DE STAVOLA, Gianmaria (Galleria Spagna 10, Padova, I-35127, IT)
| CLAIMS 1. A road interchange, comprising two main traffic streams (X, Y) that intersect (S) to generate four merging roads (A, B, C, D) with two or more lanes, comprising at least one overpass between said two traffic streams (X, Y) that retain a substantially linear configuration, characterised in that, for each of said merging roads (A, B, C, D), it comprises: at least one first junction (A1, B1 , C1, D1) with one or more lanes on the right, in relation to the sense of the traffic flow, with a rightward deviation of approximately 90° that makes it merge to the right, in relation to the sense of the traffic flow, of the corresponding road on the right (B, C, D, A); at least one second junction (A2, B2, C2, D2) with one or more lanes on the right, in relation to the sense of the traffic flow, with an initial rightward deviation and a subsequent leftward deviation, so that it merges to the right, in relation to the sense of the traffic flow, of the corresponding road on the left (D, A, B, C), wherein said second junction (A2, B2, C2, D2) of each merging road (A, B, C, D) passes over at least the corresponding merging road on the right (B, C, D, A) and the opposite merging road (C, D, A, B), so that it merges to the right, in relation to the sense of the traffic flow, of the corresponding road on the left (D, A, B, C). 2. A road interchange according to claim 1, characterised in that said second junction (A2, B2, C2, D2) of each merging road (A, B, C, D) passes over or under at least one of the second junctions (B2, C2, D2, A2) of the other three merging roads (B, C, D, A). 3. A road interchange according to claim 2, characterised in that said second junction (B2, C2, D2) of one or more of said merging roads (B, C, D) passes over the second junction (D2, A2, B2) of the road opposite (D, A, B). 4. A road interchange according to claims 1, 2, 3, characterised in that the combination of said second junctions (A2, B2, C2, D2) on the four roads (A, B, C, D) forms a circular or oval, or egg-like shape. 5. A road interchange according to claim 4, characterised in that the central reserve coming between said second junctions (A2, B2, C2, D2) comprises an area for stopping and parking, service and refuelling stations, buildings for catering services and other amenities. 6. A road interchange according to claim 5, characterised in that one or more of such areas for stopping and parking, service and refuelling stations, buildings for catering services and other amenities are located in the vicinity of the overpass between said two main traffic streams (X, Y). 7. A road interchange according to claim 5, characterised in that said areas for stopping and parlcing, service and refuelling stations, buildings for catering services and other amenities are located so as to enable communication between them and between said roads (A, B, C, D), with at- grade or grade-separated pedestrian paths and vehicle roads. |
DESCRIPTION
This patent relates to road interchanges and particularly concerns a road interchange for roads with a high traffic flow density of the type with a central grade separation.
There are known grade-separated road interchanges that adopt configurations which take into account:
the available space;
the traffic flow density on the main axes and on the access slip roads; · the required service level;
the feasibility of achieving a grade separation on more than two levels.
The object of the present patent is interchanges between roads that are at least dual carriageways and cannot be interrupted with roundabouts, and that are compact, due to the need to contain the space they occupy to no more than two levels in order to avoid generating major differences in the elevation, lengths and costs of construction.
The layout of the known types of interchange discussed below are schematically il lustrated in the drawings.
Figure 1 shows a cloverleaf layout.
The examples shown are compared as a function of the importance to attribute to the various parameters, and in particular to the landtake, the capacity and the safety of the interchange, and the related cost.
The cloverleaf layout comprises two main traffic streams (X, Y), each with at least a dual carriageway and intersecting one another (S) to generate four merging roads (A, B, C, D) with a grade separation between said two traffic streams (X, Y) that maintain a substantially linear configuration.
In the cloverleaf layout, for each merging road (A, B, C, D) there is a first junction (A1, B1, C1, D1) on the right, in relation to the sense of the traffic flow, with a rightward deviation of approximately 90° that merges on the right of the corresponding road to the right (B, C, D, A), in relation to the sense of the traffic flow,
Moreover, for each merging road (A, B, C, D), beyond the intersection (S), there is a second junction (A2, B2, C2 D2) on the right, in relation to the sense of the traffic flow, with a 270° rightward deviation that merges on the right of the road to the right (B, C, D, A), in relation to the sense of the traffic flow.
The cloverleaf layout involves a greater landtake than other interchanges: for the same planimetric radii of curvature, it occupies all the quadrants in which the main roads divide the area.
The interchange layouts without weaving areas are bulky and costly crossroads on three levels, or hybrid combinations of cloverleaf layouts and innovative, more efficient layouts, as shown below.
The cloverleaf configuration is only suitable for weaving traffic streams with under 1.000 vehicles per hour and, in any case, it generates discontinuities in the travelling speed along the main carriageways with consequent risks to the traffic.
The double loop configuration also appears suitable only for weaving traffic streams with under 1000 vehicles per hour, but it is safer than the cloverleaf solution, because weaving takes place in a lower speed sector. The layouts without weaving areas have no traffic capacity limits because they are characterised by the fact that the number of lanes on the slip roads can be calibrated to suit the traffic flow densities.
The cloverleaf is the least costly to construct because the greater Iandtake is compensated by the need for only one construction (the main overpass). The other interchange layouts demand several structures, which makes them more expensive, despite their reduced Iandtake.
The pros of a cloverleaf interchange are the need for only one construction, while the cons he in that the capacity to weave between traffic streams on the main roads is limited by the existence of weaving areas where some vehicles leaving the carriageway must cross over the merging lanes. This weakness depends on the length of the weaving area and on the number of weaving lanes; the weaving length is normally restricted to 200-300 m, i.e. to values that make it necessary to restrict to the merging and diverging traffic streams to one lane.
