Overview of methods for calculating the capacity of city streets

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Overview of methods for calculating the capacity of city streets

Pernebekov S.S

Аннотация

В статье рассмотрены основные методики расчета пропускной способности улично-дорожной сети города на примере города Шымкента Республики Казахстан. Так как планировочные особенности, а также геометрические параметры улично-дорожной сети населенных пунктов, особенно городов, оказывают существенное влияние на основные характеристики автотранспортных потоков, проанализированы преимущество и недостатки существующих методик расчета основных показателей пропускной способности улично-дорожной сети.

Ключевые слова: пропускная способность, улично-дорожная сеть, городские магистрали, перегоны улиц, транспортный поток, интенсивность. 

Overview of methods for calculating the capacity of city streets пропускной

Review traffic capacity network

Pernebekov S.S.1, *, Tortbayeva D.R.2, Makhanbetzhanov M.N.3

1, 2, 3 M.Auezov South Kazakhstan State University, Shymkent, Republic of Kazakhstan

* Corresponding author (saken_uko[at]mail.ru)

Abstract

The article discusses the basic methods for calculating the throughput of the city's road network using the example of the city of Shymkent of the Republic of Kazakhstan. Since the planning features, as well as the geometric parameters of the road network of settlements, especially cities, have a significant impact on the main characteristics of traffic flows, the advantages and disadvantages of existing methods for calculating the main indicators of the capacity of the road network are analyzed.

Keywords: traffic capacity, road network, city highways, street hauls, traffic flow, intensity.

For the Republic of Kazakhstan, the problem of increasing the capacity of city roads and increasing the speed of communication has acquired a nationwide scale, and its solution relates to the priorities of the state socio-economic policy. An increase in the motorization of the population of Kazakhstan to 6-10% per year led to a decrease in the average speed of traffic flows to 12-22 km/h, with an optimal 30-35 km/h. The time spent on transportation increased by 25-50%, fuel consumption increased to 25-30%, the number of road accidents increases annually and the environment worsens. The current situation has led to a decrease in the quality and reliability of the functioning of the transport systems of large cities, a decrease in the efficiency of all city services. In the context of a budget deficit, it is important to increase the effectiveness of measures to increase the throughput of city highways in the shortest possible time with minimal cash costs.

The concept of the capacity of urban highways of regulated traffic can be divided into three: normative, calculated and practical. The practical throughput can be of two types: maximum, observed on the reference area, and practical in specific road conditions.

In the same «Guidelines for the Design of City Streets and Roads» the values of the «practical» traffic capacity of streets with different widths of carriageways with gradation of speeds from 20 to 30 km/h and 50 km/h are given, which is too small for main streets. The lane capacity on two and three-lane roads ranges from 500 to 715, and on four and six-lane roads, from 1200 to 1485 powered cars per hour.

At the end of the 1950s, the Bureau of Public Roads recommended accepting the values of the practical throughput of one lane in one direction for a city two-lane road of 750 cars per hour; for a three-lane, up to 1200 cars per hour, and for a multi-lane, up to 1500 cars per hour, respectively, at speeds of about 48 km/h.

The «Highway Bandwidth Determination Guide» provides calculation formulas for determining the bandwidth of one lane, calculated by the safety distance between moving cars. The practical lane capacity is recommended to take 1,500 powered cars per hour for urban traffic conditions.

The «Construction Standards and Rules II-60-75» provide data on the largest number of homogeneous physical units of transport per hour, depending on the category of main streets and roads and the type of intersection. It is unclear why the throughput by means of transport is given, since there are no «pure» flows of only trucks or buses, especially trolleybuses (table 1).

In the latest norms of urban planning and development (Building norms and rules 2.07.01-89), as well as in the «Recommendations for the design of streets and roads of cities and rural settlements», they refused to determine the throughput, which cannot be considered appropriate, so how designers should now focus on their knowledge of bandwidth calculation. The use of various formulas of domestic or foreign authors will lead to a very large scatter in the values of the throughput of highways.

