Integral elements road network are intersections and junctions of roads in the same level.
intersections and junctions, highways at the same level, they are designed on roads of category I-b with roads of categories IV, V, with the obligatory driving off of left-turn directions of traffic. On roads II, III, IV categories with a total prospective intensity in the node from 2000 to 8000 pref. units/day apply intersection patterns at the same level with guide islands on the main and secondary roads and a lane for left-turn traffic on the main road in the general road network.
Simple junctions and intersections at the same level should be designed on roads of IV, V categories with a total traffic intensity of less than 2000 pref. units/day
1 General provisions for the design of intersections and junctions in
one level.
A road intersection is a junction where several roads converge. The main requirements for intersecting roads are to ensure traffic safety with the least loss of time within the intersection. Crossings and junctions, roads in the same level are recommended to be performed at a right angle or close to it.
Timely visibility of the intersection from all entrances is necessary for rebuilding, turning, for the release of vehicles with the right of way, braking. It is achieved by the location of the intersection on sections of concave vertical curves of intersecting roads, clear information using signs. Knots with extensions are arranged to increase throughput and speed on the main road. Crossing lanes allow you to increase the width of the carriageway gradually at turning ramps. Knots with guide islands are widely used. The outline of the location of the islands is determined by the traffic pattern. Intersections and junctions of roads at the same level should be located on rectangular sections of intersecting roads in free areas. Longitudinal slopes of roads on the approaches to the intersection over the estimated visibility distances, depending on the estimated speed, should not exceed 40 ‰. At the intersections of highways, the traffic intensity is equal to the sum of the intensity of the intersecting roads. When cars move on the intersection section, interference is created when turning individual cars: 16 intersection points, 8 branch points and 8 traffic mergers. At these points, called dangerous, a collision of cars is possible. The greater the intensity at the intersection, the higher the risk of collision between cars.
Figure 1.1 - Vehicle trajectories at intersections in one level
When choosing the type of intersections and junctions in one level, a standard project 503-0-51.89 "Intersections and junctions, roads in one level" is used.
2 Types of intersections and junctions, roads in one level
Crossings and junctions in one level can be canalized, simple and circular.
The choice of the type of intersections and junctions in one level is made taking into account the categories of roads suitable for the corner, the total prospective traffic intensity, the presence of free territory, the distribution of traffic between the straight direction, left and right turns.
Traffic safety is ensured by the visibility of the intersection area, good visibility. The visibility distance is provided for the corresponding category of the crossed road. On intersecting roads, vertical convex curves are not recommended, as this reduces the visibility of the intersection.
Ring junction crossings are used when the intensity of traffic on intersecting roads differs by no more than 20%, and for left-turning vehicles by less than 40%.
Road crossings in one level
At the confluence of two or more roads, a zone of interaction between traffic flows is formed, which is called node . Such road junctions, especially if they are arranged on the same level with each other or with railways, are distinguished by the fact that they are busier than the rest of their length, since the traffic intensity at such junctions is equal to the sum of the intensities of the connecting roads. Road junctions in one level are divided into intersections and junctions.
intersection is a junction at which more than three highways converge, which, as a rule, are not interrupted, and through traffic is possible along each of them or movement with the help of special devices (ring).
adjoining - this is a road junction where another road adjoins one (in one or different levels) that has no direct continuation and terminates at this node.
At intersections, the traffic conditions for cars following straight lines are complicated by the maneuvers of turning cars. Possible trajectories of movement at the intersection in one level (Fig. 10.1) form 16 points of intersection and eight points of branching and merging of flows. At these points, called conflict , high probability of collision of cars.
Rice. 10.1. places of intersection and
confluence of traffic flows
at the intersection in one level:
1 - points of separation of traffic flows;
2 - points of confluence of traffic flows;
3 - points of intersection of traffic flows
The greater the intensity of traffic on intersecting roads and the higher the proportion of vehicles making cornering maneuvers, especially the left, the greater the mutual interference for traffic. Therefore, at a very high total traffic intensity, intersections are arranged at different levels, and at a slightly lower one, intersections and junctions at the same level, equipped with additional elements that provide a clear organization of traffic in different directions - additional transitional speed lanes and guide islands.
