SYSTEM FOR MAXIMISING AND CONTROLLING TIDAL FLOW OF TRAFFIC IN ROAD TUNNELS AND ON FREEWAYS

Field of the Invention ^■ ^ ^■

The present invention generally relates to motorways and freeways, and in one particular application, tunnels. Although the present invention will be most efficient benefits when applied to tunnels, similar efficiencies would also result from it being employed for ground-level motorways or above-ground viaducts. Accordingly, it is to be understood that the invention is not to be limited to tunnel arrangements but to carriageways using the same or similar configurations to those described and defined, even though, for convenience only, reference will only be made henceforth to "tunnel(s)".

Background to the Invention

The engineering and structural requirements and the resultant costs associated with the construction of a three-lane tunnel and any on/off ramps along its length are far in excess of what is required for that of a two-lane tunnel. This often renders it impractical and/or expensive, to the point of being unfeasible, for a road tunnel system to be more than four lanes - in a configuration of two lanes in either direction.

The present invention seeks to ameliorate one or more of the aboveraentioned disadvantages.

Summarv of the Invention

According to one aspect of the present invention there is provided a freeway road system which includes at least three carriageways, each carriageway including at least one lane for carrying vehicles thereon, wherein at least one carriageway is configured as a tidal flow carriageway which is adapted to carry vehicles in one direction at selected times and carry vehicles in an opposite direction at other selected times,

Preferably at least one of the carriageways is a tunnel. Optionally, the carriageways are tunnels. In one optional embodiment, at least two of the carriageways are unidirectional carriageways. .

Preferably there are three carriageways provided which are arranged side by side, the arrangement being such that two outer carriageways are disposed adjacent and laterally of a central carriageway, the central carriageway being the tidal flow carriageway and the outer carriageway being the unidirectional carriageway.

Preferably, the or each carriageway includes two lanes each so as to increase vehicle flow in the freeway road system.

In one optional embodiment exit and entry ramps are provided which facilitate exit and entry of a vehicle from each carriageway into another carriageway which extends in a different direction from that in which the tunnel system extends, the exit and entry ramps each including at least one lane and a vehicle control apparatus which includes a vehicle filter for filtering vehicles into adjacent lanes.

Preferably the vehicle filter includes at least one elongate barrier member which extends in use generally in a vehicle flow direction, the or each elongate barrier member being movable at one or more of its ends perpendicular to the vehicle flow direction so as to diagonally extend across a lane in which vehicles are flowing or approaching to direct the

vehicles to an adjacent lane.

Preferably the vehicle control apparatus includes two elongate barrier members, each of which is fixed at an upstream end and which are independently movable at downstream ends so as to direct vehicles into adjacent lanes.

Preferably the exit and entry ramps include first, second and third lanes which service one carriageway each, wherein a fixed lane dividing barrier is disposed between the second and third lanes, the fixed lane dividing barrier extending at least a short distance past an upstream end of the vehicle control apparatus and at least a short distance past a downstream end of the vehicle control apparatus to inhibit vehicles in the third lane from entering the vehicle control apparatus.

Preferably an exit ramp is provided which is associated with a uni-directional carriageway and is connected to an entry ramp associated with the at least one tidal flow carriageway.

Preferably a supplementary traffic control apparatus is provided which includes at least one supplementary elongate barrier disposed at a downstream end of the traffic control apparatus to direct vehicles to an adjacent lane. Optionally, the or each supplementary elongate barrier is disposed adjacent an entrance to one of the tunnels and is movable at an upstream end so as to inhibit vehicles from the adjacent carriageway travelling in a reverse direction from entering an exit ramp.

Preferably the elongate barriers and supplementary elongate barriers are movable between an open position wherein the elongate barrier is aligned with a lane border and a diverting position wherein the elongate barrier gradually extends across the lane in a diagonal position.

Optionally, the traffic control apparatus includes two elongate barrier members which may be arranged in use so as to extend parallel to one another or diverge from one another from a common mounting point, the latter diverging arrangement being so as to inhibit access to

a carriageway or lane. Preferably the two elongate barrier members extend parallel to one another and are spaced apart from one another so as to direct traffic from adjacent lanes.

Preferably the or each elongate barrier member is in the form of a plurality of barrier elements which are operatively connected to one another with a flexible element so as to facilitate pivoting between each barrier element.

