Optimization of Urban Transportation and Study on Causes of Accidents, Yazd City, Iran

Introduction
Transportation as a prerequisite and basics of sustainable development has a key role in efficiency of facilities and human life. It has also played a significant role as an effective index in growth and development. The number of accidents in Iran is increasing and this carries with them a lot of financial, psychological, and social losses. Hence, it seems to be necessary to put into effect a series of executive solutions to prevent such catastrophes. Urbanization is being as one of the dominant contemporary processes as a growing portion of the global population lives in cities. Considering this trend, urban transportation issues are of foremost importance to support the passengers and freight mobility requirements of large urban agglomerations. Transportation in urban areas is highly complicated because of the modes involved, the multitude of origins and destinations, and the amount and variety of traffic. Cities are locations with a high level of accumulation and concentration of economic activities.They are complex spatial structures that are supported by transportation systems. The larger the cities, the greater are their complexity and potential for disruptions, particularly when this complexity is not effectively managed. The most important transport problems are often related to urban areas and take place when transport systems, for a variety of reasons, cannot satisfy the numerous requirements of urban mobility. Urban productivity is highly dependent upon the efficiency of its transport system to move labor, consumers, and products between multiple origins and destinations. Many different terms are commonly used to describe vehicle collisions. The World Health Organization (WHO) use the term road traffic injury, while the U.S. Census Bureau uses the term motor vehicle accidents (MVA), and Transport Canada uses the term "motor vehicle traffic collision" (MVTC ). Some organizations have begun to avoid the term "accident". Although auto collisions are rare in terms of the number of vehicles on the road and the distance they travel, addressing the contributing factors can reduce their likelihood. For example, proper signage can decrease driver error and thereby reduce crash frequency by a third or more. The aim of this research is to optimize the internal transportation of Yazd city with the use of multi-measurement decisive models.
 
Methodology
The method of this research is descriptive-analytical as a basical and developmental study. Multi-Criteria Decision Models are used for the expression of factors involved in the accidents. According to the documents, data and accident statistics have been collected for the study area. Techniques for measuring and analyzing the past few years can be give information about the root and contributing causes of the accident. Statistical techniques and multi-criteria decision making (Maximin, HurwiTZ) has been used in this resaerch. The case study of this research is Yazd City, as the capital of Yazd Province, Iran. At the 2006 census, the population of the city was 423,006 people, in 114,716 families. Because of of the need for adaptations to its desert surroundings, Yazd is an architecturally unique city.
 
Results and discussion
Growth of traffic in urban areas is linked with a growing number of accidents and fatalities, especially in developing countries. Accidents account for a significant share of recurring delays. As traffic increases, people feel less safe to use the streets.
The findings of this research show that 11000 accidents occur annually in different places of the city and 5% of them are with peddlers. The statistical analyses shows that in every kilometer of current roads of first and second degree as well as streets up to 60, 40, and 5 accidents occure annually. It is to be mentioned that the proportion of accidents per 10000 cars occur in the distance approximately about 400 kilometers. A study of network roads of Yazd shows that although the roads of these networks are suitable enough for different vehicles, some centeral streets such as Imam Khomeini (between Imam Sadegh and Abozar square) are resolved and considered as the critical exes. Yazd City has 22 crosses of 2, 3, and 4 times. The average time of green distance in all phases is 26 seconds. The overall average time of one cycle of road light for 2, 3, and 4 times is 55, 77, and 135 seconds, respectively. At present, there are 200 active buses in 48 bus lines and 140 taxies in 6 taxi lines. Out of these taxies, 15 are for railway station, 10 for airport, 30 for external roads, 20 for university, and 10 for bus station. A survey shows that in 2007 relative to 2006, the number of damaging accidents has been increased 5.69%, injuring accidents 7.5%, and deadly accidents 6.67%. The total accidents had been increased by 6.19%.
 
Conclusion
Nearly 3400 people are dying on the world's roads each day. Tens of millions of people are injured or disabled every year. Children, pedestrians, cyclists and older people are among the most vulnerable of road users.The most effective reasons for these accidents have been observance of predecence and paying no attention to the front. In all the accidents occured, personal cars and motor vehicles have been guilty of 12%. The highest number of accidents occured between10-12 O clock. The roads in which the accidents have occured are enumerated in order as following: Ayatollah Kashani, Jommhori Islami, Bulvard, Shahid Dashti Bulvard, Imam Khomeini Street, Shahid Motahari Street, Shahid Paknejad Street, Daneshju Bulvard, Shahid Sadoughi Bulvard, Azad Shahr Bulvard, Inghelab Street, and in the squares: Shahid Bahona, Imam Hossein, Shohadi Mehrab, Abozar, Abolfazal, Homafar,and Atlasi. Therefore, there must be a unit of safety management that can organizie the information and statistics to reduce accidents and promote common information in obtimizing safety. Obtimization of network roads, using better transportation means, supplying up to date transportion technology for supervising the drivers' faults, enhancement of signs, tables, and safety instruments of roads, optimization of the rules and regulations, promotion of public transportation system, and improved organization of the roads for vehicles are the only ways to get rid of such accidents.