The road should provide convenient and safe traffic with the design speed of cars of a given carrying capacity throughout the year or the design season with the required capacity at minimal cost. The design speed and traffic safety are ensured by the correct choice of the parameters of the plan and the longitudinal profile of the road: minimum radii of horizontal and vertical curves, maximum slopes, transition curves, widening of the carriageway, slopes of bends, taking into account the emotional perception of the driver of the road.

The highway is a large complex of engineering structures. The main ones are:

· subgrade;

· road clothes;

· drainage facilities;

viaducts and bridges;

tunnels and retaining walls.

An important element of the road is its arrangement, i.e., the placement of road signs, marking, installation of fences, lighting, etc.

The strip of terrain on which roads are located is called the right of way or road strip. The width of the right of way is regulated depending on the number of lanes of the road, the height of the embankment, the depth of the excavation, the nature of the terrain and its slope.

By purpose, roads are divided into:

public roads;

· industrial roads;

· roads of local importance (access roads of the general network, industrial enterprises, construction sites, collective farms and farms, service, patrol and landfill roads).

Public roads include roads that, in the process of forming industrial, social and transport infrastructure, connect cities and towns with each other, as well as with railway stations, river and airports.

Field roads include roads that provide transport links to oil and gas facilities - fields, production bases, shift camps with cities, railway stations, river and airports (more often helicopter communication).

Field roads are subdivided into inter-field and intra-field roads. Inter-field roads include roads connecting fields with settlements, cities, industrial bases, etc., and intra-field roads connect oilfield facilities of one field.

The passage of cars of a given weight is ensured by sufficiently strong road pavement, a reliable foundation device, and the design of overpasses and bridges. Throughput is provided by the required number of lanes. Year-round operation of the road is ensured by the correct calculation and installation of a reliable system of surface and ground drainage, protection of the road from deeps, icing, snow drifts.

The road may have a different technical level, which depends on its importance in the national economy, the complexity of natural conditions, and the traffic composition. According to the classification of SNiP 2.05.02-85 "Automobile roads", roads throughout their entire length or in separate sections are divided into categories, see table. one.

Table 1

Purpose of the road	Road category	Estimated traffic intensity, units/day
Main federal roads (to connect the capital of the Russian Federation with the capitals of independent states, the capitals of republics within the Russian Federation, the administrative centers of territories and regions, as well as providing international road transport links)	I-a (motorway)	St. 14000
I-b (high-speed road)	St. 14000
II	St. 6000
Other federal roads (to connect the capitals of the republics within the Russian Federation, the administrative centers of territories and regions, as well as these cities with the nearest administrative centers of autonomous entities)	I-b (high-speed road)	St. 14000
II	St. 6000
III	St. 2000 to 6000
Republican, regional, regional roads and roads of autonomous formations	II III IV	St. 6000 to 14000 St. 2000 to 6000 St. 200 to 2000
Local roads	IV V	Over 200 up to 2000 Up to 200

The coefficients for reducing the traffic intensity of various vehicles to a passenger car should be taken according to Table. 2

table 2

Vehicle types	Reduction factor
Cars
Sidecar motorcycles	0,75
Motorcycles and mopeds	0,5
Trucks with carrying capacity, t:
	1,5
	2,5
St. fourteen	3,5
Road trains with carrying capacity, t:
	3,5
St. thirty
Notes: 1. For intermediate values ​​of the carrying capacity of vehicles, the reduction factors should be determined by interpolation. 2. The reduction factors for buses and special vehicles should be taken as for base vehicles of the corresponding load capacity. 3. The reduction coefficients for trucks and road trains should be increased by 1.2 times for rough and mountainous terrain.

Public roads are intended for the passage of vehicles with dimensions: in length of single cars up to 12 m and road trains up to 20 m, in width up to 2.5 m, in height up to 4 m for roads of categories I-IV and up to 3.8 m for roads of the 5th category. Accompaniment by a cover car is mandatory in all cases when: the width of the vehicle with a load exceeds 3.5 m; the length of the road train is more than 24 m; and by a traffic police patrol car, if: the width of the vehicle exceeds 4.0 m; the length of the road train exceeds 30.0 m.

When designing infield roads, dimensions of bridges and pavement structures, cars and road trains with axle loads up to 120 kN, at least 2.75 m wide and up to 30 m long (VSN 26-90) should be taken as calculated ones.

Field roads are also subdivided into categories according to SNiP 2.05.07-91* "Industrial transport".

Table 3

Type and general purpose of on-site and inter-site roads	Estimated traffic volume, million net tons/year, in both directions	Road category
Production, providing production links between enterprises and their individual facilities (workshops, developed peat fields and forests, warehouses, etc.) among themselves	St. 0.7 "0.35 to 0.7" 0.35	I-in II-in III-in
Service and patrol, providing the transportation of auxiliary and household goods, the passage of fire trucks, entrances to garages, auto shops, individual oil and gas wells, as well as the passage of vehicles along the lines of specialized types of industrial transport, power supply lines and other communications serving these lines:	-	IV-in

Estimated vehicle speeds for the design of infield roads are taken according to Table. 4

Table 4

Notes: 1. Before the line, the values ​​of the design speeds for on-site and quarry roads are given, after the line - for inter-site roads of industrial enterprises.

