Geographical information systems aided traffic accident analysis system case study: city of Afyonkarahisar

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Abstract

Geographical Information System (GIS) technology has been a popular tool for visualization of accident data and analysis of hot spots in highways. Many traffic agencies have been using GIS for accident analysis. Accident analysis studies aim at the identification of high rate accident locations and safety deficient areas on the highways. So, traffic officials can implement precautionary measures and provisions for traffic safety. Since accident reports are prepared in textual format in Turkey, this situation makes it difficult to analyze accident results. In our study, we developed a system transforming these textual data to tabular form and then this tabular data were georeferenced onto the highways. Then, the hot spots in the highways in Afyonkarahisar administrative border were explored and determined with two different methods of Kernel Density analysis and repeatability analysis. Subsequently, accident conditions at these hot spots were examined. We realized that the hot spots determined with two methods reflect really problematic places such as cross roads, junction points etc. Many of previous studies introduced GIS only as a visualization tool for accident locations. The importance of this study was to use GIS as a management system for accident analysis and determination of hot spots in Turkey with statistical analysis methods.

Introduction

Today, the most negative results of developing modern transportation systems are road accidents with injuries and loss of lives. So, traffic safety is the most critical matter in agencies’ transportation strategy. The identification of safety deficient areas on the highway network is aimed at a comprehensive safety program by traffic officials. One of the most important problems that traffic officials face is where and how to implement precautionary measures and provisions so that they can have the most significant impact for traffic safety (Khan et al., 2006). GIS is a very important and comprehensive management tool for traffic safety. Since 1990's, GIS technologies have been used more frequently for such studies due to the availability of low cost GIS with user-friendly interfaces (Khan et al., 2006). GIS has the ability to hold a vast amount of data that can be easily stored, shared and managed. It provides a platform for data analysis and visualization to explore relationships between data, and it can easily provide graphical or non graphical outputs. Meanwhile with the rapid development and adoption of GIS technology as a tool to manage, explore, analyze and visualize spatial data, spatial data analysis methods that are included in GIS software's modules, received increasing attention (Booth, 2004). The importance of spatial analysis is the measurement of attributes and their relationships, taking into account the spatial location of the phenomenon under study (Camara et al., 2001). Spatial data and its analysis is one of the most important information for traffic accident analysis. GIS aided spatial data and spatial analysis provides a lot of information to analysts about hazardous locations, hot spots, warm spots etc. Using GIS, the analyst can merge accident and highway data, geocode the accident data and locations, calculate frequency and rate of accidents, select a variable for stratification to calculate mean and standard deviation of accident rates (Liang et al., 2005).

Identification of safety deficient locations with GIS aided spatial analysis will certainly help to decrease the traffic accidents. But the success of these analyses depends extensively upon accuracy, reliability and comprehensiveness of the traffic accident reports. So, the accuracy and comprehensiveness of traffic accident reports is very important for inputting data and spatial analysis for improving traffic safety analysis. Today there is no consensus among countries which necessary items should be included in traffic accidents reports (Demirel and Akgungor, 2002). Recently, Khan et al. (2004) examined the accident report forms used by the Police in various counties and they found that these report forms yield up to 99 different pieces of information related to accident environment (Loo, 2006). However, the accuracy and quality of these data are not good enough. Hence, one cannot determine to what degree this impacts the improvement of traffic studies.

Afyonkarahisar is a junction point connecting the developed big cities, industrialized centers and touristic areas in Turkey (Fig. 1). Especially in summer, vehicles traveling on the highways have been increasing dramatically compared to other seasons. Hence, traffic accidents have become more common. So, it is an urgent task to reduce these accidents by performing analysis and taking precautions. The aim of this study is to establish a GIS aided system to determine hot spots and factors contributing to accidents in these locations and to determine how, what, and where accident countermeasures can be implemented using a GIS.

Section snippets

Literature review

GIS-based accident information systems can identify relationships between spatial phenomena that are almost impossible to determine with a non-spatial database. Since 1990, there have been many studies about GIS technologies and its applications on traffic safety and accident analysis as a spatial pattern. Many agencies and researchers have reported the use of GIS analysis of accidents. The types of analyses, applicable for accident analysis, include intersection analysis, segment analysis,

Methodology

Afyonkarahisar is located in a junction point of industrial, tourism and agricultural areas in Turkey. Especially, in summer with expatriates coming from abroad, traffic density increases comparatively. Meanwhile, weather related crashes happen frequently because of continental climate in the region in winter (Fig. 2). The length of the highways is approximately 400 km in the district. 85% of these highways were two lanes until 2005. Average rate of deadly accidents in the province is about 2.5%

Conclusion and discussion

After determining the hot spots, we explored the accident conditions at these locations. As mentioned above, accident density increases in summer and winter time. Especially in the summer, based on increasing traffic density, fatal traffic accidents occur more frequently. Traffic accident densities are the most in summer in August, and in winter in December. When we examined the traffic accident frequencies on daily base, Friday, Saturday and Sunday, were higher frequencies than other days (

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