In accordance with the norms of Russia, at one level, it is allowed to arrange intersections of roads of category II with roads of categories IV and V, as well as roads of categories III, IV and V with each other, if the prospective total traffic intensity in the junction does not exceed 4000 vehicles / day.
The most effective measure to improve traffic conditions at intersections in one level is traffic channeling allocation for each direction of an independent lane on the carriageway. Canalization of traffic can be carried out in a number of ways - by installing guide islands on the roadway, allocating additional lanes for cars to wait for the possibility of making left turns without interfering with cars moving in the forward direction, by installing additional transitional speed lanes on the roadway for smooth braking or picking up speed by turning cars. Depending on the traffic intensity and the category of intersecting roads, islands are arranged either only on secondary roads, or on both roads (Fig. 10.2).
Rice. 10.2. Crossing and junction of roads with canalized traffic:
1 - drop-shaped islets; 2 - triangular islands; 3 marking lines on the carriageway; 4 additional lane of the carriageway for
cars waiting for a left turn; 5 - an island blocking the entrance to an additional lane
More advanced in terms of organization and traffic safety are roundabouts . The movement of cars along the ring in one direction provides a clear organization and gives it order, since all the maneuvers of cars come down to inclusion in the traffic flow and exit from it (Fig. 10.3). Roundabouts have the disadvantage that due to the continuous regrouping of vehicles, the speed of movement is significantly reduced compared to the approaches to the intersection, and the intersections themselves require the allocation of a large area. The section of the ring between intersecting roads (Fig. 10.3) must be long enough to enable cars to enter the stream and exit it in the right direction.
Rice. 10.3. Roundabout elements:
1 and 4 - approaches to the crossing;
2 - the width of the carriageway at the intersection;
3 - entry;
5 - departure;
6 - the length of the section between the guide islands;
7 - intersection;
8 - guide islands;
9 - central island
It should be borne in mind that on the section of roads adjacent to the intersection, carriageway broaden, arranging additional lanes of the carriageway on it, separated from the main carriageway by marking lines, and sometimes by additional dividing strips. These extra bands are called transitional speed . Their length ( L in meters) are assigned from the condition of acceleration and deceleration of cars from the speed on the main road to the speed when performing the maneuver (about 20 km/h):
where a- vehicle acceleration. Based on observations of the modes of motion, it is taken equal to 0.8-1.2 m/s 2 during acceleration, 1.75-2.5 m/s 2 during deceleration.
Railway crossings are a special case.
The norms provide that during new construction on roads of categories I-III, intersections at different levels must be arranged. On roads of IV and V categories, crossings at different levels are necessary in the following cases:
when moving by rail trains at a speed of more than 120 km / h;
in cases where the railway is located in a recess;
when three or more railway tracks intersect;
in suburban areas, when trolleybus traffic is provided for on the road, or tram tracks are located on the side of the road.
At intersections with railways at the same level, visibility must be ensured, in which the driver, who is at a distance from the crossing equal to the calculated visibility distance, can see the approaching train at least 400 meters away, and the locomotive driver must see the middle of the crossing 1 km away ( Fig. 10.4).
Rice. 10.4. Visibility requirements at intersections of motorways and
railways:
1 line limiting the zone of visibility of the crossing by the locomotive driver;
2 - the same as the driver of the car;
3 - cuts to ensure the visibility of the crossing
10.2. Road crossings at different levels
With high traffic intensity, ensuring uninterrupted and safe traffic in transport hubs can be achieved by arranging transport interchanges at different levels. Such junctions are arranged at the intersections of roads of category I with roads of all categories, I, II and III categories among themselves, if the total prospective traffic intensity exceeds 8000 vehicles per day.
At junctions at different levels, one of the main intersecting roads passes over the other via an overpass. Usually this is a road with less traffic. This solution makes it possible to pass traffic flows on both roads in the forward direction without slowing down due to interference from turning cars.
Moreover, right turns at intersections at different levels are carried out without hindrance, with a small decrease in speed along the so-called right turn ramps , on which traffic interference may occur when turning cars are included in the traffic flow on the crossed road. The main difficulties that give rise to a variety of intersection patterns at different levels are caused by the complexity of left turns, which can be done in one of three ways (Fig. 10.5).