Table 1 - Тhe throughput of one lane of the carriageway of streets and roads

In the norms of design planning and development Departmental building norms 2-85 and the norms are proposed throughput capacity to receive 750-850 powered cars. In the guide to the design of city streets and roads (hereinafter referred to as the guide), it is recommended to determine pre-throughput in the same way. The capacity of the main network of streets and roads of regulated traffic is determined in the section of the stop line. The carrying capacity of the carriageway of streets and roads of regulated traffic on the stage is not determined.

G.I. Klinkovshtein, M.B. Afanasyev, L.V. Bulavina, K.L. Hoang, E.M. Lobanov, A.E. Gorev, S.A. Azemsha, V.A. Markovtsev, D.V. Rozhansky, I.N. Pugachev, M.S. Fishelson, S.M. Khrapova and others. Some researchers adhered to the guidelines and recommended defining the throughput of city highways as the intersection throughput. Others adhered to the guidelines and proposed the introduction of a reduction factor, reflecting the influence of the length of the haul and the traffic light control mode on the throughput of highways.

Various authors provide different data on the speed at which the maximum bandwidth in the middle of the haul is observed. According to S.G.Pisarev, a maximum of 1480 units are achieved at a speed of 21 km/h.

Modern studies of the throughput of city highways of the authors of the first group (E.M.Lobanova, L.V.Bulavina, A.E.Goreva, S.M.Khrapova) are based on its determination in the cross-section of the intersection stop-line, since in urban conditions the main the limiting factor for road capacity is intersections.

The traffic capacity of the carriageway is defined as the sum of the bandwidths of individual lanes. According to the Industry Road Methodology 218.2.020-2012, the term «lane group» is introduced to determine the capacity of a controlled intersection, which means one or more lanes of the approach. The throughput is determined depending on the presence of conflicts between the group flow and other flows and their traffic intensity, the width of the traffic lanes and the fraction of the effective phase duration of the total cycle duration.

The authors of the second group adhere to the guidelines and propose to determine the throughput of one lane of the multilane highway lane taking into account the influence of the regulated intersection.

M.S. Fishelson, unlike L.V. Bulavina and Yu.A. Kremenets, suggests that some cars pass the intersection without delay and spend time T, and some cars are delayed, spending additional time on braking, waiting for an enable signal and subsequent acceleration.

Determining the actual throughput is possible only on existing roads and in the prevailing traffic conditions. Actual throughput is also called practical.

A done review of literary sources on this topic allows us to identify the main parameters that determine the throughput of city highways. The first group of authors propose to determine the throughput of a stage in its most problematic section (cross-section of a stop line of an intersection) depending on the number of traffic lanes for the duration of the traffic light cycle and the duration of the resolution signal of the traffic light. The second group of authors consider the stage as an integral element of the road network and recommend that, in addition to the parameters of traffic lights, the length of the stage be taken into account.

It has been established that in conditions of dense traffic flows the length of the haul is one of the main factors determining the operation of the haul. The insufficient length of the haul is the cause of congestion in the case when it is less than the length of the zone of influence of intersections. Using existing methods for calculating the throughput leads to overestimated values of the load factor. The error in calculating the load factor of the authors of the first group is up to 40%, the authors of the second group on hauls longer than 300 meters - up to 30%.

To develop measures to increase throughput, it is necessary to establish the main factors that determine the modes of movement on the hauls of city highways.

References

асильев А.П. Управление движением на автомобильных дорогах [Текст] / А.П.Васильев, М.И.Фримштейн. - М.: Транспорт, 1979. - 296 c.

Дрю, Д. Теория транспортных потоков и управление ими [Текст] / Д.Дрю. - М.: Транспорт, 1972. - 424 с.

Клинковштейн, Г. И. Организация дорожного движения [Текст] / Г.И.Клинковштейн, М.Б.Афанасьев. - М.: Транспорт, 2001. - 247 с.

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