WO2012007796A1

WO2012007796A1 - Road interchange

Info

Publication number: WO2012007796A1
Application number: PCT/IB2010/053339
Authority: WO
Inventors: Gianmaria De Stavola
Original assignee: Idroesse Infrastrutture Spa
Priority date: 2010-07-15
Filing date: 2010-07-22
Publication date: 2012-01-19
Also published as: ITPD20100224A1

Abstract

This is a road intersection comprising three or more intersecting roads (A, B, C, D, E) with both directions of travel, and comprising two roundabouts (1, 2), each of which are accessed by one or more lanes of two or more of said roads (A, B, C, D), wherein said roundabouts (1, 2) are substantially concentric and lying on planes at different heights, and wherein the first roundabout, or lower roundabout (1) lies on a plane at a lower height, and the second roundabout, or upper roundabout (2) lies on a plane at a higher height.

Description

ROAD INTERCHANGE

DESCRIPTION

This patent is related to road intersections with roundabouts and in particular it concerns a new road intersection with at least two substantially concentric roundabouts at different levels, one at a lower level, external, another at an upper level, internal, for roads with high traffic flow.

It is a kind of configuration that takes into account:

- the space available,

- traffic flows on main arterial roads,

- the expected level of service,

- traffic conditions on a road design with different levels.

This patent refers to three, four or more arm intersections, the arms of which intersect generating high traffic flow, to be managed, therefore, with intersections that take into account costs and available space.

Below there are examples of known types of intersections which are compared based on the importance assigned to different parameters, in particular: the area taken up, the capacity, safety and costs.

Cloverleaf intersections involve two major roads.

A cloverleaf configuration requires a significant footprint area: with the same radius of planimetric curvature it occupies all quadrants in which the main roads divide the territory.

The cloverleaf configuration generates irregularities in speed in the main roadways and consequently decreases traffic safety because of the exchange areas. Cloverleaf interchanges are inexpensive because the increased use of space is offset by the construction of a single structure, namely the main flyover of a main road.

The main advantages of a cloverleaf intersection are:

- the need for a single structure; and

- the fact that each of the twelve possible manoeuvres can be completed without stopping traffic.

In contrast the negative aspects are:

- the need for a larger area than other types of intersections;

- the limitation of the capacity to exchange traffic flows between the main roads because of the existence of exchange areas in which vehicles exiting the roadway must merge with the lanes of vehicles entering the roadway, thus slowing down the traffic flow.

This limitation depends on the length of the exchange area and the number of lanes that exchange; the length is usually limited to 200-300 m, that is, at a length that creates the need to limit the entry and exit to one lane.

One entry lane, altered by the manoeuvres of vehicles exiting the roadway with the right of way in the exchange manoeuvre, limits the exchange capacity to roughly 1,000 vehicles/hour for each ramp.

Exchange manoeuvres occur at the speed of the right lane of the main roadway and can create dangerous sudden slowdowns.

Intersection solutions without exchange areas, where each ramp is independent from the others are known. Configurations with no exchange areas have no capacity constraints given that their characteristic is to be able to calibrate the number of lanes on the ramps so as to comply with the values of the exchanged flows.

In this case ramps can be constructed with more than one lane, depending on the flow, and the capacity of the lanes themselves, not being limited by exchange areas, is not affected.

The advantages of this solution are:

- there are no capacity constraints;

- there are no exchange manoeuvres between flows, only junctions;

- the number of lanes is unlimited;

- ramps are direct or semi-direct therefore loops or turns at 270° causing slowdowns are avoided.

The disadvantages are:

- needs more structures;

- the development of ramps and supporting structures is greater than for other configurations;

- requires a very large area;

- the visual impact is significant.

In contrast, with respect to the most popular intersection solutions, even applied to urban intersections, the first choice is represented by traffic lights, that is, a light signal placed at road intersections, pedestrian crossings and other locations where traffic control is needed.

Traffic lights coordinate traffic through the use of universally used optical signals consisting of colours: green to circulate, yellow for circulate with caution and red to stop. Intersections governed by traffic lights have advantages in that they:

- use a small space;

- are a low cost solution, apart from the system;

- allow pedestrians and citizens in general to cross the street safely during downtime;

- serve to organize the flow of traffic.

In contrast the disadvantages include:

- no possibility of reversing the direction of travel,

- low flow capacity,

- maintenance costs,

- waiting time for road users (stop and go).

To reduce waiting times at some intersections the traffic lights are replaced with roundabouts.

The structure of the roundabout of a known type (Fig. 1) is thus taken into account, which comprises an intersection between two or more main roads, resulting in four roads where the intersection between them is replaced by a one-way loop road around a central island.

The traffic must slow down before entering the roundabout giving the right of way to the vehicles already in circulation, and, once in the roundabout, must move in one direction with respect to the central island.

The advantages of a roundabout with respect to an intersection equipped with lights are:

- low cost,

- increased traffic capacity,

- possibility of changing the direction of travel, - elimination of waiting times.

But in many situations the number of vehicles and traffic density is so high that just a roundabout is not adequate to handle intersecting traffic flows. Given the above, a new type of road intersection was developed with at least two roundabouts substantially concentric at different levels, one at a lower level, external, another at an upper level, internal, for roads with high traffic flow, which improves the benefits of roundabouts of the known type.