Rice. 10.5. Schemes for making left turns at intersections at different levels:
awith the help of a right turn by 270 0 after passing the bridge; binon special left-turn exits
On highways with high traffic intensity, reaching several hundred thousand cars per day, the interference from speed reduction by turning cars and the danger of congestion at right- and left-turn exits are so great that their planning schemes are designed individually, taking into account the intensity of flows in different directions, providing the opportunity making left turns with high traffic intensity in the shortest direction without slowing down. As a result, intersections in three or four levels are obtained with the construction of expensive multi-tier overpasses.
On highways with a traffic intensity of several tens of thousands of vehicles per day, simpler intersections are being designed. The most common of them are shown in Fig. 10.6.
Rice. 10.6. Crossing schemes at different levels by type:
a- "clover leaf"; b- linear; in- along the distribution ring; G- rhombus
In order to reduce the size of intersections that occupy sufficiently large areas and have a large length of transition lanes and ramps, lower values of design speeds and other parameters used in the design of intersections are allowed, which, in accordance with Russian standards, are presented in Table. 10.1.
T a b l e 10.1
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Intersection characteristics |
Parameter values for road categories |
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Estimated speed at exits, km/h: |
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left-handed; |
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right-handed; |
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Longitudinal slope at ramps, ‰ |
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The smallest radii of curves in the plan at the exits, m: |
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left-turn type "cloverleaf"; |
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right-handed; |
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The smallest radii of vertical curves at intersections, m: |
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convex; |
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concave; |
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1.doc
MINISTRY OF EDUCATION OF THE REPUBLIC OF BELARUSBELARUSIAN NATIONAL TECHNICAL UNIVERSITY
INTERSECTION DESIGN
ROADS
MINSK 2007
1. Classification of road intersections
With engineering communications…………………………………………….
2. General provisions for the design of intersections and junctions
Highways……………………………………………………………..
3. Types of intersections and junctions of highways in one level………
4. Design of intersections and junctions of highways
In one level ………………………………………………………………..
4.1. General requirements for the design of intersections and junctions ………….
4.2. Plan design and simple intersection(adjacent)………………...
4.2.1. Breakdown of conjugation of the edges of the carriageway along circular curves……….
4.2.2. Conjugation of the edges of the roadway along box curves………………..
4.2.3. Conjugation of the edges of the carriageway along transitional and circular curves.
4.3. Design of canalized intersections
With guide islands, additional strips……………….
4.3.1. Additional lanes………………………………………………………...
4.3.2. Design of drop-shaped guide islands …………………...
4.3.3.Designing triangular guide islands……………………..
Design of sewer connections with guides
Transport interchanges………………………………………………………………
Elements of transport interchanges………………………………………………..
Justification of the length of transition curves in sections
Designing a “full cloverleaf” traffic interchange………….
8.1.1. Designing a plan for left-turn connecting branches ... ..
8.1.2. Design of the longitudinal profile of left-handed
Connecting branches…………………………………………………
8.2. Breakdown of left-turn connecting branches………………………
8.2.1. Breakdown of left-turn connecting branches
Rectangular coordinate method……………………………………………
8.2.2. Breakdown of left-turn connecting branches
By the method of angular serifs…………………………………………………………..
Design of right-turn connecting branches……………
Designing a plan for right-hand connecting branches ... ..
Design of longitudinal and transverse profiles
Breakdown of right-turn connecting branches…………………….
Design of incomplete transport interchanges……………………………….
With three left-hand connecting branches……………………
9.1.1. Design of an incomplete right-turn connecting
Branches……………………………………………………………………………
9.1.2. Design of an incomplete left-turn
Connecting branch…………………………………………………….
Design of an interchange "incomplete cloverleaf"
9.2.1. Design of modernized right-turn
Connecting branches of MPPO…………………………………………
Design of a traffic interchange with one left turn
Features of designing a road interchange of the "rhombus" type…………
Features of transport design
Road signs …………………………………………………………………..
Placement of road signs at traffic intersections …………………..
Design of road signs……………………………………………..
Road markings……………………………………………………………………
Vertical marking………………………………………………………….
Designing horizontal markings in the zone
Road barriers and protective devices……………………………………
Designing barrier road barriers………………………….
Conditions for the use of barrier fences……………………………..
