Schematic diagrams of the street-road network. Road network of residential areas and microdistricts

Lecture 3 (4 hours)

1. Schemes for constructing a street and road network of cities

2. Requirements for UDS, characteristics of UDS

3. #G0Classification of city streets and roads

4. Main technical parameters of roads and intersections

Literature:

1. Klinkovstein, G. I. Organization of traffic [Text]: textbook. for universities / G.I. Glinkovstein, M.B. Afanasiev. - Moscow: Transport, 2001 - 247 p.

2. Lanzberg, Yu.S. Guidelines for the design of city streets and roads [Electronic resource]. / Yu.S. Lantsberg, Yu.A. Stavnichiy. - Moscow: Stroyizdat, 1980. - Access mode: http://nashaucheba.ru/v34383/lanzberg_u.s. - Zagl. from the screen.

3. SP 42.13330.2011. Urban planning. Planning and development of urban and rural settlements. Updated edition of SNiP 2.07.01-89* [Electronic resource]. – Access mode: http://docs.cntd.ru/document/1200084712. - Zagl. from the screen.

Schemes of building a street-road network of cities.

The planning structure of cities is determined by the nature of the street-road network (UAN), which acts as the arteries of the city. Streets and roads are transport communications and ways for the movement of people. Along them, networks of water supply, sewerage, power supply, etc. are fixed. Thus, the street-road network is part of the urban area bounded by red lines and intended for traffic and pedestrians, laying various networks of engineering equipment, and placing green spaces.

Geometric schemes for constructing the UDS have a significant impact on the main indicators traffic, the possibility of organizing passenger communications and the complexity of the tasks of organizing traffic.

The following geometric schemes of the UDS are known: radial, radial-annular, rectangular, rectangular-diagonal and mixed (Fig. 1).

Figure 1 - Street network planning systems a - radial; b - radial-annular; in - fan;

g - rectangular; e - rectangular-diagonal; e - diagonal; g - free;

h - scheme of A.Kh Zilbertal

Radial the system naturally arose from a road junction. It is convenient for communication between the outskirts and the center, but does not create direct connections between the outskirts. Therefore, the radial system of highways can be preserved only in small towns. With the growth of the city, there is a need to create ring or diagonal connections between its districts, bypassing the center.

Radial-ring the system has historically developed from a junction of roads and rings of fortress walls. Being very convenient for connecting the outskirts with the center, at the same time, it has the following disadvantages in the conditions of a modern large city: it concentrates powerful traffic flows in the center, passing transit through it, limits the transport operation of radial highways with the throughput of the center; hinders communication between residential areas in the directions of the chords. Therefore, during the reconstruction of large cities with a radial-ring planning system, there is usually a need to make a number of significant adjustments to these systems - to redevelop the center by dispersing its nodes, punching new highways, reorganizing its mechanical transport networks and, in addition, creating chord highways for communication between districts of the city bypassing the center (Fig. 2).

Figure 2 - The city center of Canberra (Australia) has a system of radial and circular streets.

"Fan" the planning system is, as it were, half of the radial-annular system. From the cities that arose at the crossings over the rivers - on a higher, flood-free coast, roads fanned out. As the city grew, semicircular streets were formed - often along the fortress walls. The fan system is also found in seaside port cities located on the shores of a deep bay, and in seaside resorts, where the streets converge to the location of the park, beach, and sanatorium and medical institutions (Fig. 3).

Figure 3 - "Fan" system, plan of the city of Kostroma

Rectangular pattern characterized by the presence of parallel highways and the absence of a pronounced center. The distribution of traffic flows becomes more uniform. This scheme is found in a number of "younger" cities in our country, for example, in St. Petersburg, Novosibirsk, Rostov-on-Don, Volgograd, as well as in most US cities. Its disadvantage is the difficulty of transport links between peripheral points. To correct this shortcoming, diagonal lines are provided that connect the most remote points, and the circuit acquires a rectangular-diagonal structure (Fig. 4).

