Table 1

Land use regression model for NO₂ in TRAPCA 1999–2000, based on 35 sites, used in both TRAPCA 1999–2000 and TRACHEA 2007

Variable	Parameter estimate	SE	p Value	VIF
Intercept	13.16	1.74	<0.0001	–
Addresses in a 300 m buffer	0.004397	0.001734	0.0169	2.02
Addresses in a 300–5000 m buffer	0.00005757	0.00002160	0.0124	2.60
Roads of BASNET categories 1–3 in a 250 buffer	0.6730	0.1476	<0.0001	1.22
Region West^*	7.656	2.053	0.0008	2.07
Region Middle^*	8.218	2.015	0.0003	1.64

* Region North is the reference region.
VIF, Variance Inflation Factor; L1OCV R², the R²-value resulting from leave-one-out cross validation; TRACHEA, Traffic Related Air pollution and Children's respiratory HEalth and Allergies study; TRAPCA, Traffic Related Air Pollution and Children's Asthma study.