2. Estimated speeds at intersections and industrial intra-site roads, as well as on serpentines, should be halved, but taken at least 15 km / h.

When designing roads, it is necessary to provide for measures to protect the natural environment that ensure minimal disruption of the existing ecological, geological, hydrogeological and other natural conditions. When developing measures, it is necessary to take into account the careful attitude to valuable agricultural land, nature reserves, recreation areas and locations of medical institutions.

The impact of vehicle traffic (noise, vibration, gas pollution, glare from headlights) on the environment should be taken into account. The choice of the road route should be based on a comparison of options considering a wide range of interrelated technical, economic, ergonomic, aesthetic, environmental and other factors.

Road transport network is a complex of roads, vehicles and specialized enterprises. Each of the elements of this transport network, in turn, is a complex structure. So roads include the roads themselves, structures, bridges, crossing pipes, buildings of the linear maintenance service and motor transport structures, green spaces, snow protection and travel fences, fasteners, road signs and signs.

At present, the motor transport network of Russia includes more than 53 thousand km. public roads. Public roads include extra-urban roads, which are state property of the Russian Federation and are divided into:
1. Public roads that are federal property;
2. Federal roads;
3. Roads of the constituent entities of the Russian Federation, respectively related to the property of the constituent entities of the Russian Federation;

The main cargo flows pass through federal roads, which include:
one). main roads:
- connecting the capital of the Russian Federation - Moscow with the capitals of independent states, the capitals of republics within the Russian Federation, the administrative centers of territories and regions,
- providing international road transport links;
2). other roads connecting the capitals of the republics within the Russian Federation, the administrative centers of territories, regions, as well as these cities with the nearest administrative centers of autonomous entities. In the absence of a motor road from the network of federal roads to administrative centers, federal roads include motor roads from these centers to airports, sea and river ports, and railway stations.

The list of federal roads is approved by the Government of the Russian Federation on the proposal of the Ministry of Transport of the Russian Federation (Appendix 1 to this paragraph).

In addition to public roads, motor roads located in the Russian Federation are classified according to their ownership into departmental and private motor roads. Departmental and private roads include the roads of enterprises, associations, institutions and organizations, peasant (farmer) households, entrepreneurs and their associations and other organizations used by them for their technological, departmental or private needs.

List of highways(indicating the distances between settlements) for which regular intercity transportation of goods by road is carried out, is given in Appendix 2 to this paragraph.

And organizations transporting goods by road are obliged to ensure traffic safety and the safety of the road.

On highways it is prohibited:
but). the passage of vehicles whose total height with cargo exceeds the dimensions indicated on road signs;
b). transportation of goods protruding in width beyond the dimensions of vehicles established by the state standard or technical conditions, as well as goods protruding beyond the tailgate by more than 2 meters or dragging along the road;
in). passage of all types of vehicles with axle loads exceeding the norms established by state standards or indicated on road signs.

Transportation of oversized cargo can be carried out in some cases with the permission of the road authorities and the State traffic inspectorate.

Consignors and consignees are obliged to have access roads from motor roads to loading and unloading points and keep these roads in good condition, ensuring unhindered and safe movement of vehicles and their free maneuvering at any time during transportation.

Compliance of the state of roads and access roads located on the territory of the Russian Federation with the requirements of traffic safety and the safety of cargo and rolling stock is determined jointly by the relevant road authorities, motor transport enterprises or organizations and bodies of the State traffic inspectorate.

Requirements for the quality and condition of roads are regulated by the following regulatory documents:
- ODN 218 5.016-2002 Indicators and norms of environmental safety of the highway;
- GOST R 50597-93 Highways and streets. Requirements for the operational state, permissible under the conditions of ensuring road safety;
- GOST 10807-78 Road signs. General technical conditions;
- GOST 13508-74 Road markings;
- GOST 23457-86 Technical means of traffic management. Application rules;
- GOST 256S5-91 Road traffic lights. Types. Main parameters;
- GOST 26804-86 Barrier-type metal road barriers. Specifications;
- SNiP 2.O5.02-85 Highways;
- SNiP 2.07 01.89 Planning and development of urban and rural settlements;
- SNiP 3.06.03-85 Highways;
- VSN 24-88 Technical rules for the repair and maintenance of roads;
- Instruction of the Ministry of Railways of Russia No. TsP/566 Instructions for the operation of railway crossings;

According to the law roads must be maintained in accordance with the requirements of the rules for the maintenance and repair of highways. The maintenance, maintenance and supervision of technical means of regulation, road signs and markings are provided by the relevant road and communal organizations, as well as by the bodies of the State traffic inspectorate.

The road surface must provide reliable grip of the wheels and be even, without ruts and potholes. Asphalt concrete pavements must be cleaned of dust and dirt in a timely manner. Cleaning of asphalt concrete pavements within settlements, as well as at the junction of access roads or intersections with them, should be carried out with particular care. The maintenance of motor roads in winter should be carried out in accordance with the requirements of the current guidelines and instructions for the protection and cleaning of motor roads from snow and for the fight against ice on motor roads. Roads with improved surfaces must be completely cleared of snow. Drawdowns, potholes and other unevenness of the road surface, especially at the interface with artificial structures, should be eliminated first. Shoulders must be at the same level as the roadway pavement and strengthened by soil stabilization with binders or in another way, depending on the pavement of the roadway in relation to the requirements of SNiP. The resulting gullies on the roadsides must be immediately eliminated, and until they are eliminated, they must be protected by clearly visible fences.