Preferably the flexible element is a cable so as to improve the strength of the elongate barrier member to resist vehicle impacts. In optional embodiments each barrier element is a concrete plinth so as to form a median strip when assembled together with other barrier elements. In preferred embodiments at least the end barrier elements include wheels or other engaging devices such as for example cogs to facilitate lateral movement across the lane. Preferably motors are included in at least the end barrier elements so as to power the engaging devices so as to laterally move. In optional embodiments, wireless transmitters and receivers are incorporated in the barrier elements so as to remotely control the movement of the barrier elements.

Preferably the elongate barrier member is movable between a deployed position and a stowed position. Optionally, the elongate barrier member is retractable and includes a plurality of barrier elements of graduating sizes in a telescoping arrangement so as to slide within one another when moving between the deployed and stowed positions. Preferably a recess is provided in a kerb so as to receive the plurality of barrier elements and stow them therein.

Preferably there is provided an interchange between a first and a second freeway, the first and second freeways having a plurality of carriageways associated therewith, at least a first one of the carriageways being bi-directional for managing peak tidal traffic flows, the interchange including: at Jeast one exit ramp including at least one iane and connecting at least one freeway lane from the first freeway with at least one freeway lane from the second freeway, the exit ramp including the traffic control apparatus which is adapted to direct traffic to either the uni-directional carriageway on the second freeway or the bi-

directional carriageway on the second freeway.

Preferably the traffic control apparatus is operatively connected to and fed by two converging lanes, at least one of which is from the bi-directional carriageway.

Preferably a first elongate member is provided, a second elongate member is provided, the first and second elongate members having spaced-apart pivoting mounting points adjacent lane edges, and a third elongate member being adapted to be mounted adjacent the pivoting mounting point of the second elongate member, the third elongate member being laterally movable at both ends thereof.

Preferably a transition is provided between the tidal flow carriageways and a second multiple-lane carriageway freeway extending in the same direction as the tidal flow carriageways, the transition including traffic control apparatus which includes traffic diversion devices to manage the tidal flow to and from the tidal flow carriageways.

Preferably an exit ramp is provided, so as to exit a first carriageway on a first freeway road extending in a first direction to a second tidal flow carriageway on a second freeway road extending in a second direction, the exit ramp being connected to and merging with another exit ramp from a lane .of a carriageway from the first freeway at a merging position, the exit ramp including a traffic control device to filter traffic from one lane to an adjacent lane, the traffic control device disposed at a position adjacent or downstream of the merging position.

Preferably the traffic control apparatus includes a plurality of light emitting devices adapted to be lit in one or more series to represent a line which indicates a driving direction to vehicle drivers.

Preferably the traffic control apparatus is operatively connected to and fed by two converging lanes, at least one of which is from the bi-directional carriageway.

Advantageously, the preferred embodiments, which include the addition of a third carriageway or tunnel, when employed with the tidal flow controls that is described herein, allows for doubling the capacity for traffic in the direction of peak flow and a "reserve" carriageway to be available in the event of a blockage of either of the other two as a result of incident/emergency or repair/maintenance.

The equivalent utility of two four-lane tunnels can be achieved with greater flexibility of use and less geographical and space constraints, at less than the cost of building two three- lane tunnels, and far less than the cost of four two-lane tunnels.

According to another aspect of the present invention there is provided a traffic control apparatus including: a traffic barrier for inhibiting traffic flow into selected carriageways or lanes, the barrier including at least one elongate barrier member which extends in use generally perpendicular to a traffic flow direction, the or each elongate barrier member being movable between a deployed position where it blocks traffic flow into the selected carriageway or lane and a stowed position where it allows traffic to flow into the selected carriageway or lane.

Brief Description of the Drawings

In order to enable a clearer understanding of the invention, drawings illustrating example embodiments are attached, and in those drawings:

Figure 1 shows a plan view of a first motorway or freeway having three two-lane carriageways and a second motorway or freeway having three two-lane carriageways, each in accordance with a preferred embodiment of the present invention, wherein a T- interchange also in accordance with a preferred embodiment of the present invention is shown for movement between the first and second freeways;

Figure 2 is a plan view of a cross-interchange between a first motorway or freeway having three two-lane carriageways and a second motorway or freeway having three two-lane carriageways in accordance with a preferred embodiment of the present invention;

Figure 3 is a plan view of a T-jπterchange between a first motorway having three two-lane carriageways and a second motorway having one two-lane carriageway and one four-lane carriageway in accordance with a preferred embodiment of the present invention;

