The study employs a comprehensive and multifaceted analysis to gain better vision and to analyze mobility in the historical centers of Syrian cities.
The diverse sources enable the study to better understand mobility patterns in Syrian cities, including identifying areas that suffer from traffic congestion, and identifying fac-tors that affect pedestrian and vehicular movement. Furthermore, this study will contribute in the development of effective possible strategies to improve mobility and promote sustainable urban development in historic cities.
This developed method synthesizes cluster and spatial analysis to gain a deeper understanding of mobility patterns within the historic centers of Syrian cities. By understanding and applying this method street segment scenarios can be developed that aim to improve traffic flow, reduce congestion, and make historic areas safer and more comfortable for residents.
Also, spatial analysis is based on the analysis of spatial data and the distribution of activities within historic centers. This analysis can reveal areas, these areas that are more congested as a result of the concentration of attractions and services, which can help identify where it is important to focus while improving traffic flow and minimize heavy pressure on the streets.
2.2.1. Spatial Analysis
This step focuses on a comprehensive examination of the urban movement patterns within Syrian cities, in our case with a particular focus on Aleppo. The analysis employs a Geographic Information System (GIS) to analyze the street network, which allows for a detailed classification of the street network, thus providing insight into the urban structure of the historical city center.
As shown in
Figure 1, the streets of Aleppo's historical center can be classified into the following:
Primary streets: These are the principal streets that connect Aleppo to its historic core and have been designed to accommodate vehicular traffic.
Secondary streets: are defined as those that connect the primary arteries to the inner core of the city, these streets are narrower in width.
The area surrounding the castle (living streets): The streets surrounding the castle are characterized as residential, with a width of approximately 10 meters.
Pedestrian routes (historical street): These routes are found in areas of main markets and near religious objects of heritage.
Alleys: are narrow passages that wind through the city, often leading to dead ends. They are typically found in areas with a high concentration of residential buildings. These narrow passages, increases the feeling of privacy, while giving the pedestrian a higher understanding of place soul.
By determining these distinct street types, a better understanding of historical city’s transport structure is attained, providing better vision into the city's historical evolution and spatial organization,
Figure 5 shows classification of previously mentioned streets.
In order to understand the analysis and its objectives and in order to reach results that are compatible with the current challenges, it is necessary to identify the different types of mobility used in the historical city of Aleppo, and to describe their operational characteristics.
For example, we have found that private cars are used primarily for individual mobility, where they dominate, and it also interacts with public mobility, as can be noted that the private cars and public transportation shares the same paths on the streets, which can lead to mobility problems, and despite the convenience and environmental protection provided by shared public mobility such as buses, as a service, they are considered weak and few in number in the city historical city of Aleppo, which also notable in other historical Syrian cities.
When considering the population number, it is important to note the importance of taxis as public mobility in the city, and on a more detailed level, individual movements and pedestrian paths are also considered essential components of the transportation network, especially in the historical center, that’s why the research is presented, for the purpose of developing and enhancing the pedestrian mobility network.
In order to get a better and deeper understanding, it is necessary to explore and describe the mutual relation between the various types of mobility and related aspects. This includes examining the operational capabilities, speeds, and spread of various means of transportation.
By examining the transportation network in the historical center, using open data sources provided by the Syrian central bureau of statistics, it was found that there are five main types of mobility (personal mobility, public mobility, service vehicles, personal mobility aids, and pedestrians).
Figure 6 below shows that each of the five types of transportation mentioned above has been classified into three types of registration within the country (public, private and governmental), in addition to specifying the number of registered means of transportation and the speeds allowed for each type.
Which enabled us to identify changes in the number of registered vehicles and permitted speeds within the country, and in the light of this, we can work on recommendations to enhance safety through different proposals that help determine the speeds and number of cars allowed for each territory in the city according to the types of events it contains.
2.2.2. Cluster and Spatial Analysis
Cluster analysis is one of the most powerful statistical techniques performed for the purpose of grouping a set of objects into a class of similar objects. In this case, objects in the same cluster would share a lot more similarities with each other than objects from any other cluster.
More specifically; the algorithm creates clusters, that can be formed based on a data set according to the similarities between data points, without the use of any background information on group membership [
43].
