This paper attempts to explain the spatial variation of the use of a bicycle for commuting to work at the level of the 589 municipalities in Belgium. Regression techniques were used and special attention was paid to autocorrelation, heterogeneity and multicollinearity. Spatial lag models were used to correct for the presence of spatial dependence and a disaggregated modelling strategy was adopted for the northern and southern parts of the country. The results show that much of the inter-municipality variation in bicycle use is related to environmental aspects such as the relief, traffic volumes and cycling accidents. Town size, distance travelled and demographic aspects also have some effect. In addition, there are regional differences in the effects of the structural covariates on bicycle use: the impact of variables such as traffic volume and cycling accidents differs substantially between the north and the south of the country. This paper also suggests that high rates of bicycle use in one municipality stimulate cycling in neighbouring municipalities, and hence that a mass effect can be initiated, i.e. more cycle commuting encourages even more commuters in the area to cycle. These findings provide some recommendations for decision-makers wishing to promote a shift from car to bicycle use.

disparities opposing city centres and peripheries. In the US for instance, inner cities are usually poor and the catalyst of many social problems, whereas suburbs are more well-off. Brussels exhibits a similar spatial structure since its inner city concentrates unemployed workers and disadvantaged communities, including many unskilled workers and ethnic minorities (see for example, Vandermotten et al., 1999;Thomas and Zenou, 1999; GoffetteNagot et al., 2000;Kesteloot et al., 2001). Residential Segregation and Unemployment: The Case of BrusselsClaire Dujardin, Harris Selod and Isabelle Thomas [Paper first received, February 2003; in final form, March 2007] AbstractThis paper investigates the causal effects of the spatial organisation of Brussels on unemployment propensities. Using census data at the individual level, the unemployment probability of young adults is estimated while taking into account personal, household and neighbourhood characteristics. The endogeneity of residential locations is solved by restricting the sample to young adults residing with their parents; the potential remaining bias is evaluated by conducting a sensitivity analysis. The results suggest that the neighbourhood of residence signifi cantly increases a youngster's probability of being unemployed, a result which is quite robust to the presence of both observed and unobserved parental covariates.

Résumé L’objet de cette étude est de proposer une méthode de détermination des limites de l’agglomération bruxelloise inspirée par une revue des critères utilisés par les instituts statistiques nationaux de différents pays. Elle est basée sur un nombre limité d’indicateurs statistiques simples et faciles d’accès. Nous définissons ainsi l’agglomération bruxelloise comme un ensemble de communes densément peuplées ou qui possèdent une forte concentration d’emplois tout en présentant une dépendance fonctionnelle étroite avec la région de Bruxelles-Capitale, dépendance matérialisée par des déplacements domicile-travail importants. L’agglomération ainsi définie sur la base des recensements comporte un noyau de 31 communes, stable de 1991 à 2001. Une commune qui faisait partie de l’agglomération en 1991 en est sortie en 2001, traduisant une légère contraction de l’agglomération.

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