In the winter period of operation, it is necessary, if there is a warning from the hydrometeorological service, to carry out a preventive scattering of materials that prevent the formation of ice, and with the onset of snowfall, start patrol snow removal of roads.

First of all, these measures should be carried out in the most dangerous areas: descents, small-radius curves and approaches to them at a distance of at least 100 m. within crossings at the water level and at a distance of 100 - 150 m to the crossing, in areas with limited visibility, etc.

When performing repair work on highways, road and communal organizations, in agreement with the bodies of the State traffic inspectorate, ensure the organization of traffic in the prescribed manner by placing the necessary road signs, fencing devices, installing alarms, organizing detours, etc.

Traffic rules, like any field of knowledge, has its own system of terms. In the Rules, everything is formalized, ordered and accessible. But because of the "dryness" and clarity, it is sometimes difficult to figure out how, for example, "parking" and "stop" differ. Therefore, it is necessary to analyze the basic terms so that an ordinary student of a driving school can understand everything from the very beginning. In particular, you need to understand what the road is and what it consists of.

The concept of "road"

The traffic rules of Ukraine state that an automobile road (road) is a part of the territory created for the movement of various kinds of vehicles, as well as pedestrians, together with all the structures deployed on it (viapasses, bridges, pedestrian crossings, flyovers) and means of organizing and streamlining traffic, at the same time limited in width by sidewalks or the edge of the right of way.

From the first part of the definition, it follows that a road will be considered a territory that has been specially equipped, that is, the necessary infrastructure has been created and traffic has been organized on this surface. The road can be urban, suburban, artificial, namely, an artificially created surface - an overpass, an overpass, a bridge. The road may be temporary, created for seasonal driving. Such a road is called a trench made by a grader or bulldozer in the snow. From the second part of the definition it follows that it is necessary to give definitions of such concepts: carriageway, sidewalk, roadside, dividing strip, tram tracks. It is these terms that define the elements of the road.

This is interesting!The first roads appeared as early as the 4th millennium BC. The oldest road in Europe is located in the UK and is called the Sweet Track. In Switzerland, they discovered a part of the road, which is paved with decks in 1700 BC. In a similar way, roads began to be decorated in Holland, but 200 years later. The "mother" of modern roads is considered to be a stone road almost 1 m thick, created in 312 BC. the ancient Romans.

Definition in the Rules: a carriageway is a component of a road that is intended for the movement of non-rail vehicles. There may be several carriageways on the road, and they are separated by lanes (separating lanes) among themselves.

Beginners who have just got behind the wheel mistakenly think that the road is part of the paved land on which vehicles travel. But then what is a roadway? This term refers to an asphalted section, that is, a section of the road reserved for off-rail transport.

Cars move along the roadway, which, in turn, is divided into traffic lanes. According to the SDA, a lane for traffic is a longitudinal lane with a width of at least 2.75 m on the carriageway, marked or not marked by road markings and reserved for non-rail transport. That is, only one car can drive in one lane.

Often, special road signs are used to indicate lanes, but special road signs can also be used. In combination, these selection methods are used at intersections to highlight the number of lanes on the roadway.

If there are no markings and signs, then the driver will have to independently determine the number of lanes. Section 11 of the Rules of the Road says that the driver must calculate the number of lanes for traffic, referring to the dimensions of vehicles, the width of the carriageway, the safe distance between cars. That is, the definition is made approximately, despite the fact that it is so required by traffic rules.

According to the SDA, a dividing strip is a part of the road that is allocated structurally or with the help of narrow and wide solid lines, separating neighboring carriageways. The median strip is needed to delimit traffic flows (with opposite directions) for safe driving. This element is mandatory for the motorway, since the probability of hitting the oncoming lane is minimal.

As for the selection, it can be constructive, that is, the dividing strip is made in the form of a reinforced concrete, metal and other kind of structure. In addition, the selection can be logistical, that is, using solid bars.

Do not confuse the dividing line with a double solid marking. If the interval between the solid lines matches the width of any of them, then it is a double solid line. If the distance is greater, then this is the dividing line.

The traffic rules say that you can’t stop on the dividing strip and you can’t move along it. If there is a sidewalk on the strip, then pedestrians can move along it.

A roadside is a road element marked out structurally or with the help of a solid marking line, adjacent directly to the outer edge of the carriageway, located on the same level with it and not intended as a place for the movement of cars and other vehicles, except for cases that provide for traffic rules.

The Rules also state that parking and stops can be made on the side of the road, pedestrians can walk along it, bicycles, mopeds can ride on it if there are no special paths, as well as sledges. Often, the roadside is isolated in such a way that it does not merge with the roadway, that is, it is covered with gravel, crushed stone, sand, etc. On large highways, there are markings along the edge of the carriageway to mark the shoulder. Not all roads have curbs.

