Spatio-Temporal Analysis on Urban Traffic Accidents: A Case Study of Tehran City, Iran

Abstract

Urban Traffic Accidents (UTAs) may be seen as discrete events, localized in space and time. UTAs rates all over the world show great disparity, especially between developed and developing countries. Today, the most negative results of urban transportation are UTAs with many side effects such as injuries and loss of lives. UTAs lead to injury, death, disability and pain, loss of productivity, grief, social and mental problems. Proper and deep study and planning can enhance transport and driving safety and reduce number and severity of accidents. Traffic safety crises, death, damage and costs resulting from road UTAs are some of the most important public health and police organization challenges. In particular, UTA’s victims are often people who are aged 15 - 44 years old in Iran, and UTAs are the second cause of death after heart disease in Tehran. UTAs’ statistics in Tehran reveal a serious problem with significant fatality and injury rate. This study aims to identify the spatial pattern of UTAs in the city of Tehran in order to find the causes and consequences as well as the temporal and spatial or spatio-temporal variation of accidents. The relationship between the space and time of daily activities that generate urban daily trips and UTA, is examined in Tehran city for 2010 to 2011. The analysis is based on different primary and secondary data sources, which include locations of accidents and different attributes such as date, reason, kind, etc. Based on the data analysis, the study also attempted to show some light on the major causes, factors and types of accidents in order to identify the problem and suggest appropriate suggestions which reduce UTAs. As this study considered different factors of UTA, urban environment, land use, population, human activities and culture point considered as the most important pillars of this study. In order to understand knowledge, culture and attitudes of drivers towards traffic regulations, questionnaires were distributed to 1500 drivers in the study area to gather data about the drivers’ knowledge, beliefs, attitudes, and behaviors and 1177 of them returned. The results express that culture and knowledge of drivers have direct effects on localizing accidents. Furthermore, the concentration of educational, commercial and cultural activities that make up a large number of urban trips and urban dynamics, road usage, and time are among the main considerations of this study. The relationships between population, land use and dynamic patterns of city which constitute the urban structure, are used to establish a link between UTA and the urban structure of Tehran city. Time is considered as a crucial variable in this study that leads people to different kinds of locations and risk. Land use data and population data are combined with the accidents data using GIS techniques to generate relevant inputs for analysis. Concerning the methodology, cluster analysis techniques are developed to analyze the association between UTA numbers and land use categories and per 1000 residents of Tehran city. The techniques are developed to investigate the temporal variation of UTA over the time periods segmented into different zones. The results show that the suburban zone with industrial land use types and more highways are associated with more fatal and injured accidents. In comparison, the CBD zone is the safest not only in regarding the number of accidents but also in severity of accidents. Traffic limitation boundaries, wide pedestrians walking area and increased police checks, make this area safer despite the higher population density and daily activities. It was observed that the UTA spatial pattern changes dramatically in different zones and hours, especially during RH. Increased accidents but of lower severity happen in Tehran during the RH day when there is traffic congestion on transportation networks or roads and crowding on public transport is at its highest. Normally, this happens twice in a day, first in the morning and second in the afternoon-evening, the times during which the most people commute. It was observed that land use category, urban structure and population density make different rush hours in the city, therefore, different zones have different RHs. Referring to population movement or urban dynamic and urban structure, main roads types in urban and suburban zones become congested in different hours due to a large number of people activities. Thus, these different RHs in different zones result in different spatial patterns of accidents within the city. During Thursdays, the schools and administrative offices follow a half-day schedule and many people engage in recreation such as shopping and other extra activities. This causes a different type’s RHs in Thursdays as it takes some load from the evening RH, and thus makes the morning RH the most intense time of the day. In addition, this study provided an explanation on the relationship between urban structures, creating UTA in Tehran. It was discovered that the locational pattern of the various land uses in the urban area is a reflection of socio-economic and ecological factors. Furthermore, the spatial analysis and temporal analysis of relative accidents risks point out the risky segments for different zones of the city and different land uses depending on the season, month, day and time.