Figure 4 - Rectangular schemes: map of Rostov-on-Don, master plan of Manhattan

mixed(or combined) scheme is a combination of these four types and is essentially the most common. However, it does not have its own clear characteristics. The mixed scheme, as the name implies, lacks a clear geometric characteristic and is functionally connected, but isolated from each other, residential areas connected by roads. Such a scheme is typical, for example, for resort areas.

Diagonal(or triangular) highway layout system is rare. With its indisputable advantages (low coefficient of non-straightness and freeing the city center from excessive transit), it has a major drawback: complex highway nodes that reduce the throughput of the entire network.

Free the planning system, with its curvilinear or broken street routes, is characteristic of the plans of many cities of the Middle Ages. The high coefficient of non-straightness makes it inconvenient for large cities. Therefore, during their reconstruction, it is often necessary to break through new direct highways. However, for small towns and, in particular, for complex terrain, a rationally thought-out system of free planning may be the most acceptable form of building a network of streets. New free planning systems with skillful use of terrain features have become widespread in the construction of small cities and towns in England and the USA.

In Soviet and foreign urban planning, a wide variety of schemes for constructing a street and road network are used. Nevertheless, an analysis of the planning of various cities allows us to speak about the existence of fundamental geometric schemes, which determine the configuration and style of their main majority. Each of these schemes has its positive and negative sides.

The most common of these would include the following:

The rapid growth of automobile traffic in cities has revealed a discrepancy between the planning and technical specifications outdated network of city streets to modern transport requirements.

Thus, practice has shown that in old cities, private entrances and exits from microdistricts to the main streets form a dense network of intersections, which significantly reduces the intensity, speed and safety of traffic.

In this regard, when planning new cities, it is recommended to apply the principle of successive junction of one category of streets to another (the principle of “tree” or “river”). Its essence lies in the fact that each transport junction must be formed either by equal categories of streets, or by streets that differ by only one category in the sequence: entrance-\u003e passage -\u003e residential street -\u003e main street of district significance -\u003e main street of urban significance –> city road (Fig. 4.3.).

In any case, the compositional scheme of the road network should not be based on formal considerations. It should be determined by the specific conditions of the area, meeting the requirements of the architectural and planning idea of ​​building a city.

In general, when assessing the outline of city highways, one can be guided by such a generalized indicator as the density of the street network, which is determined by the ratio of the total length of streets (km) to the area of ​​the city (km 2).

Transport is a special branch of material production that deals with the movement of goods and passengers. Urban transport - set Vehicle and devices that provide cargo and passenger transportation within the city. Elements urban transport:

rolling stock, road network and other transport corridors; buildings and structures of service and repair and maintenance of rolling stock and roads.

The road network is formed as a continuous system, taking into account the functional purpose of streets and roads, heavy traffic and pedestrian traffic.

The basis of the planning structure - the skeleton of the city - comp. main streets and roads. They are the framework and one of the few little changeable parameters of the urban environment. planning structure.

The structure of the UDS of the city includes:

- Trunk roads: high-speed traffic and controlled traffic

- Trunk streets

A) citywide purpose: continuous traffic and controlled traffic

B) regional significance: transport-pedestrian and pedestrian-transport

- Local streets and roads: residential street , streets and roads in research and production., industrial. and commercial warehouse zones and areas , pedestrian streets and roads , park roads , driveways , bike paths

The UDS scheme is determined by a set of urban planning tools. The most important of them are: -compact city plan; -location of city-forming enterprises; - natural features terrain; - convenience of transport service; - compositional and aesthetic considerations.

Streets and roads form a network of ground communication lines in the city plan. Main schemes of UDS:

- rectangular-diagonal scheme;

It is a development of the rectangular scheme. Includes diagonal and chord streets, punched in the existing building in the busiest directions. But there are complex intersections with flowing streets => the use of complex transport interchanges.