Figure 4 is a plan view of a cross-interchange between a first motorway having three two- lane carriageways and a second motorway having one three-lane carriageway and one two- lane carriageway in accordance with a preferred embodiment of the present invention;

Figure 5 is a plan view of a cross-interchange between a first motorway having three two- lane carriageways and a second motorway having two two-lane carriageways in accordance with a preferred embodiment of the present invention;

Figure 6 is a plan view of a traffic control device which moves from a stowed position to a deployed position by felescopically extending across a lane in accordance with a preferred embodiment of the present invention;

Figure 7 is a side elevation view of Figure 6;

Figure 8 is a plan view of a transition between a three-lane freeway and a three two-lane carriageway in accordance with a preferred embodiment of the present invention;

Figure 9 is a plan view of an intersection between a highway and a freeway having three two-lane carriageways in accordance with a preferred embodiment of the present invention;

Figure 10 is a plan view of an intersection between a highway and a freeway having three two-lane carriageways in accordance with a preferred embodiment of the present invention;

Figure 11 is a plan view of a transition between a three-lane freeway and a three two-lane carriageway in accordance with a preferred embodiment of the present invention;

Figure 12 is a plan view of Figure 8 in- use showing vehicle flows in a tidal situation wherein two carriageways allow vehicle flow in a forward direction and one carriageway allowing vehicle flow in a reverse direction;

Figure 13 is a plan view of Figure 9 in use showing vehicle flows in the tidal situation of Figure 12;

Figure 14 is a pian view of Figure 10 in use showing vehicle flows in the tidal situation of Figure 12;

Figure 15 is a plan view of Figure 1 1 in use showing vehicle flows in the tidal situation of Figure 12;

Figure 16 is a plan view of Figure 8 in use showing vehicle flows in a tidal situation

wherein an incident or a maintenance period that requires closure of carriageway 1 and allowing vehicle flow in the forward direction in Carriageway 2 and allowing vehicle flow in the rearward direction in Carriageway 3;

Figure 17 is a plan view of Figure 9 in use showing vehicle flows in the tidal situation of Figure 16;

Figure 18 is a plan view of Figure 10 in use showing vehicle flows in the tidal situation of Figure 16;

Figure 19 is a plan view of Figure 11 in use showing vehicle flows in the tidal situation of Figure 16;

Figure 20 is a plan view of Figure 8 in use showing vehicle flows in a tidal situation wherein in an incident or maintenance period, the closure of Carriageway 2 is required and vehicles are allowed to flow in a forward direction in Carriageway 1 and vehicles are allowed to flow in the rearward direction in Carriageway 3;

Figure 21 is a plan view of Figure 9 in use showing vehicle flows in the tidal situation of Figure 20;

Figure 22 is a plan view of Figure 10 in use showing vehicle flows in the tidal situation of Figure 20;

Figure 23 is a plan view of Figure 1 1 in use showing vehicle flows in the tidal situation of Figure 20; and

Figure 24 is a front elevation view of the traffic control device of Figures 6 and 7.

Description of Preferred Embodiments

Referring to Figures 1 - 5 there is shown a freeway system generally indicated at 10 for carrying vehicles (not shown), the freeway system including a first freeway 12 including a plurality of carriageways 1, 2 and 3, and a second freeway 14 including a plurality of carriageways (4, 5, 6 in Figs 1 and 2). Carriageways 1 - 6 are shown in dashed lines 37 to indicate that they are in the form of underground tunnels. The tunnels interface with the ground at tunnel exits and entrances 19.

Figure 1 shows two groups of three carriageways 1, 2, 3 and 4, 5, 6 each having two lanes 21, 22 _> 23 _j 24, 25, 26, wherein one of the groups of carriageways is configured as a tidal carriageway, that being a central carriageway 2. In use, in normal situations, vehicles (not shown) may travel on the freeway system 10, in directions generally indicated by arrows 18, That is, vehicles in carriageway 2 will all travel in the same direction at the same time, but in one selected direction at a selected time and in the other direction at other selected times, depending on the requirements of the time and situation.

A traffic control apparatus 30 is provided which includes elongate barrier members 32, 34 and 36, which extend generally along the direction of traffic flow. Each barrier member is movable at one or more of its ends 33, 35, 37, 39, 41, 43 perpendicular to the traffic flow so that the barrier member 32, 34, or 36 can diagonally extend across a lane, 21 , 22, 23, 24, 25 or 26 so as to divert or direct vehicles to an adjacent lane.