The traffic rules say that a pedestrian crossing is an engineering structure or a section of the carriageway, which is intended for pedestrians so that they can cross the road. To highlight and designate pedestrian crossings, markings, special road signs and pedestrian traffic lights are used.

If the pedestrian crossing is not highlighted, then it is calculated from the intervals between signs or traffic lights. At intersections, in the absence of any signs, traffic lights and markings, the width of the sidewalk or shoulder is used.

A pedestrian crossing is called regulated if the traffic on it is regulated by a traffic light or by a traffic controller. Otherwise, the transition is called unregulated. If the traffic lights work on a yellow signal or are off, then the crossing is also unregulated.

The SDA gives the following definition of a sidewalk: a sidewalk is an integral part of the road, which is allocated for the movement of pedestrians. The sidewalk adjoins the carriageway or is separated from it by means of a lawn. In some cases, traffic and parking are allowed on the sidewalks.

The tram track is an element of the road for the movement of rail transport. It is limited in width and is distinguished either by road markings or by the pavement of a tram line. The movement of rail transport is regulated by Section 11 of the SDA.

What is a road? A road is a set of a number of elements or terms, each of which has clear boundaries, a clear definition and purpose. Any self-respecting driver should know and remember the constituent parts of the road to ensure the safest possible ride for himself, for other drivers, and for pedestrians.

The projection of the axis of the highway on a horizontal plane, with the image of the elements of relief and landscape, is called the plan of the route (the position of the axis of the highway on the ground).

The projection of the axis of the road (on the surface of the carriageway) on a vertical plane passing through the axis itself is called a longitudinal profile.

Cross slope is a term referring to a transverse profile (section by a vertical plane perpendicular to the axis of the road).

Slope - the ratio of the elevation to the foundation. A dimensionless quantity equal to the tangent of the angle between the inclined section and its horizontal projection. It is expressed in ppm ‰ (thousandths).

for small values ​​of α

In order to formulate the requirements for the geometric elements of the axis of the road, we consider the forces acting on the car during its accelerated upward movement:

- resistance to movement on the rise;

- rolling resistance (rolling friction);

- vehicle inertia;

-windage

The movement of the car is possible if the traction balance condition is met:

, where

[H] - traction force developed by the design vehicle

Appendix 03_02

The resistance to movement on the slope i, is determined by the work done by the engine to move the car per unit height. If we take the length of the section, and the excess of its end point over the initial one, then, neglecting all other forces acting on the car, the engine work will be equal to:

[kg] – vehicle weight;

We attribute the work of the engine to move the car to a height , to the length of the section , we get the value of the force necessary to overcome the slope i at each of its points:

Obviously, if the condition is not met, then the movement of the car becomes impossible. Otherwise, neglecting all other forces acting on the car, it is possible to determine the permissible value of the longitudinal slope from the condition of the possibility of movement of the calculated car:

Of course, in the case of real calculations, it is necessary to consider the totality of the action of all resistance forces. In addition, the limit values ​​obtained as a result of such a calculation are not satisfactory in terms of speed and driving comfort. Therefore, it is necessary to introduce some safety factors.

Rolling resistance is caused on a perfectly flat surface by the expenditure of energy to overcome the deformation of pneumatic tires, as well as the elastic and plastic deformations of the pavement. It is logical that the rolling resistance is the sum of the corresponding values ​​for each wheel of the car:

, where

[H] - fractions of gravity attributable to individual wheels;

– corresponding rolling resistance coefficients

Typically, the rolling resistance coefficient is related to the total weight of the car, that is, it is considered that:

Rolling resistance coefficient values ​​vary depending on the material and surface condition of the coating. For asphalt concrete and cement concrete pavements f = 0.01 - 0.02; for a dirt road with roughness f = 0.15. It is logical that the coefficient of rolling resistance, and in fact, the rolling resistance itself in real conditions is a function of evenness.

We will consider the resistance of inertial forces in the context of traction balance exclusively as the inertia of translational motion. However, do not forget that on curved sections in the plan, inertial forces will determine the level of traffic safety, but we will consider this issue separately. In addition, part of the engine power is spent on overcoming the inertia of the rotating parts, which must be taken into account when assessing the real dynamic characteristics of the car. Taking into account the above limitations, the resistance of inertial forces will be expressed by the ratio:

, where

is the relative acceleration of the vehicle;

[m/s2] – translational acceleration of the vehicle

[kg] – vehicle weight;

[m/s 2 ] – free fall acceleration

Air resistance is caused by three reasons:

-pressure of oncoming air on the front of the car;

- friction of air on the side surface of the car;

The power consumption to overcome the resistance of the turbulence of the air jets behind the car, near the wheels and under the body.

According to the laws of aerodynamics, the air resistance will be equal to:

, where

is the drag coefficient of the medium (a dimensionless quantity depending on the shape and shape of the body, as well as on the smoothness of its surface);

[kg / m 3] - air density;

[kg / m 3 ] - coefficient of air resistance, determined experimentally;

[m 2 ] - the area of ​​the projection of the car on a plane perpendicular to the direction of its movement;

[m/s] is the relative speed of the vehicle and the air.