- radial-annular;

It is typical for large and largest cities and contains radial (they serve as a continuation highways for communication between the center and the periphery) and ring (distribution highways that ensure the transfer of transport from one radial highway to another).

- radial-semicircular(the ring does not have to close)

-line diagram;

- mixed;

- free

(typical for the old southern regions. The entire network consists of narrow curved streets with a variable width of the carriageway, often excluding car traffic. Such a scheme is unsuitable for modern cities)

AT pure form such patterns are rare. Within the district, a rectangular scheme is preserved, and as it develops, the transport system grows from a radial to a radial-ring.

Radial-ring

2. Engineering preparation of territories complicated by physical and geological processes.

Engineering training is engineering activities to transform, change and improve natural conditions, as well as on the exclusion or limitation of physical and geological processes, in their development and impact on the territory of the city. The composition of measures is established depending on the natural conditions of the territory being developed (relief, soil conditions, degree of flooding, waterlogging, etc.), taking into account the planning organization of the populated area.

But there are territories complicated by physical and geological processes, which require a special approach.

Landslides

Landslides are called movements of earth masses on slopes, arising under the action of gravity as a result of an imbalance of earth masses. According to the volume of the earth masses that have come into motion and the depth of their capture, landslides are divided into landslides, wasps and landslides proper. They occur on the slopes of the banks of rivers, seas, ravines and mountain slopes.

In urban and rural settlements located in areas prone to landslide processes, it is necessary to provide for the regulation of surface runoff, the interception of groundwater flows, the protection of the natural buttress of the landslide massif from destruction, increasing the stability of the slope by mechanical and physical and chemical means, terracing slopes, planting green spaces.

Measures to prevent the development of landslides:

Construction and other heavy materials should not be placed on the slopes and the upper edge of the slopes, as well as monumental massive structures should not be placed. When performing planning work, it is impossible to cut off large masses of soil at the base of the landslide slope, which are a natural stop (buttress).

In order to avoid dynamic loads and shaking of slopes, it is impossible to build roads for the movement of trucks along the upper edge of the slope.

The territory of landslide slopes should be used for planting trees, shrubs and adapted for walking and recreation of the population.

With insufficient sunlight and poor ventilation of shaded slopes, snow will melt slowly in the spring, which can lead to waterlogging of the slopes. In these cases, when landscaping slopes, thick planting of trees and shrubs should not be done.

To prevent the destruction of landslide slopes, preserve vegetation on them and improve them, a number of measures are taken to eliminate the causes that contribute to the occurrence of landslides. The main ones are:

a) proper organization of the runoff of rain and melt water

b) a drainage device that allows you to intercept The groundwater deep in the slope

c) proper operation of the fecal sewage network, water supply and other facilities

d) carrying out bank protection works within the coastline of rivers, seas and other water bodies;

e) creation of mechanical resistance in the way of movement of earth masses in the form of retaining walls, pile rows and other obstacles.

f) organization of permanent anti-landslide stations to monitor the state of the surface of landslide slopes and the processes occurring in their depth.

ravines

Ravines occur on the soil surface as a result of the impact of water flows on loose rocks. melt water in spring, storm water in summer systematically destroys the surface of the soil layer.

Ravines develop within the catchment area in the direction of surface runoff, i.e. from the mouth of the drainage basin to the watershed crest of the basin.

Depending on the nature of the intended use of the ravine area, a project for its improvement is drawn up. Measures to adapt the territory for urban development are reduced to preventing the growth of ravines. Shallow ravines (up to 2.2-5 m) are filled up and the resulting areas are used for urban development. With deep ravines, their areas are used for reservoirs (ponds), as well as the device for entering railway lines and roads with a convenient device for crossings and interchanges located at different levels. Steep slopes of preserved ravines are being smoothed and landscaped. In the upper reaches of shallow ravines, it is convenient to locate buildings with basements.

