In order to minimize environmental impacts and to achieve sustainable development in route construction projects, environmental parameters must be considered. To achieve this goal, use of geographic information system for route selection was proposed. This research was undertaken for Rasht–Anzali railway in north of Iran as a case study. At first, environmental parameters that affect railway route selection were identified. These parameters include slope, geology, soil, land cover, rivers, roads and cultural heritage. Data related to these parameters were gathered or in some cases produced. Slope, rivers and road map produced from digital topographical map, at the scale of 1:25000. Landover map was produced from landsat7 ETM+ data dated on May 2000. Rectification of satellite data was implemented using ground control points method. To achieve a better resolution the multispectral bands were fused with ETM-Pan. Image classification was performed using a new approach (digital and visual). Maps such as geology, soil and cultural heritage were digitized. In order to determine the relative importance of these parameters in route selection, environmental and civil experts’ views collected from a questionnaire that has been designed for this aim. These views were used in pair wise comparison method to determine weight of map layers that related to these parameters. These weighted layers overlaid and a friction map was produced and automatically 4 routs resulted in GIS. Analytical Hierarchy Process was used to determine optimum routes in comparison with that produced in traditional method. Results indicate that the routes, which were designed using GIS method, are more environmentally sound than traditional one and represent a significant benefit for the decision maker. According to results of this investigation, applying GIS technology and inclusion of environmental experts views are recommended to minimize environmental liabilities.