Analyzing the Presence of Risk Factors in Vulnerable Areas

Because of present conflict patterns and changes in the type and form of military threats, civilian and military threats of Iran are impressive. Accordingly, defensive considerations of cities as the centers of national or regional impact are essential. These parameters can be used in different areas of the city in order to maintain the structural and physical infrastructures and the vital arteries of the city. The public transport network is one of the vital arteries and the determining factor of the city, which is necessary to continue to maintain the city. Among the various types of urban transport, terrestrial communications network and related infrastructure (urban road network), as the broadest, most general and most accessible form of transport, has particular importance and decisive. Because of the importance of this issue, in the periods of urban attacks and after that, the roads are very vulnerable and their performance can be impaired or interrupted. Transportation system has many interconnected components such as bridges, tunnels and passageways, which their damages can reduce total system performance and cause various problems and issues. Improvement of the vulnerability of transport systems requires the use of special solutions. In order to reduce vulnerabilities and facilitate the management of crisis, it is necessary to identify the vulnerabilities of each urban element, so through the strengthen of these areas, we can reduced vulnerability. There are different ways to identify vulnerabilities, however, in this study, a model is presented to identify vulnerable areas of urban roads. As a sample case it has detected vulnerable parts of Sadr Elevated Expressway in Tehran. Sadr Elevated Expressway with a length of approximately 5 km located in northern Tehran. It is part of the border of 1 and 3 area of Tehran. The study area is located in the highlands of Tehran; the slope of the region is about 10%. For the expansion program of Tehran, the highway was built after the Islamic Revolution and then it was developed. With regard to the development of this highway and elevated expressway construction, risk in this area is increased. To increase traffic volume on the highway, bridge was designed on the 5th kilometer. Although, this work would increase traffic volume it has increased the vulnerability. There is a long bridge along the highway which is the main reason of risk. Since the bridges are very vulnerable, the massive structures must be protected against threats. Hazards generally can be divided into two categories: natural and man-made and in the beginning, these threats should be classified in the best way. Initially to identify vulnerabilities in Sadr expressway, impact indicators were found. Vulnerability parameters of the pathway have to be identified and weighted. The general index of the vulnerability indices of the highway will be divided into the three main categories. Defense indices, urban indices and natural indices and each of the indices and sub-indices will be rated using AHP and TOPSIS methods. The main method used in this research was the hierarchy process, but to test the results of this method, the TOPSIS process was also applied. After that, for both methods questionnaire was prepared to find out the expert's opinions. In order to locating weak spot, first, some parameters will be declared and layered data and maps will be produced in ESRI-ArcGIS desktop package, after that weighted maps will combined together and vulnerability maps of the expressway will be created. The map showed hazard zones along the highway to find out the most vulnerable point. The study area is characterized the presence of risk factors in vulnerable areas is very impressive. Most of these factors increases the damage and also in the most vulnerable point of the study area various risk factors have come together, contains: gas pipeline, metro, canal and bridges. Therefore, to reduce the vulnerability these factors must be eliminated. As a result of this study, to reduce vulnerability in the study area is necessary to consider the following: • Move or Secure Facility near Highway; • Retrofitting Bridges in Areas with Greater Vulnerability; • Prevent the Construction of High-Rise Buildings along the Highway and Retrofitting Existing Buildings around the Study Area; • Immunization Risks around the Highway; • Design Alternatives for the Urban Streets, to be Continued Traffic of Highway in the Event of Failure; • Create Evacuation Routes in Case of Destruction Crossing the Highway, Like: U-turn on the Highway, Mobile Emergency Highway Exit etc.