Given the characteristics of the calculated vehicle and the value of the calculated speed, it is possible to determine the values ​​of permissible longitudinal slopes for certain driving conditions. It should be noted that the values ​​of the longitudinal slopes of the road, among other things, determine the cost of fuel during the movement of cars, and, consequently, the transport component of the cost of transportation. Therefore, it is logical to consider the appointment of longitudinal slopes also in the context of the efficiency of transport work.

On difficult sections of roads in mountainous areas, the lengths of long sections with slopes of more than 60 ‰ are limited depending on the height of the section above sea level.

The values ​​of the maximum permissible longitudinal slopes are determined by the value of the calculated speed, therefore, when determining them, the dynamic characteristics of the calculated vehicle were taken into account (power is not the same for different gears and speeds).

Appendix 03_03

"Requirements for the geometry of the road"

Next, consider the curvilinear sections in the longitudinal profile and the conditions of movement along them. In the case of movement along a convex vertical curve, an inertia force acts on the car, directed from the center of curvature.

In this case, the weight of the car (the force with which it acts on the surface of the coating) is reduced. Neglecting the value of the angle between the vectors of centrifugal force and gravity, it can be written that the weight of the car will change (decrease) by an amount equal to the value of the centrifugal force:

, where

[m/s] – vehicle speed;

[m] – vertical curve radius

By reducing the weight of the car, the value of the friction coefficient also decreases. Coefficient of adhesion: a dimensionless value equal to the ratio of the traction force on the rim of the drive wheel to the proportion of the vehicle's gravity attributable to this wheel at the time of slipping:

In fact, the coefficient of adhesion characterizes the limiting value of tractive effort, in relation to the force of gravity attributable to a given wheel. With a greater value of traction force, the connection between the surface of the coating and the wheel is lost, slipping begins. (for a/b coatings 0.5)

Assuming the coefficient of adhesion to be a constant value characterizing only the qualitative state of the pavement surface of the roadway, it is obvious that the maximum traction force (in fact, characterizing the stability of the car) decreases along with the value of the car's weight. This change is proportional to the square of the speed of movement and inversely proportional to the radius of the vertical curve. Therefore, for large values ​​of the calculated speed, from the condition of vehicle stability, it is necessary to introduce large radii of vertical curves.

In the case of a car moving along a concave vertical curve, the centrifugal force, on the contrary, leads to an increase in its weight. It is logical to assume that in this case the stability of the car increases (the maximum possible value of tractive effort increases). But at the same time, the load on the chassis of the car also increases. So, for an estimated speed of 80 km / h, when moving along a concave vertical curve with a radius of 1000 m, the value of the centrifugal force will be:

Appendix 03_04

"Requirements for the geometry of the road"

Inertial forces act on the car and when it moves on a curve in the plan (in the horizontal plane). With a certain combination of speed and radius of curvature, the vehicle may skid or roll over. Therefore, to determine the minimum allowable curve radius in the plan, one should proceed from the value of the design speed.

Consider the case of a car moving along a section of the carriageway with a transverse slope i. Let's write down the sum of the projections of all forces acting on the car, on the axis passing through its center of mass and parallel to the surface of the roadway:

Revealing the value of the centrifugal force and, taking into account the possibility of different directions of the transverse slope, we get:

In order to obtain a relative indicator that characterizes the conditions of movement on the curve in plan, independent of the mass of the car, we divide the resulting amount by the value of gravity:

The resulting coefficient is called the shear force coefficient. It shows what proportion is the sum of all the forces that tend to move the car from the curve for given combinations of radius, speed and cross-slope of the carriageway in relation to the force of gravity acting on the car. Express the value of the radius:

; ; ;

Thus, an expression was obtained to determine the permissible value of the radius of the curve in the plan at a certain value of the design speed. In this case, the driving conditions will be characterized by the coefficient of the transverse force:

-at m< 0,10 – кривая пассажирами не ощущается;

- at m = 0.20 - it is felt and the passenger experiences inconvenience;

- at m = 0.30 - the entrance from the straight section to the curve is felt as a push, tilting the passengers to the side;

- with m > 0.6 - the car may tip over.

So, for an estimated speed of 150 km/h, and a shear force coefficient of 0.15, we get the minimum allowable value of the curve radii in the plan (the transverse slope is 0):

As you can see, the cross slope of the roadway can both help and hinder the stability of cars on a curve. So, in areas where for some reason it is difficult to provide the required minimum allowable value of the radius of the curve, the roadway is given a certain transverse slope with an increase in elevation from the center of the curve. A smooth change in the transverse slope on the approaches to a curved section is called a turn. The transverse slopes of the carriageway on bends vary depending on the radii of the curves. The transition from a gable transverse profile to a single-slope should be carried out on transition curves.

Within the transition curves, there is a smooth change in radius from ∞ at the beginning to the radius of the main (circular curve) at the end. Spiral curves with a circular insert are called compound curves. Composite curves must be designed with a curvature radius of less than 3000 m on roads of technical category I and less than 2000 m for technical categories II-V. Types of transition curves: radioidal spiral, lemniscate, cubic parabola, box curves.