Karst formations

Underground waters, when meeting with readily soluble rocks (rock salt, gypsum, limestone, lomite, etc.), dissolve and leach them. Solutes are carried away with the water. As a result of this, cracks, wells, voids or caves are formed in the thickness of the earth's crust. This formation is called karst. As a result of karst formations, subsidence, dips or funnels filled with water appear on the soil surface. The nature of these formations depends on the thickness of the layer and the composition of the soils covering the rocks.

Karst areas are considered inconvenient for urban development and are used for landscaping and creating recreation areas. To protect against the penetration of surface water to rocks unstable in relation to water, drainage is arranged, and a good drainage of surface runoff is organized.

When performing work on the vertical planning of a karst territory, large cutting of the soil should not be allowed, since this will facilitate the possibility of surface water penetration into the thickness of the layer covering the karst. It is necessary to avoid the installation of structures on them, during the operation of which it will be possible for water to leak into the ground (water supply, sewerage, water tanks, ponds, etc.). The route of roads should be directed to bypass the identified border of the karst territory in order to avoid possible subsidence and failures of the road.

sat down

Mudflows are called mountain streams saturated with a large amount of clastic materials and loose rocks (mud streams). Mudflows are found in almost all mountainous regions of the country. A mudflow is formed in the upper region of a mountain river as a result of a downpour falling on steep sections of the slope, which forms water flows with a high speed of movement.

Depending on the amount and composition of the carried material, mudflows are divided into water-stone, mud and mud-stone. Such flows have the greatest destructive power.

The complex of protective measures consists of agro-mudflow reclamation work, which is carried out to reduce the size of the resulting mudflow, as well as the construction of special protective engineering structures to combat the already formed flow. Of great importance is the preservation of the grass cover, shrubs and trees growing within the mudflow basin.

To reduce the speed of flow, artificial obstacles are created by arranging transverse furrows on mountain slopes and performing slope terracing. Build protective structures - dams, dams, dams, storage tanks.

seismic phenomena

As a result of action internal forces On the Earth, movements of the earth's crust occur, which are accompanied by elastic vibrations that cause seismic phenomena - earthquakes. They are constantly observed in mountainous areas. In flat conditions, earthquakes are either not observed at all, or are very rare and their strength is 1-3 points. Areas subject to frequent earthquakes are called seismic.

By origin, earthquakes are tectonic, i.e. associated with mountain-building activity (90%), volcanic and landslide, arising from the collapse of voids that appeared during the formation of karst. The source of an earthquake is called the hypocenter. The point on the earth's surface above the center of an earthquake is called the epicenter. The speed of propagation of seismic waves in rocks varies with the age of the rocks. At the same time, the destruction of buildings is less significant than on loose rocks. In loose rocks, weakly linked stone masses, earthquakes propagate more weakly, but at the same time they are the most destructive.

Having studied this chapter, the student must:

know

• provisions and theoretical foundations of the formation of the road network of cities;
• normative legal and normative-technical documents in the field of designing the road network of cities;
• rules for designing the road network of cities;

be able to

• generalize and systematize the main documents regulating the design and operation of the road network of cities;
• solve problems related to determining the parameters of streets and city roads;
• choose the most rational design solutions for the infrastructure of pedestrian traffic and parking;

own

• skills in working with regulations and scientific literature in the field of design and functioning of the street and road network of cities;
• skills in solving practical problems in calculating the parameters of streets and city roads.

Planning structure of the street-road network. Its main characteristics

Road network(UDS) is a complex of transport infrastructure facilities that are part of the territory of settlements and urban districts, limited by red lines and intended for the movement of vehicles and pedestrians, streamlining development and laying engineering communications (with an appropriate feasibility study), as well as providing transport and pedestrian connections of the territories of settlements and urban districts as an integral part of their communication routes; is an interconnected system of city streets and highways, each of which performs its own function of ensuring the movement of its participants and the function of access to the initial and final points of movement (objects of gravity).