A single merging lane disturbed by the weaving of diverging vehicles, which have right of way in the weaving process, restricts the weaving capacity to approximately 1000 vehicles per hour on each slip road.
This weaving takes place at the speed typical of the right-hand lane of the main carriageway and can be a cause of hazardous abrupt slowdowns.
The double loop solution is an evolution of the cloverleaf, with a view to making the weaving take place in sectors characterised by lower speeds.
The pros are that the weaving between the flows is confined to low-speed stretches and the Iandtake for the junction is reduced.
The cons are the need to build three structures and the fact that the weaving capacity for the traffic streams on the main roads is limited by the existence of weaving areas; their length is normally restricted to 200-300 m, i.e. to values that make it necessary to restrict the lanes merging into the weaving area to one; the weaving capacity is thus approximately 1000 vehicles per hour for each slip road.
The "no weaving" solutions without interchanges differ conceptually from those described above, since each slip road is independent of the others. In this case, slip roads can be made with more than one lane, depending on the traffic flow densities, and the lane capacity is not restricted by weaving areas, and is not disturbed.
The advantages of this solution lie in that there is no weaving between the traffic streams, but only merging manoeuvres, the number of lanes is not limited, the landtake is less than for a cloverleaf, and many manoeuvres are either direct or semi-direct
The disadvantages lie in that three constructions are needed and the length of the slip roads and the supporting works is greater than for the other layouts.
In the light of the above-described situation, a novel road interchange layout has been studied, called the egg-shaped road interchange, that draws from up and improves on the advantages of the no weaving layouts.
It is characterised in that:
. each slip road is independent of the others;
the slip roads can be made with more than one lane, depending on the traffic flow densities;
. the capacity of the lanes is not limited by the existence of weaving areas;
• for the same radii of curvature, the overall dimensions of the interchange are smaller than for other layouts.
In addition, the advantages and particular features that distinguish it from other layouts are as follows.
The slip roads are of the direct or semi-direct type, so any "loops", i.e. 270° deviations that demand reduced radii, discomfort and slowdowns, are avoided.
The plariimetric radii of curvature, and consequently the performance in terms of comfort, are in fact greater than with other types of interchange. The interchange's central reserve, over a length of several hundred metres and for both the roads that intersect one another, is free of merging and diverging lanes, so the space delimited by the slip roads can be used for commercial enterprises and services accessible to users of both the roads. The use of the central reserve has advantages in that the users served by the activities and services is the sum of the users of the two roads, and consequently twice the numbers achievable by a similar installation normally located on one side of the road
The installation area comes within the area that would in any case be occupied by the interchange, and consequently does not demand any further landtake.
The interchange between local traffic and through traffic is concentrated in a place that is readily equipped with services and park-and-ride car parks. The attached figure 2 shows the novel road interchange, comprising two main traffic streams (X, Y) that intersect (S) to generate for merging roads (A, B, C, D) with two or more lanes, comprising at least one overpass between said two traffic streams (X, Y), which retain a substantially linear configuration.
For each merging road (A, B, C, D), the novel road interchange comprises a first junction (A1, B1, C1, D1), with one or more lanes, on the right in relation to the sense of the traffic flow, with a rightward deviation of approximately 90° so that it merges on the right of the corresponding road (B, C, D, A), in relation to the sense of the traffic flow.
For each merging road (A, B, C, D), the novel road interchange also comprises a second junction (A2, B2, C2, D2) with one or more lanes, on the right in relation to the diverging direction, with an initial rightward deviation (A21, B21, C21, D21) and a subsequent leftward deviation (A22, B22, C22, D22) so that it merges on the right, in relation to the sense of the traffic flow, of the corresponding road on the left (D, A, B, C).
Said second junction (A2, B2, C2, D2) on each of said four roads (A, B, C, D) passes over (Ap1, Ap2, Bp1, Bp2, Cp1, Cp2, Dp1, Dp2) at least the corresponding merging road to the right (B, C, D, A) and the opposite merging road (C, D, A, B), so that it merges on the right (Dd, Ad, Bd, Cd), in relation to the sense of the traffic flow, of the corresponding road on the left (D, A, B, C).
In the preferred embodiment, moreover, said second junction (A2, B2, C2, D2) on each of said four roads (A, B, C, D) passes over or under at least one of said second junctions (B2, C2, D2, A2) of the other three roads (B, C, D, A).
In detail, as shown in figure 2, said second junction (B2, C2, D2) on the roads identified as B, C, D also passes over (Bp3, Cp3, Dp3, Dp4) at least the second junction (D2, A2, B2) of the road opposite (D, A, B).
Said second junctions (A2, B2, C2, D2) on the four roads (A, B, C, D) combine to form a circular or oval, or egg-like shape.
In the central reserve coming between said second junctions (A2, B2, C2,
D2) there may be one or more areas for stopping and parking, service and refuelling stations, buildings for catering services and other amenities.
Moreover, one or more of said areas for stopping and parking, service and refuelling stations, buildings for catering services and other amenities can be located in the vicinity of the overpass between said two main traffic streams
(X, Y).
In addition, said areas for stopping and parking, service and refuelling stations, buildings for catering services and other amenities can be located so as to enable communication between them and between said roads (A, B, C, D) with at-grade and/or separated grade pedestrian paths and vehicle roads.
Figure 3 schematically shows how the novel interchange has a landtake substantially smaller than the known cloverleaf interchange.
Thus, with reference to the above description and to the attached drawings, the following claims are advanced.
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