This manuscript presents an on-going research project, where the aim is to develop a Geographic Information System (GIS) based decision making method for supporting the sustainable transportation policies of Istanbul Electricity, Tramway and Tunnel General Management (IETT). The main approach is to design a spatiotemporal model for detecting the interaction between accessibility and land use before implementing a transport infrastructure investment and after its completion. In order to test the designed GIS-based model, a study area composed of eleven districts with high traffic density is selected at the European side of Istanbul. The designed system supports the integrated accessibility, connectivity and land use policies and aids to quantitatively measure the performance of investments that are among the priorities for transport decision makers.