4 Conclusions and Further Work

4.1 CONCLUSIONS
The conclusions from this study are as follows:

1. 103 road links have been surveyed. On 23 of these, houses have been found less than 10m from the kerb. Over 1,300 houses were found in the field survey on these 23 road links.
   
   
2. Most of the road links surveyed were within the commercial districts of the cities, were dual-carriageways and were ring roads or major radial routes.
   
   
3. Where houses have been found, further analysis has been undertaken using postcode data. It has been estimated that the road links examined have a total of 2,600 residential delivery points on them.
   
   
4. A range of 1,300 to 2,600 households has therefore been estimated for those links surveyed. The average size of a UK household is 2.7 people, giving a total of about 3510 to 7020 people exposed along these road links. This does however represent an over estimate of the exposed population because they are not all within 10 m of the kerb. The postcode data does not provide this level of accuracy.
   
   
5. A comparison of local and national traffic flow data for Manchester, Salford and Birmingham has been undertaken. This has shown that the datasets of actual flow measurements in Manchester and Salford correspond reasonably well with the national data, whereas modelled traffic flows on road links in Birmingham show considerable differences from the national dataset.
   
   
6. A comparison has been made between predicted roadside NO₂ concentrations for 2005 using the local traffic flow data and that using the original national figures. 71% of the links analysed in this way have been estimated to have concentrations based on the local trafic flow data within a 10% range of the national modelled NO₂ concentration.
   

4.2 SUGGESTIONS FOR FURTHER WORK
Further work could be carried out to provide a more complete analysis of potential population exposure to roadside concentrations of NO₂ or other air pollutants. Additional detailed GIS data should be available from the Ordnance Survey on:

• postcode address points,
  
• road centre line locations and
  
• 'Landline' data showing locations of buildings.
  

The detailed ground truth survey data obtained during the current study could provide an excellent comparison with detailed GIS or aerial photography analysis.
It is recommended that additional work be carried out to compare these methods of analysis with the results of this study so that a robust and systematic technique can be developed for use on subsequent reviews of the NAQS.

References

DETR et al (1999) Review of the National Air Quality Strategy Department of the Environment, Transport and the Regions, The Scottish Office, The Welsh Office, Department of the Environment Northern Ireland. The Stationary Office, January 1999.

Hutchinson, D. and Clewley, L. (1996) West Midlands Atmospheric Emissions Inventory, London Research Centre.

Stedman JR, Bush T and King K (1998). An empirical model for estimating roadside nitrogen dioxide concentrations in the UK. AEA Technology Environment, National Environmental Technology Centre. Report AEAT-4291.

Results         Appendix 1

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Report and site prepared by the National Environmental Technology Centre, part of AEA Technology, on behalf of the UK Department of the Environment, Transport and the Regions