The road network of cities and settlements consists of city roads, streets, avenues, squares, lanes, embankment driveways, transport engineering structures (tunnels, overpasses, underground and overhead pedestrian crossings), tram tracks, dead-end streets, driveways and entrances, parking lots and parking lots.

Planning the development of the road network of cities and towns, as well as the placement of city streets and roads should be carried out on the basis of urban design standards, land use and development rules, urban planning regulations, types of permitted use land plots and capital construction facilities, town planning plans for land plots and based on the placement of elements of the planning structure (quarters, microdistricts, other elements).

The road network of settlements should be formed in the form of a continuous hierarchically constructed system of streets, city roads and its other elements, taking into account the functional purpose of streets and roads, the intensity of transport, cycling, pedestrian and other types of traffic, the architectural and planning organization of the territory and the nature of development.

A number of requirements are imposed on the planning structure of the road network.

• 1. Rational placement of various functional urban areas and providing the shortest links between individual functional areas of the city. Within big city the time spent by residents to travel from their place of residence (dormitory areas) to their place of work (industrial and administrative regions), should not exceed 45–60 min.
• 2. Ensuring the necessary capacity of highways and transport hubs with the separation of traffic by speed and mode of transport.
• 3. The possibility of redistributing traffic flows in case of temporary difficulties in certain directions and sections.
• 4. Providing convenient access to external transport facilities (airports, bus stations) and exits to country roads.
• 5. Ensuring the safe movement of vehicles and pedestrians.

The planning structure of cities is formed taking into account natural conditions: terrain, the presence of watercourses and climate. So, for example, in northern cities a network of streets will be created, located in the direction of the prevailing winds in winter time years, providing the transfer of most of the snow through the city. In cities located on a slope, a network of streets directed from top to bottom is created - the city is ventilated: the smog is transferred down to the valley.

There are the following planning structures UDS of the city(Fig. 4.1).

• 1. free scheme typical for old cities with a disordered street and road network (Fig. 4.1, a). It is characterized by narrow, curved streets with frequent intersections, which are a serious obstacle to the organization of urban transport.
• 2. Radial scheme found in small old towns that developed as trading centers. Provides the shortest connections of peripheral regions with the center (Fig. 4.1, b). It is also typical of the road network that develops around the city center. The main disadvantages of such a scheme are the congestion of the center with transit traffic and the difficulty of communication between peripheral regions.
• 3. Radial-ring scheme represents an improved radial scheme with the addition of ring highways, which remove part of the load from the central part and provide communication between peripheral areas bypassing the central transport hub (Fig. 4.1, in). It is typical for large historical cities. In the course of the development of the city, the extra-urban tracts, which converged at the central junction, turn into radial highways, and the ring highways appear along the routes of the dismantled fortress walls and ramparts that previously encircled separate parts of the city concentrically. A classic example is Moscow.
• 4. triangular pattern has not received wide distribution, since the sharp corners formed at the intersection points of the elements of the road network create significant difficulties and inconveniences in the development and development of sites (Fig. 4.1, d). In addition, the triangular scheme does not provide convenient transport links even in the most active directions. Elements of the triangular scheme can be found in the old districts of London, Paris, Bern and other cities.
• 5. Rectangular pattern has become very widespread. It is typical for young cities (Odessa, Rostov), ​​which developed according to pre-developed plans (Figure 4.1, e). It has the following advantages over other planning structures:
  • – convenience and ease of orientation in the process of movement;
  • – significant capacity due to the presence of backup highways that disperse traffic flows;
  • – no overload of the central transport hub.

The disadvantage is the significant remoteness of oppositely located peripheral areas. In these cases, instead of moving along the hypotenuse, the traffic flow is directed along two legs.

6. Rectangular-diagonal pattern is a development of the rectangular scheme. Provides the shortest connections in the most demanded directions. While retaining the advantages of a purely rectangular scheme, it frees it from its main drawback (Fig. 4.1, e). Diagonal highways simplify the connection of peripheral areas with each other and with the center.

