Distribution of trip length for shopping purposes. The graph shows population counts by trip length (1 km intervals) for observed travels to hyper/supermarkets (green), grocery stores (orange) and bakeries (blue). Trip lengths are Euclidean distances between administrative centres of municipalities. Dots represent observed values; lines are Gaussian probability density functions. Trip lengths distribution shows a bell-shaped pattern with an under-representation of population counts for short distances. This can be due to the absence of data for intra-urban travels and a possible spatial structure effect (i.e. relatively few centres of municipalities situated less than 2 km away one from the other).