Lets look at some roads in Cornwall the numbers are in AADF (Annual Average Daily Flow).
We have Treswithian junction on the A30. From 21,396 in 2000 total vehicle numbers rise to over 32,000 in 2009 and 2010. But then they fall back to just over 24,000 in 2015, a fall of a third. Odd.
On the A30 at Connor Downs numbers increase from 22,200 in 2000 to 26,300 in 2003, then fall back before rising above 26,000 from 2012 onwards.
The A30 at Marazanvose and St. Erth shows continuous increases from 2000 to 2015 – 17,600 to 21,300 and 16,300 to 21,200. Looks credible.
The A30 at Canonstown – 21,200 in 2000, goes up to 23,400 in 2004 and then falls back to 16,400 in 2010 before picking up again to stand at 19,500 in 2015.
Then we have the A39 to St. Austell from Truro. In 2001 it recorded 19,600, but then with some ups and downs has declined and in 2015 the figure was – 14,500. How odd?
On the road from Chiverton to Threemilestone, 19,000 in 2000 then 22,700 in 2009 stable but falling to 17,700 in 2015?
In the Camborne-Redruth area we have the B3303 to A3047 Tolvaddon Rd. This sees an increase from 19,200 in 2000 to 24,300 in 2006 and then the numbers fall back to 19,500 in 2009 and 2010, pick up slightly in the following two years before dropping to 16,000 in 2013 then a small increase to 16,600 in 2015.
Then at Treswithian junction we have 21,400 in 2000 32,600 in 2009 and then mysteriously falls back to 24,300 in 2013 before recovering slightly to 24,700 in 2015!
How do we explain these changes? A downturn in some areas in some years due to the recession – sounds plausible. But falls on other roads – in Camborne-Redruth the impact of the East West link road – perhaps on some roads.
But again the impression is that traffic figures do not accord with peoples everyday experiences.
For the original data: http://www.dft.gov.uk/traffic-counts/cp.php?la=Cornwall+excluding+Isles+of+Scilly