But the figures for overall decline mask a more complex localised picture with sharp falls in central areas and traffic increasing in the some outer eastern boroughs.
Traffic volume is measured through traffic flow, a calculation of the total number of kilometres covered by all vehicles. The calculations are done by the Department of Transport using data from the National Road Traffic Survey.
The significant decline in traffic flow is unique to London as only 3 other regions have seen modest falls and most have seen a growth.
The reduction is due to a 9% fall in car traffic while flows of other vehicles have increased by 2%. This reduced reliance on cars is in line with the falling ownership figures, particularly in central areas, as reported by Urbs.
The reduction in traffic flows is a long-term trend that has been steady since 1999 and does not appear to have been affected by the introduction of the congestion charge.
But last year saw a slight reversal with all vehicle flows up by 2%. Growing car traffic in East London played a part in this with increases of 10% in Waltham Forest and 6% in Redbridge.
Looking at the figures over 10 years, Redbridge along with Barking and Dagenham have seen the biggest increase in traffic flow, but the numbers are up across a swathe on North East London.
Elsewhere the numbers are falling with big declines in central areas led by 22% in Camden, but significant falls in outer areas such as 12% in Sutton and 11% in Croydon.