The Select Committee were right to call on the Department for Transport to come up new estimates of how many people would be impacted by a third runway using the most up-to-date contours. At present, as I indicate below, it is very messy.
Contours are created by averaging the noise out over a 16 hour day. Until very recently, the Government argued that the 57 decibel contour marked ‘the onset of community annoyance’. Following the SONA report it commissioned from the CAA, this has been revised down to a 54 and 51 contour. The Guardian report was based on the numbers in a 45 contour (which has not been used before and is lower than the WHO currently regards as problematic).
Percentage of population severely annoyed by aircraft noise
57 contour (approx 9 miles from Heathrow) 13%
54 contour (approx 13 miles) 9%
51 contour (approx 17 miles) 7%
45 contour (unknown, but probably over 25 miles) 2.5%
National Policy Statement 2017
(using the 54 decibel contour)
Without 3rd runway With 3rd runway Difference
2030 560,000 650,000 + 92,700
2040 475,000 515,000 + 45,000
2050 430,000 475,000 + 45,000
The Transport Select Committee Report 2018 found thatif the 51 decibel contour was used the total number of people in the noise annoyance footprint in 2030 with a third runway in place would be 1.15 million.
The Guardian article reflects the number of people who would be impacted with a 3rd runway in place using a 45 decibel contour. The number would be 2.2 million in 2050.
The Department for Transport put out this statement yesterday to confirm it: The figures referenced include everyone that will experience any change in noise level, including those below the Lowest Observed Adverse Effects Level of 51dB LAeq and even those below 45dB LAeq.
What we lack are figures about how many people currently live within the 45 or 51 decibel contours or how many would in 2030 and 2050 if a 3rd runway is not built. This means no comparisons can be made. Almost certainly, though, the numbers currently within a 45 decibel contour will be over 1.5 million.
by John Stewart