The value of the radius of the curve also determines the visibility distance in the plan. Thus, the minimum allowable radii of curves in the plan are determined from the condition of vehicle stability on the curve and the visibility distance.

The radii of adjacent curves in the plan should not differ by more than 1.3 times (safety factor). A short, straight insertion between two parallel-pointing horizontal curves is not recommended. With a length of less than 100 m, it is recommended to replace both curves with one, larger radius; for a length of 100 - 300 m, it is recommended to replace the direct insert of the transition curve of a larger parameter.

In addition to curved sections in the plan, certain requirements apply to straight sections. The length of straight inserts is limited depending on the technical category and type of terrain. So for a highway of the I technical category, the maximum length of a straight line in the plan is 3500 - 5000 m in a flat area.

In other words, the load, both on the chassis of the car and on the driver, increases by almost half. Under such driving conditions, the wear of the undercarriage of the car will increase markedly, and the driving comfort will deteriorate. The driver perceives such road conditions as dangerous and reduces the speed of movement, which leads to a decrease in the capacity of such sections.

The values ​​of the radii of the vertical curves determine the visibility distance in the longitudinal profile. The values ​​of visibility distances for an oncoming vehicle and for a stop are normalized separately. For the corresponding design speeds, these distances should ensure that the driver perceives suddenly emerging obstacles within the carriageway in a timely manner and maneuvers to avoid an accident (emergency braking or avoiding an obstacle). The smallest visibility distance for stopping should ensure the visibility of any objects having a height of 0.2 m or more, located in the middle of the lane, from a height of the eyes of the driver of the car 1.2 m from the surface of the carriageway.

It is quite easy to evaluate the dependence of the radii of vertical curves and visibility distances graphically. To do this, it is necessary to draw a tangent to the line reflecting the elevation marks in both directions from the viewpoint through each point of the longitudinal profile, above the line of elevation marks of the axis of the carriageway (red line). The length of the tangent segments to the touch points will reflect the corresponding visibility distance values.

Thus, the requirements for the allowable values ​​of the radii of vertical curves are determined by the following considerations:

Cars when driving at the estimated speed should not lose controllability and stability on the roadway;

The level of loads caused by inertial forces should not lead to a deterioration in the driver's emotional perception of driving conditions and wear of the vehicle chassis;

- the necessary visibility distance must be ensured.

Application 03_05

"Requirements for the geometry of the road"

Calculation of the width of one lane

The carriageway of the motor road must have a width that ensures the safe movement of vehicles at the estimated speed in one or more lanes. If the width of the carriageway is insufficient, this will necessitate a reduction in speed when cars meet. If an excessive width is assigned, then unjustified funds will be spent on the construction of an expensive coating.

The lane occupied by the width of the carriageway by a moving car is called a traffic lane. The higher the speed of movement, the greater the width of the lane is necessary for the safe movement of vehicles.

The lane width can be determined by the formula:

Then, taking the width of the car (MAZ-511) equal to 2.70 m, we get the lane width:

Transport and operational qualities of roads and city streets

Transport and operational qualities of roads

And city streets.

Lecture 1, 2

Classification of roads and city streets. Elements of roads and city streets.

1.1 Classification of roads and city streets

Highways are one of the most important parts of the country's transport system. Not a single branch of the national economy, not a single type of non-rail vehicles can function without a well-developed and reliable road network. Highways significantly affect the economic and social development of both individual regions and the country as a whole.

A highway is a complex of engineering structures (subgrade, base and pavement, bridges, etc.) intended for the movement of non-rail vehicles and pedestrians.

The term "road" refers to any road, street, alley used for traffic across its full width, including sidewalks, bike lanes, shoulders and medians.

Road network - the totality of all roads in the territory of the country, individual republics, territories, regions or districts, serving all sectors of their integrated economy. The basis for compiling the road network is the improved roads of national importance, which provide administrative, economic, cultural ties between economic regions.

Modern roads are a complex set of engineering structures that must ensure the operation of the road all year round, especially in spring and autumn, the movement of cars at any time of the day with high speeds and design loads.

All roads, depending on the purpose in the national economy and cultural life of the country, are divided into public roads and on-farm roads. Public roads are under the jurisdiction of the republic's road facilities, on-farm roads serve collective farms, state farms, access roads to them from public roads.

Public roads can be:

National significance, connecting large administrative centers, economic regions, providing links with neighboring countries;

Republican significance, connecting the capitals of the Union republics and the main administrative and cultural centers; regional (territorial) significance, connecting the capitals of autonomous regions, centers of territories and regions with district centers;

Local significance, connecting the centers of the regions with each other, with collective farms and state farms.

Depending on the national economic significance and traffic intensity, all roads are divided into five categories (Table 1).

Table 1

Traffic intensity - the number of cars and other vehicles passing through a certain section of the road per unit of time (per day or hour). Traffic intensity varies during the day and season, as well as along the length of individual sections; increases near cities, large settlements, railway stations; decreases significantly at night.

For each category of roads, certain technical standards are established, on the basis of which roads, artificial structures, and service facilities are designed and built. The standards include: the number of traffic lanes, the width of the carriageway, the smallest radii of curves in plan and longitudinal profile, the largest longitudinal slopes, etc. (GOST SNIP 2.05.02-85).

