Investigating the capacity of urban squares and factors affecting it (case study of Rasht city)

Master's thesis

Persian abstract

Today, urban squares are one of the most common types of intersections that have grown a lot around the world, especially in Iran. Therefore, the precise design and engineering of this type of intersections has a significant effect on improving their traffic performance. In the design of the squares, geometric parameters, traffic, aesthetics, etc. should be considered. paid attention One of the important traffic parameters in all types of intersections is their capacity, which indicates the maximum volume of incoming vehicles in squares. The purpose of creating squares instead of other types of intersections is to increase their capacity and reduce the delay caused to vehicles. Intersection capacity analysis models are basically divided into two parts: regression models that use data collected at the location to display the relationship and significance between them, such as the effect of geometric characteristics or the volume of circulating vehicles on the capacity of the square; and analytical models such as the acceptable passing distance model, which is based on the theory of traffic flow, which uses measured observations of drivers' behavior on site, and the result of which is the establishment of relationships between field and performance measurements such as capacity and delay. In this research, using collected data such as entrance and circulation volume, acceptable and unacceptable crossing distances, as well as the rate of pedestrian traffic from three squares in the city of Rasht, and using mathematical analysis and regression, relationships were determined to determine the capacity of these squares with regard to the effect of circulation volume, driver behavior and pedestrian traffic on their entrance volume. From the results of this research, we can point out the interval of 3.03 to 3.32 seconds for the critical crossing distance of Rasht city squares.  Also, the maximum capacity of urban squares in micro models is equal to 2400 vehicles per hour and in macro models it is equal to 2618 vehicles per hour. Microscopic models are more reliable than macroscopic models because of more reliable data.

Key words: field, capacity, critical crossing distance, regression

Chapter 1

Generalities

1-1- Introduction

Today, with the increase of vehicles, roads and types of trips, the place and necessity of using traffic engineering in macro country discussions is felt more than ever. Managers and decision-makers of urban areas, especially in big cities, are always looking for a way to improve the traffic situation of cities, and therefore they try to achieve effective and optimal methods in the field of traffic by relying on traffic and transportation sciences and using experts in this field.

With the development and expansion of cities, the need for proper access to different parts of the city is discussed, and this is why intersections occupy a major part of the urban network. Intersections as nodes in the urban network play an important role in the capacity of the network and it can be said that the capacity of an urban network has a direct relationship with the capacity of the intersections of that network. One of the most important parameters considered in the design and control of intersections is their capacity and delay. Therefore, it can be said that by increasing the capacity and reducing the delay in an intersection, the capacity of the entire urban network will also increase and we will witness smooth traffic in different parts of the city.

Nowadays, squares are considered as a type of city level intersections, and according to the research conducted in advanced and technologically advanced countries of the world, it can be said that squares will work more efficiently and safer than intersections without lights, of course, this applies as long as the square has not reached its capacity and if If the square has more demand than its original capacity, it will come out of the efficient and safe state.

Squares were first proposed by the Americans and the first square was designed by William Phelps Eno, which is known as Columbus Square [1]. From the beginning, the right of way in the fields was with incoming vehicles, which caused chaos in the fields, and also due to the large design of the field, many interference movements were performed in them, and in addition to the large space for construction, their safety was also reduced, which is why the field was later removed from the interests of the Americans until the time England enacted the right of way for circulation vehicles over incoming vehicles and guidelines for the design of modern fields. With this, in addition to making the square safer, its construction space was smaller and more efficient.Then other countries, including America, Australia and According to the laws of England, it has established guidelines for itself, which are completed day by day by conducting extensive field research.

Fields in different countries have different divisions, and most of these divisions are based on the type of vehicle and the location of the field. For example, in America, squares are divided into three types of small squares, one-lane and multi-lane. In Iran, squares are often divided into two types of interfering and progressive (modern) squares.

The discussion of the capacity of squares is also an important issue in their design, just like other urban intersections. Various factors can affect this capacity, the most important of which are the circulation and input flow rate, the flow rate of heavy vehicles, the presence of pedestrians, the behavior of drivers facing the square and also its geometrical characteristics. Therefore, experts always try to determine methods for the capacity of fields based on various engineering sciences, mathematics and statistics according to local conditions. Squares can be found at the entrance of cities, neighborhoods and residential areas. Used to calm traffic. Basically, the field can work effectively as long as it does not exceed its capacity, in such a case, the field will be disturbed and its safety will decrease. Determining the capacity and examining the factors affecting it are very important in determining the conditions and situations where the square can be considered as the most efficient way to control intersections without lights. In several countries of the world, especially in Iran and in the metropolis of Rasht, squares without lights are used to control traffic at intersections. Determining the capacity of squares and the factors affecting it, such as circulation flow rate, drivers' behavior in accepting and rejecting passing time, following time, pedestrian traffic and geometric characteristics such as the radius of the inner island, the radius of the outer island, the number of lanes around the square and at each entrance, are very important.

Estimating the performance and capacity of the squares is one of the topics discussed in the field of traffic engineering. In the analysis of fields, as a type of intersection without lights, important points should be considered. One of these important points is to use the appropriate capacity evaluation method to estimate the performance parameters of the field. Always, due to the difference in traffic conditions and the behavior of drivers in different countries of the world, it is not possible to use the methods of other countries directly in the analysis of field intersections of the country, and these methods must be calibrated if used to match the local conditions.  Recently, in the countries of America, Europe and Oceania, special attention has been paid to feasibility studies of the field and its different design methods. In this thesis, an attempt has been made to discuss the analysis and determination of the capacity of the squares without lights and to investigate the factors affecting it under the traffic conditions of the squares of the metropolis of Rasht. 1-3- Research objectives In general, the aim of this research is to determine methods for analyzing the capacity of the squares without lights of the metropolis of Rasht under the influence of various factors such as the rate of circulation, the rate of pedestrian traffic, as well as the behavior of drivers in accepting or not accepting passing distances.

Nowadays, to analyze the capacity of the fields, various micro and macro methods are used, and by using statistical analysis such as regression, models are obtained to determine the capacity of the fields. In this research, due to the lack of a unified method for analyzing the capacity of squares without lights in the country, by collecting the influencing parameters on the square capacity, both micro and macro methods have been used to determine the square capacity model, and finally, according to the evaluation and validation of the obtained models, the best method to determine the capacity of squares in Rasht city was obtained and this model was used to design the squares under construction or to change the type of intersection control.

1-4- Hypotheses

In this research, it is assumed that all drivers are homogeneous and show similar behavior when faced with the field. It is also assumed that the circulation vehicles always have the right of priority over the incoming vehicles and all the models are based on this basic assumption.