Detail view "A" in Figure 1 illustrates the configuration of a first type of traffic control apparatus 30 wherein the elongate barrier members 32, 34 or 36 are in the form of movable or floating median strips 45, 47, 49- The traffic control apparatus 30 in Detail A includes two movable median strips 45, and 47 shown in Figures 1, 3, 4 and 5, and in use controls tidal, flow from a single lane entry ramp 42 _} onto a triple carriageway freeway 12.

Detail view "B" in Figure 1 shows a configuration of a traffic control apparatus 30 which includes a supplementary elongate barrier 48 which in use restricts access to an exit ramp 44 from carriageway 2, and which in use controls tidal flow from the double lane entry ramp 44 onto a triple carriageway freeway 14.

It is noted that in Figures 1 to 5 each traffic control apparatus 30 is illustrated in an "open" position - that is unrestricting to traffic flow, the elongate barriers 32, 34, 36 being aligned with a lane dividing line 61 - with arrows and dotted lines indicating the median's "closed" position. However, the detail views show the median sets with all floating medians in a "closed" or restricting position.

Each traffic control apparatus 30 is denoted in Figures I to 5 by a number from "60" to "63". Within each traffic control apparatus 30, each floating median strip 45, 47, 49 is denoted by a letter, "a", "b" or "c". Each letter denotes a floating median strip 45, 47, 49 with the same function in all diagrams as follows: Median strips marked "a" in use allow or restrict access to the leftmost of the three carriageways (1 and/or 4 in one direction, 3 and/or 6 in the reverse direction), from entry ramps, (Figures 1 to 5). Median strips marked "b" in use allow or restrict access to the middle of the three carriageways (2 and/or 5), from entry ramps, (Figures 1 to 5). Median strips marked "c" in use restrict access to the entry ramp from the middle of the three carriageways (2 and 5), (Figures 1 and 2),

Traffic control apparatus 63 and 62 includes floating median strips 45, 47 marked "a" and "b". In use, tidal flow control is afforded according to the following conditions: if "a" and "b" are open, then entry ramp access is permitted to a left-hand carriageway only, ("b" being "open" allows traffic flow in the opposite direction along the adjacent lane); if "a" is open and "b" is closed, then entry ramp access is permitted to both the left and middle carriageways, ("b" being "closed" restricts traffic flow in the opposite direction along the adjacent lane).

If "a" and "b" are closed, then entry ramp access is permitted to the middle carriageway only.

It is noted that the configuration of "a" closed and "b" open would result in access to both carriageways being blocked which would not be required except in unusual circumstances.

Traffic control apparatus 60 and 61 includes supplementary elongate barriers marked "c". Median strips "b" and "c" work in unison in that both must be either open or closed at the same time to control tidal flow between the entry/exit ramp 44 and middle carriageway. Tidal flow control is afforded according to the following conditions: if "a" is open and "b"/"c" are closed, then entry ramp access is permitted to the left carriageway only; if "a" and "b"/"c" are open, then entry ramp access is permitted to the left and middle carriageways; if "a" is closed and ^t(1 b'7"c" are open, then entry ramp access is permitted to the middle carriageway only. Note, the configuration of "a" and "b'V'c" closed would result in access to both carriageways being blocked which would not be required except in unusual circumstances.

Traffic control apparatus 62 includes a fixed median strip which extends a short distance past a downstream end of the elongate barrier elements so that vehicles in an adjacent lane 98 are inhibited from entering the traffic control apparatus 62.

The floating median strips 45, 47, 49 are a plurality of barrier elements connected to one another by a cable 97 so that they may resist vehicle impacts and so that only one element need be moved, and the others will follow. Motors may power an end barrier element, and wireless control systems may control their lateral movement.

Referring to Figure 2, there is shown a cross-interchange between three two-lane carriageways 1, 2, 3 and 4, 5, 6. An exit ramp 44 is connected to a lane of carriageways 4 and 5, and the ramp 44 turns towards the carriageways I and 2. Another exit tamp 144 is connected to a lane of carriageways 5 and 6, and the exit ramp 144 merges with exit ramp 44 at a merging point 71. Downstream of the merging point 71 , a traffic control apparatus 60 diverts traffic to either the carriageway I or carriageway 2.

