- 1 - Paper presented at the 45 th Congress of the European Regional Science Association "Land Use and Water Management in a Sustainable Network Society" Vrije Universiteit Amsterdam 23-27 August 2005 Influences of the shape of a territory on the optimal locations of human activities? A numerical geography approach. PEETERS Dominique 1,3 THOMAS Isabelle 1, 2, 3 ( 1 ) Department of Geography, Université catholique de Louvain, Louvain-la-Neuve, Belgium. ( 2 ) National Fund for Scientific research, Brussels, Belgium. ( 3 ) C.O.R.E., Université catholique de Louvain, Louvain-la-Neuve, Belgium. Corresponding address: Isabelle THOMAS Department of Geography, Place Louis Pasteur 3 B-1348-Louvain-la-Neuve (Belgium) tel.: +32-10-47 21 36 Email: isabelle@geog.ucl.ac.be Abstract.- This paper aims at showing how far the shape of a studied area influences the results of optimal location-allocation models. Simulations are performed on rectangular toy- networks with an equal number of vertices but with different length/width ratios. The case of merging two such networks into a common market is also considered. We limit our experience to the Simple Plant Location Problem (SPLP) which captures the fundamental trade-off of economic geography between accessibility and economies-of-scales. Results are analysed in terms of locations, allocations and costs. On the average, we confirm that regions that are elongated require a greater number of facilities that those with a compact shape; this effect however depends upon the way a region is merged into a common market (type of border; relative position). The results help at understanding how far an area (country/region) has larger development problems than others just because of its shape and/or of the way this area is linked within a common market (elongation of the country and length of the common border). Key words: Location-allocation models; S.P.L.P.; regional development; shape; region.