Ia - main roads of national importance, including international ones;

Ib - roads of national, republican and regional significance.

Category III includes highways of national, republican, regional and regional significance, not classified in categories Ib and II, as well as roads of local significance.

The road has been in service for many years. During this period, the parameters of the cars change. Therefore, standards have been developed for the overall dimensions of cars and the load from cars on the carriageway. Public roads of categories I-IV must provide the passage of vehicles with overall dimensions: along the length of single cars 12 m and road trains up to 20 m, in width up to 2.5 m, in height up to 4 m and up to 3.8 m for roads V category.

All elements of the road in plan, longitudinal and transverse profiles are calculated depending on the estimated speed (Table 2). This ensures the convenience and safety of movement under good road conditions.

table 2

	Estimated speed, km/h
	main	allowed on difficult sections of the road
		crossed
Notes: 1. Difficult sections of rough terrain include relief with a difference in elevations, valleys and watersheds of more than 50 m at a distance of less than 0.5 km. 2. Difficult areas of mountainous terrain are passes through mountain ranges and sections of mountain gorges.

The design speed is the maximum safety of the speed of single cars, provided by the road with good visibility and dry pavement.

When designing a road, freight turnover and traffic density are also taken into account.

Cargo turnover is an indicator of transport work in the transportation of goods, equal to the product of the mass of goods transported by the distance.

The traffic density of the road is the total mass of goods and vehicles passing along this section of the road in both directions per unit of time.

1.2 The main structural elements of the highway and their purpose

The road consists of the main elements: subgrade, pavement, artificial structures and road conditions.

earth bed- a road structure that serves as the basis for placing layers of pavement and other elements of the road. Depending on the terrain, the subgrade is designed in the form embankments- an earth massif artificially dumped from the soil above the earth's surface, having the shape of a trapezoid (Fig. 1a), and in the form notches- an earthen structure below the earth's surface, having a given shape and outline (Fig. 1b). On the slopes of the terrain, the subgrade is designed in the form half embankment-half excavation by cutting a part of the natural soil with a ledge and using it into a semi-fill.

Regardless of weather conditions and seasons, the subgrade must retain its geometric shape.

Figure 1.1 Main elements of the road:

a - in the embankment; b - in the recess;

1 - subgrade; 2 - the base of the embankment; 3 - the body of the embankment; 4 - the upper part of the subgrade (working layer); 5 - pavement; 6 - roadway; 7 - curb; 8 - sloping part of the embankment; 9 - lateral drainage ditch; 10 - sloping part of the excavation; 11 - drainage; 12 - groundwater level.

The subgrade consists of: the upper part of the subgrade (working layer); embankment bodies (with sloping parts); sloping parts of the excavation and the base of the excavation; devices for lowering or diverting groundwater (drainage); supporting and protective geotechnical devices and structures designed to protect the subgrade from dangerous geological processes (mudflows, avalanches, landslides, erosion).

Upper subgrade (working layer) is a part of the canvas, it is located in the area from the bottom of the pavement to 2/3 of the freezing depth, but not less than 1.5 from the surface of the roadway. The working layer is designed together with the design of the pavement.

Mound body subgrade is located below the working layer and is more often backfilled in areas of high embankments, using local or imported soil.

embankment base- natural soil with an undisturbed structure, on which a subgrade is being built, or an array of soil below the bulk layer; recess base- soil mass below the boundary of the working layer.

The sloping parts of the embankment or notches are lateral inclined surfaces that limit an artificially backfilled earthen structure.

The subgrade includes the drainage structures associated with it, necessary for the removal of surface water; ditches, lateral reserves, fast currents, evaporation pools.

Groundwater affects the strength and stability of the subgrade. Therefore, it is necessary to lower or intercept water by means of drainage design.

road clothes- a multilayer structure that perceives the load from vehicles and transfers it to the ground base. Pavement consists of a top layer (cover), a bottom layer (base) and additional layers.

Road structures are constantly affected by the natural conditions of the area. Changes in air humidity, daily temperature fluctuations, prevailing wind direction, snow cover height and much more significantly affect the choice of subgrade marks and pavement design. The service life of pavement depends on the strength of the construction materials.

1.3 Artificial structures and their purpose

When laying a road on the ground, one has to overcome various obstacles: streams, rivers, ravines, ditches, dry valleys, gorges, mountain ranges, existing roads and railways.

To ensure the continuous and safe movement of vehicles, artificial structures are provided: pipes, bridges, overpasses, tunnels, overpasses, viaducts, special structures on mountain roads (Fig. 1.2).

The most common types of artificial structures on roads are pipes and bridges. Pipes they are laid in the body of the subgrade on dry land or when crossing small streams (keep the embankment above the pipes). They are designed to pass small volumes of water under the road. Pipes are also used under exits and crossings. In some cases, pipes (rectangular section) are used to pass small local roads under the main road, as well as cattle passes in rural areas.

Bridge connects sections of the road located on both sides of the river, and serves to cross the water barrier, gorges, dry valleys. The bridge interrupts the subgrade of the road, and the movement of cars is carried out along the bridge structure, consisting of span structures and supports.