There are 5 normal situations for preferred embodiments of the present invention:

1. 2 carriageways carrying traffic forward, 1 in reverse;

2. 1 forward carriageway, 2 reverse;

3. Closure of carriageway 1 ; 4. Closure of carriageway 2;

5. Closure of carriageway 3.

Figures 1 — 5 and Figures 8 -23 show various arrangements of various traffic control devices 30 which are disposed at entrances to the carriageways 12 and 14 in order to safely bring about the 5 normal situations- The traffic control ^" devices 30 may be lights, signs, movable barriers.

Figure 9 shows an interchange 50 between a freeway 10 and a highway 50 which includes exit and entry ramps 52 in both directions for each of three carriageways 1, 2, 3. It is believed that this would be a more expensive interchanges to construct than the one shown in Figure 10. However, it is believed that the interchange 50 in Figure 9 should allow less possibility for driver confusion, because in use, vehicles will always be directed to travel in a single, unchanging direction along any given exit or entry ramp 52. In a situation where in use, an exit/entry ramp is accessible to a Vehicle travelling in an opposite direction to the single direction of the exit / entry ramp, the ramp is simply closed.

Some exit/entry ramps 52 may function as supplementary ramps 53 for Caπϊag jei way 2, in the event of a temporary closure of an exit/entry ramp 54.

Traffic control apparatus 30 may include overhead electric lane indicators and/or traffic lights, however, there exists a real danger for driver error which could result in vehicles traveling in the wrong direction onto a carriageway. Therefore, median strips are preferred. This, of course does not mean that such things as electric lane indicators could not be used as an aid to the floating median strips.

In Figures 8 to 11 , an arrow, marked with the label, A, B or C ₅ of each floating median strip, indicates its direction of movement.

Traffic control devices 30 are also provided in Figures 8 to 11 ₃ in the form of floating median strips, labeled "B" & "C". The advantage of these twin median strips is that they can be used together as a single median strip, or pivoted apart to work separately, in order to perform their various functions of routing traffic m and out of the tunnel entrances.

Review of Figures 8 to 11 will show that the ends 85 and 86 of median Strips B and C can move laterally across the flow of traffic, which effectively means the median strips B and C pivot about end point 81. In addition, the end 84 of Median Strip C can translate laterally from the end of the median strip 87 separating the two ground-level carriageways 7 and 8 to the outer kerb 88 of the outward-bound, ground-leve! carriageway.

For obvious safety reasons, the upstream, (moving) end 85, 86 of the median strips B and C should not move across the face of oncoming traffic during changes of tidal flow. Therefore, an extra, single median strip (marked "A" on Figures 8 to 11) is provided. In this and later examples, the function of this median strip is, in Figure 8 to restrict access to Carriageway 1 and, in Figure 11 to restrict access to Carriageway 3, when required.

The end 79 of Median Strip A can translate between the outer kerb of the inward-bound, ground-level carriageway 89 and the end 91 of the divider 92 between Carriageways 1 & 2 in Figure 8 and Carriageways 2 & 3 in Figure 11.

Figures 12 - 23 only show the floating median strips that are actually used to control traffic flow in each example. If a median strip is not shown, it can be presumed that it has no relevance for that situation and has therefore been left in an open and non-restricting or kerb-side position.

Traffic on the sections of roadway diverging from or converging to double and triple carriageways 7, 8 or 9 can be further controlled and exactly channeled when the floating

median strips are used in conjunction with correctly designed, variable lane markers on the road surface. The positions of these lane markers will obviously need to change as the direction of traffic flow between carriageways changes. This will require several lines of iane markers along the sections of road that connect the double and triple carriageways. The various positions of these lines of lane markers would be too complicated for motorists to understand if ordinary lane separators were to be used, as all would be visible at the same time.

One solution to this problem lies in the use of multiple lines of light emitting devices 80, known as illuminated raised pavement markers 82. When illuminated, these markers SO are clearly visible in daylight but they are invisible when switched off and not in use. A line of these markers 80 will only be illuminated when it indicates the separation of lanes that are in use at any time. During periods of tidal flow change, it may also be desirable that lines of markers which define the paths of lanes that are changing should flash on-and- off while the floating median strips pivot slowly to their new positions, to aid driver awareness of the changing situation and correctly channel traffic flow.

Wherever a lane is terminated as indicated by the termination symbol 99 in the Figures, signage will be used to safely, and with due notice, warn traffic of the need to merge.

