جغرافیا و پایداری محیط (Feb 2021)
Evaluating Land use Mixed-ness on Street Level through Spatial Analyses and Gini Method
Abstract
The increasing use of motor vehicles is one of the consequences of urbanization, which in addition to problems such as traffic and air pollution, will reduce the physical activity of residents and affect the general health of society. As a result, one of the most effective ways to tackle this problem in recent decades has been to increase people's accessibility to a variety of land uses by reducing travel distance or properly mixing land uses. Therefore, this challenge has led various researchers around the world to seek new ways of urban management to solve this problem. One of the most significant approaches to increase accessibility is proper mixed land use in urban areas. This study aims to calculate equality in the distribution of urban uses along the street network of Valiasr neighborhood, located in District 6 of Tehran Municipality by using GIS as a spatial analyst tool and Gini index as an indicator for the level of justice in distribution. Based on the number of land uses among longitudinal deciles of each street, this analysis has determined the level of equality in the distribution of land uses by the Gini index, for each passage and the whole neighborhood. The findings show that the Valiasr neighborhood with a Gini index of 0.3 owns a relatively good equality in the distribution of land uses. In addition, a comparison of the results with the findings of other studies reveals that the Gini index of each neighborhood can be a good indicator to measure the landaus mixed-ness, walkability, and accessibility to urban and transportation infrastructure in a region. Besides, it can be used along with other factors in regional or urban planning due to the justice-oriented essence of Gini index. Extended Abstract 1-Introduction The growth of urbanization has caused insufficient attention to how different land uses are arranged and mixed, while the way different land uses are arranged determines the distance people should travel to meet their needs. Moreover, it will reduce traffic and related problems such as air pollution besides increasing the physical activity of residents and ultimately their health. The model presented in this research is able to examine the degree of mixing of different land uses, so the Gini index has been employed to examine the extent of distribution of land uses in each travel and to quantify this distribution. Compared to previous studies, the distinguishing feature of this study is considering the distance of land uses in calculating the amount of dispersion, which will lead to a proper evaluation of the results obtained. 2-Materials and Methods The present study intends to provide a way to spatially analyze the characteristics of streets and land use in an area, through the Gini method, to discuss justice in the distribution of land uses along the streets and at the regional scale. Therefore, in the first step, the layers of streets and land uses of the Valiasr neighborhood, located in District 6 of Tehran, which have the ability to perform spatial analysis, have been collected. In the second step, in order to present the calculation model, the streets that have a length of more than 200 meters, which play higher importance in the distribution of land uses in the neighborhood, are selected and form the layer of analysis. As a result, the type and number of land uses in every section of the length of a street will be identified linearly and included in the final analysis. In the third and final step, using the concept and equations of the Gini index, the amount of equality in the distribution of land uses in each street is calculated by dividing each street into equal deciles. The Gini index is a statistical index to measure the distribution of data among a community, which is often used to measure economic inequality, or in other words, how wealth is distributed among individuals in a society. In the field of urban planning, the Gini coefficient is used as one of the important indicators to study horizontal and vertical equity in the distribution of land uses. In the present study, the number related to the Gini index explains the uniformity in land use distribution. Finally, the average coefficients of all streets are introduced as the Gini index of the whole neighborhood. 3-Results and Discussion By examining the results of the study, it is possible to observe the difference between the Gini index of the streets according to the distribution of land uses. Besides, the increase in the Gini coefficient is consistent with how the land uses are distributed in the Valiasr neighborhood due to the lack of proper land use mix for one or both sides of a passage. The Gini coefficient of the neighborhood is calculated as 0.3, which is in a low inequality range. The comparison of the results of the present study and previous studies shows that Gini coefficient of the neighborhood is not only due to the balanced distribution of residential land uses, but also there is a good mix in the arrangement of all land uses in the passages. As a result, the ability to walk in this area will be at a high level, because the presence and distribution of different types of uses along the streets are one of the most important factors encouraging people to walk. Besides, land use mixed-ness is one of the most important factors involved in the level of accessibility in urban areas, and its increase is associated with improvement in accessibility because the high mixed-ness results in lowering the travel distance for residents leading to good accessibility. In addition, the existence of different transportation options within the neighborhood is another influential factor that has been addressed in various studies. However, the worrying point, along with the high capability of walking and access to public transportation infrastructure in the Valiasr neighborhood, is the existence of the highest frequency of traffic accidents leading to pedestrian injuries in this neighborhood. Although the desirability of pedestrian access is high due to the relatively good distribution of services in this neighborhood, the high frequency of accidents in the neighborhood can be a deterrent against walking. 4-Conclusion The findings reveal that the calculation of the Gini coefficient of the roads in an urban area can represent the level of land use mix, accessibility to land uses, and the ability to walk in that area. This index can be used along with other parameters in more comprehensive studies and operate as an indicator of justice in the distribution of land uses, as well. In addition, it is effective in prioritizing the allocation of land uses and could be used in planning along with the land use mixed-ness index. On the other hand, the calculation of the Gini index can predict the travel behavior of individuals along with transportation indicators such as the level of accessibility to public transport infrastructure. Obviously, a higher Gini coefficient indicates the need to spend more time for traveling, and this could change the residents' travel behavior, from pedestrians and bicycles to motor vehicles. Increased use of motor vehicle modes are among the main reasons for traffic, lack of parking, air pollution, noise pollution, and also an increase in the risk of accidents for pedestrians. In general, the Gini index as a parameter of spatial equity and a subset of social justice can be utilized among other assessments, to analyze horizontal and vertical equity in cities.
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