The disadvantage is the presence of transport hubs with many incoming streets (mutually perpendicular and diagonal highways).

7. Combined scheme preserves the advantages of some schemes and eliminates the disadvantages of others. It is typical for large and largest historically developed cities. It is a combination of the above types of circuits and, in fact, is the most common. Here, free, radial or radial-ring structures are often found in the central zones, and in new areas the road network develops according to a rectangular or rectangular-diagonal pattern.

Rice. 4.1.

a - free scheme; b- radial; in- radial-annular; G - triangular; d- rectangular; e - rectangular-diagonal

Depending on the planning structure, the loading of the city center is different. The largest number transport links through the center of the city has a radial network, since transportation is actively carried out along the radial streets in the diametrical direction. The radial-ring scheme largely eliminates this drawback, since the peripheral ones go along the ring streets to bypass the center. This disadvantage is also eliminated by the rectangular scheme, which allows dispersing traffic flows along parallel streets.

UDS is characterized by the following indicators.

1. Network density of streets and roads defined as the ratio of the length of roads to the area of ​​the territory, km/km2

Sometimes the indicator is used specific gravity network, expressed in km2 of the area of ​​the carriageway of roads divided by km2 of the urban area (km2/km2).

According to modern standards, the average density of main streets 5 = 2.2-2.4 km/km2 with a distance between them of 0.5-1.0 km.

Rational distance between main streets on which traffic is carried out public transport, is assigned from the condition of convenience for city residents, so that the distance from the most remote point of the place of residence or work to the bus stop does not exceed 400–500 m.

With the same distance between the streets, the density of the network with a radial-annular planning structure is 1.5 times higher than with a rectangular scheme. The high density of the network provides the minimum length of pedestrian access to the main streets, but has such serious disadvantages as high capital investment in the network and its operation, as well as low speeds traffic due to frequent intersections in the same level.

The average density of the street network in St. Petersburg is 4.0-5.5 km/km2, including the density of the network of main streets and roads with controlled traffic - 2.5-3.5 km/km2, the density of the network of urban express roads and highways continuous movement - 0.4 km/km2.

The road network density in Moscow is 4.4 km/km2. AT major cities In the world, the WDN density is higher: in London - 9.3, in New York - 12.4, in Paris - 15.0 km/km2.

There is a relationship between the population in the city and the density of the road network. In small towns (with a population of 100–250 thousand inhabitants), the density of the SDR 6 = 1.6–2.2 km/km2, in cities with a population of more than 2 million inhabitants δ = 2.4–3.2 km/km2.

The larger the city, the greater the density of the road network and the greater the length of the streets per inhabitant. In large cities of Russia, per inhabitant, there is the following amount of UDS area, m2: in Moscow - 12, in St. Petersburg - 10, in US cities: New York - 32, Los Angeles - 105.

2. Non-straightness index is characterized by the value of the coefficient of non-straightness, equal to the ratio of the actual path that the car passes along the road network from the starting point A to the end point of the route B, to the air distance between these points:

The coefficient of non-straightness largely depends on the planning structure of the road network and the adopted organization of traffic (primarily the volume of one-way traffic).

The coefficient of non-straightness varies from 1.1 to 1.4. The smallest coefficient of non-linearity has a radial-ring scheme, the largest - a rectangular one.

3. Bandwidth road network is determined by the maximum number of cars passing through the cross section per unit of time - hour.

The throughput of the road network depends on the level of loading of individual highways, the way traffic is regulated at intersections, specific gravity highways of continuous traffic, the composition of the traffic flow, the state of coverage and other reasons.

Throughput at the same density of the UDS of rectangular and rectangular-diagonal schemes is higher than others - due to the presence of parallel alternate streets.

4. Degree of difficulty of highway crossings characterized by the configuration of the intersections of the main streets.

