noise mapping is the government's five-yearly computer model of environmental noise across England. It estimates how much noise major roads, major railways and large urban areas produce — hour by hour, averaged over a year, on a 10-metre grid. The current version is Round 4, based on 2022 data. It exists because of a 2002 EU directive (the Environmental Noise Directive, kept in UK law after Brexit as the Environmental Noise (England) Regulations 2006), which requires governments to map noise exposure and draw up action plans.

If you've just searched a postcode on this site, the bands you saw come directly from that model. This guide explains how the model works, what the measures mean, and — just as important — what it deliberately leaves out.

Who makes it, and how?

The Department for Environment, Food & Rural Affairs (DEFRA) commissions the mapping. Nobody drives around England with microphones: the model combines traffic flow counts, vehicle speeds, road surfaces, railway timetables and rolling stock, terrain height, and building outlines. From those inputs, standard acoustic calculation methods (CNOSSOS-EU, since Round 4) compute how sound propagates outward from each road and railway — including how it reflects off and is screened by buildings.

The output is a grid of predicted noise levels at 4 metres above ground, every 10 metres, across the whole country. That height matters: 4 m is roughly first-floor window height, the standard for comparing exposure, so ground-floor levels behind a garden wall can be lower than the map suggests.

What do LAeq,16h and Lnight mean?

Two measures matter on this site:

• LAeq,16h— the equivalent continuous sound level across the 16-hour day, 07:00–23:00. Think of it as all the day's noise energy smoothed into one steady level.
• Lnight — the same idea for the 8-hour night, 23:00–07:00, averaged over a full year. This is the measure the World Health Organization uses for sleep-disturbance guidance.

Both are reported in bands — 55.0–59.9 dB, 60.0–64.9 dB, up to 75 dB and above for day, starting at 50 dB for night. An average hides variation: a 60 dB LAeq,16h road might be near-silent at 6am and much louder than 60 dB during the rush hour.

What counts as a "major" road or railway?

The regulations only require mapping of roads with more than about 3 million vehicle passages a year (roughly 8,200 a day — most A-roads and all motorways) and railways with more than 30,000 train passages a year, plus all noise sources inside large urban areas ("agglomerations"). That threshold explains the most common surprise on this site: a postcode on a busy-feeling B-road showing no mapped noise at all. Across our dataset of 1,492,853 England postcodes, only about 28% currently sit inside a mapped road-noise band — not because England is quiet, but because the mapping is selective by design.

What the model leaves out

• Local roads below the traffic threshold
• Neighbours, pubs, music venues and street noise
• Construction sites
• Aircraft (mapped separately per airport by the CAA and airport operators — not yet on this site)
• Industry outside large urban areas

You might think a blank result means a quiet spot — actually it only means no modelled major sourcereaches the reporting threshold there. We repeat this on every result page because it's the single most important caveat in the data.

How accurate is it?

For long-term averages near major sources, strategic mapping is considered reliable enough to drive national policy — it decides where noise barriers, quieter road surfaces and planning conditions get priority. At the scale of one address it is less precise. The model predicts at grid points, not at your window; screening from one building, an acoustic fence, or which side of the property your bedroom faces can shift real exposure by several dB. Treat a band as "what the official model expects for this location", not a certificate.

Round 4, 2022 — and what happens next

Rounds run every five years: Round 3 covered 2017, Round 4 covers 2022, and Round 5 is expected around 2027. Everything here states its vintage because a lot can change in five years — new link roads, rail electrification, developments. When Round 5 is published we'll refresh the whole dataset.

What you can do with it

• Check any England postcode for mapped road and rail noise, day and night.
• Compare areas before renting or buying — our buyer's guide shows how to combine the map with a viewing checklist.
• If you're already living with road noise, see your options — from glazing to reporting to your council.