Background to air quality in South Northamptonshire
Air quality throughout the district is generally good although there are areas where nitrogen dioxide levels are close to, or exceed the national air quality objective. This poor air quality is largely related to vehicles on and around busy roads.
In September 2005 an Air Quality Management Area (AQMA) was declared in Towcester centre as a result of the annual mean air quality objective for nitrogen dioxide being exceeded. The air quality action plan for Towcester town centre was finalised in October 2008 and is currently being updated.
Whilst the A5 through Towcester carries relatively few vehicles, compared with the M1 or A43; the cause of the air quality exceedance is attributed to the slow moving through traffic on the A5, along with poor dispersion of pollutants due to the narrow road and high buildings. There is a local significant contributory factor of roadside and Market Square parking interrupting the smooth flow of traffic.
Road traffic statistics have shown an increase in the percentage of heavy goods vehicles on the trunk roads besides an increase in traffic generally. In addition, diesel vehicles are emitting a higher fraction of primary nitrogen dioxide nationally, especially where particulate traps are fitted.