The most rational, as experience shows, is the intersection of two main streets at a right angle. The presence of five or more converging directions in the node significantly complicates the organization of traffic, forcing the use of ring schemes that require large areas, or expensive interchanges at different levels. Crossings of main streets at an acute angle also complicate the organization of traffic and pedestrians.

5. Loading level of the central transport hub depends on the planning structure of the loading of the city center.

The radial network has the largest number of transport links through the city center, since transportation is actively carried out along the radial streets in the diametrical direction. The radial-ring scheme largely eliminates this disadvantage, since peripheral flows are carried out along the ring streets to bypass the center.

The rectangular scheme is devoid of this drawback, which allows dispersing traffic flows along parallel streets.

• SP 42.13330.2011 "Urban planning. Planning and development of urban and rural settlements". Updated edition of SNiP 2.07.01–89*.

The transport planning of cities and the outline of the street and road network is the urban framework of cities and determines their architectural appearance.

The formation of the transport network of the city is mainly determined by its historical development. Depending on the outline of the main-street network, the following planning schemes of cities are distinguished:

- rectangular (Fig. 10, c) the scheme is typical for modern cities with planned development. Its feature is the absence of a strictly defined center and the even distribution of passenger and transport flows in all areas. Many US cities have such a transport scheme. Possessing indisputable advantages in terms of the convenience of building corner sections and the presence of duplicate directions, it is also characterized by a significant drawback: the distance between two points of a transport line located on more than one highway is much greater than the shortest distance along an air straight line. The relation of these greatnesses is called coefficient of non-straightness

- triangular(Fig. 10e) When reconstructing cities with a rectangular transport scheme often there is a need to punch diagonal lines. With a large number of diagonal streets, the scheme from a rectangular one turns into a triangular one with complex intersection nodes.

- radial(Fig. 10, a) This scheme is typical for old cities, the development of which began at the intersection of important trade routes. This scheme provides the shortest connection between peripheral areas and the city center, but at the same time, it makes it difficult for remote peripheral areas to communicate with each other. This leads to traffic congestion in the central core of the city. The radial scheme is characterized by an even greater coefficient of non-straightness compared to the rectangular scheme. As the territory of the city grows and the transport network develops, this scheme can turn into a radial-circular one. (Kharkov, Tashkent, Riga, etc.).

- radial-annular(fig.10,c) the scheme developed in old cities located at the intersection of important trade routes and having a system of ring fortifications around the center. This scheme provides a fairly convenient connection between remote areas of the city with the center - along radial directions and among themselves - along ring directions. However, radial directions, compared to circular ones, are overloaded with passenger and traffic flows, which also leads to a glut of the city center with transport;

- rectangular - diagonal(Fig. 10d) - typical for many old cities with planned development relative to the historical center. It has the same advantages and disadvantages as the radial-ring scheme, but at the same time it is characterized by a more even distribution of transport and passenger flows throughout the city;

- free(Fig. 10, f) the scheme is found in some old European and Asian cities, preserves the medieval layout and is distinguished by rather complex transport links between the regions.

Each real city is a combination of different schemes in various places, dogma should not be applied, it is necessary to look for optimal solutions. For this reason, it is often used combined schemes.

The street and road network of cities is designed as a continuous system, taking into account the functional purpose of streets and roads, the intensity of transport and pedestrian traffic, architectural and urban planning solutions of the territory.

In large cities with radial, radial-ring and rectangular-diagonal street and road networks, they try to minimize the volume of ground transport through the territory of the historical core of the city center by constructing bypass main streets, as well as long deep-laid motor transport tunnels (underground highways) under the city center .

At the intersections of main streets and citywide roads, complete and incomplete junctions are arranged at different levels*. For this, road and pedestrian tunnels can be used.

Fig. 29 Schemes of transport networks: a - radial; b - radial - annular; c - rectangular; g - rectangular-diagonal; e - triangular; e is free.