Review of Figure 9 will show that the transition depicted requires floating median strips at two of its junctions of entry/exit ramps with Carriageway 2. The function and direction of movement of these floating median strips, if used, are very simple and are illustrated by unlabeled arrows on the diagram.

Floating median strips should not be required at any of the other junctions of carriageways and on/off ramps because, as Figures 12 -23 will show, the ramps will either be in use, their orientation will be against the flow of traffic, (with the flowing traffic obviously unable to reverse into them), or because the carriageway and its exit/entry ramps are closed to traffic, with access to them already blocked elsewhere.

As mentioned previously, one of the main benefits of the interchange shown in Figures 9 and 10, is its simplicity. Among other things, there is no need for any floating median strips, because if a carriageway is open, all of its on/off ramps will be open for traffic.

There is, however, a greater need for directional control at the intersections of the on/off ramps and crossroads, due to the possibility for driver error at these points. Conventional technology, such as traffic lights including arrow indicators, and other variable electric signage will be of use, particularly in alerting drivers to their options on approach to the intersection.

A very safe option for the closure of a ramp at its intersection with a crossroad will be the use of an extendable, (as opposed to floating), median strip. As with all the other movable median strips, it will be electronically controlled. It could be, for example, constructed of a series of segments that, when not in use, could telescope into a single segment that would, in turn, roll into a compartment under the footpath of the crossroad when the ramp is open to traffic and the median strip is not in use.

When required for use, in conjunction with traffic lights and arrows, appropriate signage and possibly overhead, electric lane indicators, it will open out, possibly using a rail to keep the correct path, until it extends from the kerb to the other side of the lane, blocking access to it completely.

Figures 6 and 7 illustrate an example of such an extendable median. It illustrates a working example of the extendable, segmented median strips featured in Figure 10, showing plan, front and side perspectives. The median strip is depicted in its extended position, restricting access to its adjacent entry ramp.

Preferred embodiments of the present invention employ systems (or "sets") of "floating medians", or similar tidal flow controls, on the entry ramps to the triple carriageways.

A "median set" is defined here as a plurality of pivot able (or "floating") median strips associated together by their proximity and their single and simultaneous function of directing traffic flow at a particular location.

These sets of floating medians could be replaced by manually controlled lane separators such as the so-called "candy sticks" or "candy bars", ϊt is envisaged, however, that some form of physical tidal separation, as opposed to signage or lights, would be required, because of its virtually "foolproof method of physically forcing traffic along the correct ramps/lanes. Whatever method is ultimately employed, the intent of this document is rather to address the configuration and direction of any and all such traffic controls.

Other features and advantages of preferred embodiments of the present invention are noted below:

It is envisaged that as vehicles egress from the carriageways 1 —6 there would need to be a number of lanes available that is equal to or greater than the total number of lanes of two tunnel carriageways, (hence the four-lane carriageways depicted in this model), even if one or more lanes are terminated further along the freeway at, for example, an exit. Otherwise, there is potential for traffic hold ups to occur at any time when two -tunnel carriageways converge to one after exit. The resultant delays would extend back into the tunnels and thereby defeat many of the benefits of the present invention.

Using preferred embodiments of the present invention will greatly reduce the complexity of design and the land area required for the construction of such systems, and the associated costs for engineers and builders, as well as later administration costs for operators.

Other advantages of preferred features of the present invention include: the minimisation of the number of exit/entry ramps needed to achieve all permutations of interchange between the freeways' carriageways, even allowing for changes of tidal flow or closures on the triple carriageway system($); straightforward navigation for drivers and tidal flow management for freeway operators.

Due to the simplicity of preferred embodiments of the present invention in managing tidal flow using the median sets, as well as other preferred features described herein it is not necessary to include separate diagrams for each example of directional traffic flow.

It is therefore assumed and obvious that if a flow control is not used here, then traffic has already been restricted/controlled elsewhere in the system, if that need exists. Further, it is implied that the timing of all controls for the opening, closure and/or reversal of traffic flow on carriageways and/or ramps would be determined by the local traffic authority, who would allow for these to be achieved safely and efficiently - and that this is common practice already. Extra traffic flow restrictions could be catered for in certain circumstances if required,

In Figure 3, only three single-ievel overpasses and two movable traffic control apparatus are required to achieve several tidal flow methods of use.

Furthermore, the "T'-intersections depicted in Figures 3 and Figure 1 could be adjusted to other angles of interchange, including "Y" intersections, with minimal or no alteration to the configurations shown.