The choice of design of the working section of the barrier fences………….
The design of the initial and final sections
Design of fences on the approaches to the overpass………………..
Design of fences in the branching zone and
Design of fencing supports of the overpass…………………………
Determining the scope of work on the device
13.2.8. An example of designing one-sided barrier
Metal fencing……………………………………………………
Classification of road intersections
Motor roads can cross the following linear engineering objects: motor roads, railways; communication and power lines (overhead and underground); pipelines for various purposes.
In addition, crossings of pedestrians, crossings of cars on crawler, from highways, exits to adjacent territories (in a field, to a forest, to a farm), entrances to courtyards can be arranged when roads of low categories are laid in settlements.
Intersections of highways between themselves and adjoining one road to another can be carried out at one level and at different levels. Intersections of roads and their junctions at different levels are called traffic interchanges (nodes), and at one level - intersections of highways, junctions of highways.
Transport interchanges should be provided, as a rule, in the following cases:
on motorways ( category I-a) and expressways ( category I-b) at the intersection with motor roads of all categories;
on automobile roads I-in categories with roads, the estimated intensity on which exceeds 1000 vehicles / day;
on highways I-in category with the number of lanes of 6 or more with motor roads of all categories at the intersection of roads of II - III categories with each other with a prospective traffic intensity (in total for both roads) of more than 12,000 vehicles / day.
Intersections of roads with railways can be designed at different levels or at one level. Highways of I - III categories always intersect at different levels, and IV and V categories when crossing the section railway with high-speed traffic (over 120 km / h) or with a traffic intensity of more than 100 trains per day, as well as in cases where visibility standards are not provided and with an estimated traffic intensity on the highway of more than 1000 vehicles / day.
Pedestrian crossings over motor roads of category Ia are designed at different levels (aerial or underground). In the case of a category Ia road, always, in the case of a category Ib and II road with a pedestrian traffic intensity of 100 people / h, for a category Ib road and 250 people / h for a category II road.
^ 2. General provisions for the design of intersections and junctions of highways
Highway - a complex of engineering structures (roadbed, bridges, overpasses) designed for convenient and safe movement road transport with set speeds and loads.
Based on the requirements for the road to road intersections, traffic interchanges, as one of the complex engineering structures of the road, are required to ensure safe and convenient traffic with the least loss of time.
^ Safety and ease of movement provided timely visibility, good visibility, clarity and ease of passage of intersections, road junctions, transport interchanges.
^ Timely visibility intersections and junctions is necessary for changing lanes, braking, turning or crossing the road, for passing Vehicle with priority right of way.
Good visibility intersection allows the driver to assess the traffic situation at the intersection and make the right decision about the traffic mode.
Clarity intersections, junctions of motor roads is provided:
installation of road signs;
roadway markings.
At the intersection of two-lane roads, the possible trajectories of the movement of cars form (Fig. 2.1) 8 points of branching of flows (1), 8 points (2) of confluence and 16 points of intersection of flows (3). At the junction (Fig. 2.2), the number of such points is 3 for each species. Points of branching, confluence and intersection of streams are called dangerous.
Traffic safety at intersections, junctions, road junctions depends on the number of dangerous points, their type, traffic intensity and direction of flows approaching dangerous points and is determined by the degree of danger G:
G = ∑N i 1, σ i N i 2 10 -3 (2.1)
where n is the number of dangerous points;
N i 1, N i 2 - the intensity of the movement of flows suitable for a given point i;
σ i - relative danger of the considered dangerous point, the largest for
Intersection points and smallest for branch points.
With a dispersed location of dangerous points, the value of σ i in Hungary is taken equal to 2 for branching points, 4 for merging points. At the points of intersection of the flows at an angle of 30 o, 60 o, 90 o, 120 o and 150 o, the values of σ i are taken, respectively, 6, 8, 12, 14 and 18.
From formula (2.1) it follows that the degree of danger largely depends on the intensity of the movement of flows that approach dangerous intersection points. Therefore, on roads with high traffic intensity, instead of intersections (junctions) of roads in the same level, transport interchanges are designed.
R
is. 2.1. Points of branching (1), merging (2) and intersection (3) of the motion trajectories
Cars at the intersection of two-lane roads. 