The purpose of cluster analysis is mainly to group data in a way that reveals basic patterns or structures for convenient exploration and recognition of patterns from the data. Therefore, the process of clustering, helps to provide insight into the basic structure of the dataset, something that would be useful in a whole host of activities, from data segmentation to classification [
44].
In this research, cluster analysis involves the K-means method, one of the clustering methods. It partitions the data set into K-dimension groups based on similarities in items.
This is an algorithm, which in the first place first starts with the random initialization of basic centroids for K clusters; after taking this step, each data point will then follow the nearest centroid.
The iterative re-calculation of centroids, which is based on the average data points assigned to the groups, proceeds to the next step; at each turn, the data points are reset to their nearest centroid.
This process goes on iteratively till the centroids trying to change in a basic way and reach a stable final solution [
45].
In general, and in simple words. K-means clustering is the process of minimizing the sum of squared even distances between given data points and their cluster centroids with the goal to get a well-separated and designed, clusters.
The general process of cluster analysis with k-means can be described as the following:
1. Data Selection and Normalization:
While working with the dataset, it is important to keep in mind that usually, the variables of a matrix are measured in different units and often have very different scales. Therefore, it is very necessary to give each variable an equal chance to influence the clustering result. The purpose behind this process is that the scale of these variables should be changed, to make each of their contribution equal.
Min-Max Scaling: It is a normalization technique that transforms all variables into a common scale, which will lead to maintain all the differences in the ranges of these values. This will be quite useful in some particular cases when there is a need to keep the relative relationships existing between the original main values.
The process involves rescaling the range of the values, so that all the ranges would lie in the interval [0, 1], and the formula for Min-Max scaling is as follows in formula (1):
Where:
X is the initial value;
X min - minimum value of the parameter;
X max - maximum value of the parameter.
2. The determination of the number of clusters:
The optimal number of clusters is determined by the following standards: Selecting the optimal number of clusters is a primary stage in cluster analysis, because it mainly affects the results that can be reached from the data, so the elbow method is a commonly used to ensure the optimal number of clusters in the k-means cluster method
The Elbow Method
The Elbow Method requires performing the k-means clustering algorithm on the dataset for a range of cluster numbers (usually from 1 to 10) and calculating the weighted sum of squares within the cluster (WCSS) for each, also the sum of squares within a cluster is a measure of the total variation within the clusters, and as the number of groups increases, the WCSS tends to decrease. This is can be explained by knowing that each cluster will have fewer component models, and the models will be closer to their own centers [
46].
The following formula (2) can give use the number of clusters
Where:
- WCSS(k): intra-cluster sum of squares for a given number of clusters k.
- n: the total number of data points.
- k: the number of clusters.
- xi: represents the i-th data point.
- cj: is the centroid of the j-th cluster.
- d(xi,cj) :distance between data point xi and centroid cj.
The plot of the WCSS against the number of clusters allows to get the visual inspection of a curve representing the “elbow” in the data. This curve can then be used to select the number of clusters that best represents the data set. This method is straightforward and readily applicable, demonstrating it a prevalent approach for determining the optimal number of clusters in k-means clustering.
3. Application of the K-Means algorithm:
The algorithm employs a straightforward and expedient iterative methodology to partition the dataset.
The following is a step-by-step process:
The initialization of centroids is as follows: The algorithm initiates the process by selecting a set of 'k' points from the dataset as the centroids of the clusters. The selection of these centroids may be random or based on a specific strategy designed to enhance the quality of the clusters.
The next step is the assignment of data points. Subsequently, each data point in the dataset is assigned to the nearest centroid. The Euclidean distance between the data point and the centroid is typically employed to determine the "nearest" point.
The centroids are updated as follows: when all data points have been assigned to clusters, the centroids are recalculated. This is accomplished by calculating the mean of all data points within each cluster [
44,
45,
46].
Iteration: Steps 2 and 3 are repeated iteratively until the centroids will no longer shows significant variation, indicating that the clusters are as consistent as possible.
The K-Means algorithm is designed to minimize the total sum of squared distances between the data points and their respective cluster centroids. The formula (3) is for calculating this, known as the objective function of K-Means, is as follows:
Where :
xi: represents the i-th data point.
Sj :represents the set of data points assigned to the cluster
j and cj : is the centroid of cluster j.