The new intersection comprises in its main parts:

• Structures on two planes substantially parallel and overlapping;

• At least two substantially concentric 360° roundabouts placed on said two planes, where the roundabout lying on the upper level is internal while the roundabout lying on the lower level is external and runs along the projection of said internal roundabout;

• Four or more roads that lead to said lower external roundabout;

• Three or more roads that lead to said higher internal roundabout. While each of said four or more main roads lead to the lower roundabout, preferably only three of said roads have, each of them, at least one or more additional lanes that go up, running centrally with respect to the roadway lanes that join the lower external roundabout and arrive at said upper roundabout.

Said lower roundabout at a lower or ground level, runs externally with respect to the projection of said upper roundabout, located at the upper or first floor level, surrounding it, passing under the flyover constituted by the elevated lanes that arrive at said upper roundabout. In addition, the advantages characterizing the new road intersection with respect to other configurations are:

- Small size: by extending the height and not the width it can even be placed close to residential areas, and therefore handle traffic situations in urban environments;

- One structure design: this configuration has no hybrid junctions or secondary structures. It is a basic, simple but effective structure which also does not create discomfort from the visual-aesthetic point of view;

- Flexibility: it has a type of structure that would allow, at a later time, easy and economical structural changes or the addition of secondary structures in the event of changes in traffic flows;

- Low cost: the lack of hybrid junctions and secondary structures strongly affects the investment, scaling down costs considerably.

Figures 2 and 3 show the new road intersection.

In particular, the new road intersection consists of five main roads (A, B, C, D, E) with both directions of travel, each consisting of two or more lanes, where said roads converge towards two concentric central roundabouts (1 , 2) on overlying planes, one of which is an external lower roundabout (1) with a larger diameter, and one is an internal upper roundabout (2) with a smaller diameter.

In particular, said external lower roundabout (1) has an internal diameter greater or at least equal to the outside diameter of said internal upper roundabout (2), which is built on an embankment.

Each of said access roads (A, B, C, D, E) comprises at least one lane (Ae, Be, Ce, De, Ee) with a first entry (Al, B l , CI , Dl , El) on the right side with respect to the direction of travel, which leads to said external lower roundabout (1).

Said external lower roundabout (1) in turn has an exit (B12, C I 2, D12, El 2, A 12), on the right side with respect to the direction of travel for each of said main roads (B, C, D, E, A).

In addition, the new road intersection foresees that some of said main roads, for example three roads (A, B, C), each have at least one internal lane or preferably two internal lanes or more (Ai, Bi, Ci), beside said external one or more lanes (Ae, Be, Ce) that access said external lower roundabout (1), which go up to access said internal upper roundabout (2).

Said internal access lanes for said upper roundabout pass over said external lower roundabout thus creating a second entry (A2, B2, C2) for each incoming road (A, B, C) to said internal upper roundabout (2).

In turn, said internal upper roundabout (2) has an exit (B22, C22, A22) on the right side with respect to the direction of travel for each of said roads (B, C, A) that access said internal upper roundabout (2).

The flow of traffic can be adequately adjusted by appropriate and adequate road surface marking and road signs, whether fixed or variable.

Therefore with reference to the preceding description and the attached diagrams the following claims are made.

Claims

1. Roundabout for road intersections comprising three or more intersecting roads (A, B, C, D, E) with both directions of travel, characterized in that it comprises at least two roundabouts (1, 2), each of which is accessed by one or more lanes of said two or more roads (A, B, C, D), and where said roundabouts (1, 2) are substantially concentric and lying on planes at different heights, where a first roundabout, or lower roundabout (1) lies on a plane at a lower height, and a second roundabout, or upper roundabout (2) lies on a plane at a higher altitude.

2. Road intersection, according to claim 1 , characterized in that said lower roundabout (1) has an internal diameter greater than or equal to the outer diameter of said upper roundabout (2).

3. Road intersection, according to claims 1 or 2, characterized in that:

a. · each of said incoming roads (A, B, C, D, E) comprises one or more lanes (Ae, Be, Ce, De, Ee) on the right side with respect to the direction of travel, with entry (Al, Bl, CI , Dl , El) to said lower roundabout (1);

b. · two or more of said incoming roads (A, B, C) comprises one or more additional lanes (Ai, Bi, Ci), on the right side with respect to the direction of travel, with entries (A2, B2, C2) over passing said upper roundabout (2).

4. Road intersection, according to claim 3, characterized in that said access lanes (Ae, Be, Ce, De, Ee) for said first lower roundabout (1) run externally and substantially side by side to said access lanes (Ai, Bi, Ci) for said upper roundabout (2).

5. Road intersection, according to claims 3 and 4, characterized in that said access lanes (Ai, Bi, Ci) for said second internal upper roundabout (2) run centrally with respect to the related road (A, B, C) and then go up to join with said internal upper roundabout (2), over passing said external lower roundabout (1).

6. Road intersection, according to claims 1, 2, 3, 4, and 5, characterized in that said lower first roundabout (1) comprises, to the right with respect to the direction of travel, one exit (B12, CI 2, D12, El 2, A 12) for each of said access roads (B, C, D, E, A).

7. Road intersection, according to claims 1, 2, 3, 4, 5, and 6, characterized in that said second upper roundabout (2) comprises, on the right with respect to the direction of travel, an exit (B22, C22, A22) for each of said access roads (B, C, A).