Kabul city (capital of Afghanistan) is one of the fastest growing cities in the world. This city is suffering from a highly congested traffic, caused by a dramatic increase of its population and a growing flow of economy during the last decade. This research is a very important and initial step towards transportation planning of Kabul city. In this research, the travel demand of Kabul city has been analyzed and forecasted for the current year of 2015 and mid-term future year of 2025. Traffic assignment analysis and a simulation were performed to comprehend the main causation of congestion. The results signify that the private transportation demand is less than the physical capacity of road network in Kabul city. Thus, in the short term there is no need to introduce any new link to the road network of Kabul city and the actual capacity of the road network should be raised to reach its physical capacity by developing the road infrastructure and improving the traffic management. On the other hand, the traffic assignment results pinpoint that the main factor in creating congestion in Kabul city is the large proportion of public transportation demand. Therefore, it is recommended that high capacity public transportation facilities should be introduced to the highly required links as shown in the study. The simulation results indicate that in the long-term the travel time will dramatically increase by the growth of population. Hence, in the mid-term future (2025) the capacity of highly congested links should be improved by introduction of new links. The data for analyzing transportation of Kabul city is not fully sufficient, yet this study can quantify the large scale transportation problems. At the end of the study, the required transportation data is quoted, which is to be gathered for more precise results.