The Netherlands has been given a warning by Brussels because the air quality is substandard. KEMA has developed a model that can perform a detailed calculation of the local effects of traffic and environmental zoning plans on the concentration of fine particles and oxides of nitrogen. On the basis of projects that have been carried out with this STACKS model, the local pollution appears to be many times better than previously believed. This offers perspective for expansion plans. 

The European Commission has established limits for the allowable concentrations of fine particles and oxides of nitrogen in the member states. The guideline for fine particles became effective this year; the guideline for nitrogen dioxide becomes effective in 2010. At this moment, the Netherlands already exceeds the norms. For this reason, innumerable plans for new industrial areas and traffic routes have been frozen by the courts. The problem is so serious that a National Debate has been organized for 26 September, followed by a technical Background day on 13 October.

Realistic model
In a number of cases, the problems have been caused by the use of the screening model that is often used. This model, once developed primarily to prevent polluting "hot spots" from being missed, is actually a quick-scan model. It provides a conservative, and therefore often overly pessimistic, picture of the situation.

KEMA has developed a numerical model that generates a more realistic and more detailed image of the actual contamination. This model, based in part on data from the national measurement network of the RIVM, includes the newest insights into air quality. The so-called STACKS model can calculate the effects of plans such as new industrial areas or traffic routes on the emission of fine particles and oxides of nitrogen. Last year, KEMA used this method to calculate the effect of reduced highway speeds on air quality.

In cooperation with engineering bureau Tauw and traffic-research agency Goudappel Coffeng, KEMA has carried out countless numbers of calculations for municipalities, provinces and the Dutch Directorate for Public Works and Water Management. The results have shown that the local contribution to air pollution is sometimes better than expected, although not always. Through the use of this model, it would not be necessary to freeze so many of the new environmental zoning projects. During the Background day, a KEMA expert will provide additional information on this topic.