Tunnels used for laying a road through the thickness of a mountain range or under a water obstacle. In mountainous areas, tunnels are designed through mountain ranges or along steep slopes, in the area of ​​landslides, screes, landslides, steep mountain ledges. Underwater tunnels are being laid instead of bridges.

viaduct serves to pass cars through another road or railroad; by design, it is a kind of bridge.

Viaduct is a bridge of great height, located over a deep gorge, hollow or ravine. The viaduct through narrow gorges is designed as single-span due to expensive intermediate supports.

Rice. 1.2. The main types of artificial structures:

a - pipe; b - bridge; c - tunnel; d - overpass; e. - viaduct; e - overpass; g - gallery; h - retaining wall:

1 - round pipe, 2 - road embankment, 3 - bridge abutment, 4 - bridge span, 5 - mountain range, 6 - portal, 7 - intermediate support, 8 - prefabricated reinforced concrete wall.

Overpass erected instead of a high embankment or to pass the road over a longer length at difficult intersections of highways.

galleries arrange on mountain roads to protect against snow avalanches and rockfalls, most often located on steep slopes, in places of already known snow and stone landslides. The walls of the gallery must be strong, the upper vault must have an inclined surface towards the slope. This is necessary for the unimpeded descent of snow, ice, stones through the ceiling of the gallery.

retaining walls support the road on steep slopes in mountainous areas. They are arranged instead of subgrade slopes on steep slopes, in landslide areas, on the banks of mountain rivers, in areas of scree. Retaining walls are built of reinforced concrete, concrete and in the form of stone luggage.

1.4 Road facilities and protective road structures.

Road construction includes technical means of organizing traffic (fences, signs, markings, guiding devices, lighting networks, traffic lights, automated traffic control systems), landscaping, and small architectural forms.

Road protections are subdivided into two groups: protections of barrier and parapet types; railing type structures, meshes.

The barrier fencing consists of posts and a horizontal beam or a profile steel tape. The parapet fence is a reinforced concrete wall. These types of fences are designed to prevent the exit of vehicles from the subgrade, the carriageway of bridges, overpasses, flyovers. The height of the fences is 0.75-0.8 m, they are installed on the side of the road along the roadway.

The second group of fencing is designed for the organized movement of pedestrians and to prevent animals from entering the roadway.

For confident driving, the driver must be oriented in the direction of the road at a great distance. Therefore, on the sides of the road, guide devices are installed in the form of signal posts, pedestals with reflective elements.

To ensure traffic safety on the road and timely inform drivers and passengers, marking lines are applied and road signs are installed. Horizontal and vertical markings are applied to the road surface and support elements of bridges, overpasses, parapets, fences, curbs. Together with road signs, markings significantly improve the organization of traffic.

In order to give a picturesque view to roads of all categories, landscaping is provided. Landscaping has a snow protection and decorative purpose.

Snow-protective landscaping is a multi-row tree and shrub planting of a certain density. The design and placement of landings must correspond to the volume of snow carried to the road. Decorative landscaping consists in the picturesque arrangement of groups of trees and shrubs on the right of way or the creation of avenue plantings along the road.

1.5 Buildings and structures of road and motor transport services

In the process of designing the main elements of highways and artificial structures, much attention should be paid to the design of a traffic service system on the roads.

For the organization of work on the maintenance and repair of roads, servicing freight and passenger traffic, a road service is provided. For the road service, they design administrative buildings and structures, residential buildings for workers and employees, production bases, quarries, factories, warehouses, garages.

Drivers and passengers are on the road for several hours, so they need periodic rest and meals. To this end, motor transport service facilities are being designed on roads: recreation areas, bus pavilions, bus stations, motels, hotels, campsites, pavilions, canteens, shops, roadside cafes.

Recreation sites are performed away from the road with a good overview of the surrounding area, best of all on the edge of a forest, on the banks of a stream or lake. At such sites, parking areas, a recreation area and a sanitary and hygienic area with a garbage bin and a toilet should be provided. Car parks are also arranged near roadside eateries and shops.

With the growth of intercity and suburban passenger traffic, the creation of auto pavilions near settlements is required. The architectural design of the auto pavilion depends on local national characteristics and climatic conditions.

Bus stations (bus stations) are usually arranged in cities and large settlements for long-distance passengers.

Motels are built on the border zone of large cities, in resort areas, as well as in places that attract a large flow of tourists. The motel has a hotel complex, garages and a parking area, a gas station and a small service station.

In the summer, campsites are open for recreation of tourists and passengers - temporary bases from prefabricated houses or tents.

To service the rolling stock, gas stations, service stations, car inspection sites, and washing stations are being built.

Filling stations (gas stations) are designed to refuel cars with fuel, lubricants and some car care items. At the gas station there is a platform with a flyover for inspecting vehicles, minor repairs by the driver himself, and draining used oil. A platform with a flyover for car inspection may be located in the parking area at the recreation area.

A service station (SRT) performs maintenance and current repairs of vehicles.

All these structures are designed to maintain normal operating conditions of the road.

For the road control department, buildings of traffic police posts and traffic police checkpoints are being built. For an emergency call for technical and medical assistance in case of traffic accidents, there must be road telephones and radio transmitters.