The arrangement shown in Figure 4 includes only one single-level overpass and two median sets to achieve several tidal flow arrangements, assuming that the three two-lane carriageway is in the form of underground tunnels.

The arrangement shown in Figure 5 includes only six single-level overpasses and four median sets to achieve several permutations of tidal flow, assuming that the three two-lane

carriageway is in the form of underground tunnels.

The arrangement shown in Figure 1 includes only one single-level overpass and four median sets to achieve several permutations of tidal flow _} assuming the freeway 10 is underground.

The arrangement shown in Figure 2 includes only four single-level overpasses and four median sets to achieve several permutations of tidal flow, assuming both freeways are underground. The number of overpasses increases to six single-level and two double-level overpasses if one of the freeways is at ground-level.

A singular additional feature of the arrangement shown in Figure 2 is the employment of twin, unidirectional on- and off-ramps between each of the triple carriageway roads. This, along with the design of the four illustrated median sets, allows for a very simple and economical solution to a complex challenge in design, construction and tidal flow control.

Although it is envisaged that the situations depicted in Figures 1 and 2 would be rare, they are nevertheless included in this document for comprehensiveness, and to illustrate that the present invention can, in conjunction with a number of preferred features, be applied in all possible situations of interchange between triple carriageway systems and dual or triple carriageway systems.

The triple carriageways in Figures I and 2 are all depicted as tunnels. It is possible, even likely - though not necessary - that one of the freeways would be at or above ground level, particularly within the cross-interchange depicted in Figure 2. In any case, it would normally be more economically feasible for the exit/entry ramps linking the freeways to be at or above ground level, depending on the surrounding topography and/or land use.

For the cross intersections depicted in Figures 2 and 5, the overall shape, (though not the exact configuration), of the intersection shown in Figure 5 could be swapped with the "diamond" shape of the interchange shown in Figure 2 and vice versa - once again

depending on the amount and orientation of land available, the cost of same and the surrounding topography.

The Figures are not to scale, especially the lengths of on/off ramps and merging lanes, the radϋ of curves, and implied gradients. Further, any or all over/under-passes, ramps and carriageways depicted as tunnels, or as at- or ab'ove-ground level could swap according to the land available, surrounding topography and economics and other conditions of design.

Throughout this document it is assumed that vehicles travel on the left-hand side of the road. Opposite configurations of the freeway system for travel along the right-hand side of the road are obvious.

Preferred embodiments of the present invention assume that the timing of opening, closure and/or directional change of carriageways, lanes, median strips and on/off ramps can be determined by the local traffic authority to allow for the safe and efficient tidal change of traffic flow. This is presumed to be common practice already and not necessary to be described or explained further in this document.

In the rare event of two of the three tunnels being out of service for any reason, there is scope for the one remaining tunnel to accommodate traffic travelling in one direction, (presumably that of heaviest flow at the time), with traffic travelling in the opposite direction re-routed along surrounding streets, as is normal with current dual carriageway systems.

Contributing to the simplicity of this system is that the median sets need only be employed to control tidal flow on the entry ramps to the triple carriageway roads, because traffic flow on the exit ramps will have already been restricted elsewhere on the freeway. Accordingly, only the controls that are necessary to achieve the relevant tidal flow and interchange permutations are shown.

There is, however, also scope for permitting (albeit minimal) traffic flow in both directions in one tunnel, though this would be severely restricted and would need to be profoundly speed/safety controlled because of the obvious potential hazards resulting from no physical separation of bi-directional traffic in one tunnel.

The present invention could be extended from three two-lane carriageways, to four or more two-lane carriageways, which would be more efficient and economical manner than two carriageways of four or more lanes. Furthermore, preferred embodiments of the present invention will be effective in configurations of, for example, three by three-lane carriageways and other like configurations. The present invention is by no means limited to a three-carriageway system of two-lanes each as shown in the preferred embodiments But is intended to embrace all like permutations.

Advantageously, preferred embodiments of the invention provide a correct, safe and expeditious movement of vehicles between double and triple carriageways and at interchanges between the three carriageways and other roads, especially during changes of tidal flow. Preferred embodiments of vehicle control apparatus provided to facilitate the vehicle movement include electronic signage and lane marking, as well as "floating" median strips.

Advantageously, preferred embodiments of the present invention will result in great savings in land acquisition and the costs of design and construction and later traffic flow admiπistration.

Finally it is to be understood that the various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.