Transportation systems

Abstract

A transportation system including a network of tracks for remotely-controllable vehicles to run over, having intersections each enabling vehicles to be driven from one track to another track, and each comprising a junction track associated with vehicle detector means, signalling means and a computer for controlling vehicles on or approaching the junction track. A length of the junction track may be designated as queueing space sufficient to accommodate a predetermined maximum number of vehicles Q, and the computer may include means for maintaining a record of the number of vehicles q currently allocated to the queueing space, and a list of turn priorities for given destinations, and means for sending turning command signals to any vehicle whose destination gives it a turn priority greater than q, provided that q is less than Q.

Description

BACKGROUND OF THE INVENTION

The present invention relates to transportation systems, and particularly to transportation systems in which comparatively small, remotely-controllable vehicles are driven over a network of tracks. Such systems have been proposed as an answer to problems of urban and suburban transportation, offering the advantages of greater convenience than most conventional omnibus or train services, greater economy than conventional taxicabs, and a prospect of allowing a greater traffic capacity in a given space than conventional road transport.

To achieve a high traffic flow rate, it is desirable that vehicles should be able to move in a regular stream (in which the individual vehicles move with substantially the same speed as each other, matching their speed to the speed of the stream which is generally maintained at chosen speed) over at least a major part of each journey. To facilitate this, various systems have been suggested in which vehicle control signals have been linked to and synchronized with periodic master timing signals. Difficulties and complications arise, however, because many essential operations in the system are inherently asynchronous. For instance, loading and unloading operations will require vehicles to be taken out of, and fitted back into the traffic stream. It is difficult to make arrangements for the merging of traffic streams consistent with any plan for the completely synchronous operation of all traffic streams in a very busy system. The problems and difficulties involved are not too serious if the utilization factor (that is the number of vehicles actually travelling on the track divided by the total number of track spaces available) is low. However in urban situations, where there is a great demand for transport facilities and space is at a premium, it is desirable to attempt to satisfy the maximum demand with tracks occupying the minimum amount of space; it will therefore be advantageous to operate the system as near as possible to its theoretical maximum capacity, increasing the number of vehicles in use and reducing the amount of free track space not occupied by any vehicle. This greatly increases the difficulties of the merging and control processes, especially if it is desired to use the highest possible utilization factor while maintaining a good traffic flow rate and retaining a good degree of versatility in the choice of routes and stopping places to suit individual requirements.

One suggested solution, which can be called the chess-playing or complete-schedule method, is to have a computer arranged to keep track of the positions of all vehicles in the system and to tabulate their predicted positions at a series of times sufficient to complete all their journeys; before any vehicle is allowed to join or rejoin any traffic stream, predictions of its proposed journey are compared with the tabulation, and it is not allowed to start until all these predictions fit into unoccupied spaces in the tabulation. This arrangement has the disadvantage that the amount of computing required increases approximately according to a power of the size of the system, and it is very inflexible.

Congestion at a popular destination could for instance in this arrangement prevent persons setting out on their way to it, instead of allowing them the option of getting the nearest uncrowded station, or approaching the destination by an alternative route. An even more important disadvantage of any system attempting to achieve completely synchronous, completely scheduled operation of all traffic streams with a high utilization factor is the disruption of the scheme which is liable to be caused by a fault in any vehicle or part of the control system. While vehicles and control systems can be made highly reliable, it will be uneconomic if not impossible to ensure absolute reliability, and in any system of practically useful size some possibility of breakdowns should therefore be accepted and allowed for. In a complex system with many junctions and completely scheduled operation, any breakdown is liable to have extensive repercussions; places which should become vacant do not become vacant, and places are reserved for vehicles unable to come into them because of obstruction. The whole schedule has to be re-planned and places reallocated taking into account the effects of the fault. The amount of computation required for such reallocation rises as a power of the size of the system, and with a high utilization factor in a system of only moderate complexity it is likely to require the whole system to be brought to a standstill while a new schedule is worked out. The probability of such a standstill, with the accompanying waste and annoyance which it would cause, in effect places an economic or tolerance limit on the complexity and utilization factor of any system of completely synchronized traffic streams.

SUMMARY OF THE INVENTION

These disadvantages can be avoided by a control system which is convenient for both synchronous and asynchronous operation, does not attempt complete scheduling or prediction of the whole route of every journey, and accepts a possible need for asynchronous operations or queueing at any junction. This kind of system, hereinafter called a Cabtrack system, allows more freedom in route selection and modification; it can be arranged to direct vehicles around any obstruction or congested area.

It is an object of the present invention to provide a transportation system wherein remotely controllable vehicles can be controlled to form separately synchronized traffic streams on different tracks, and to make controlled transfers from one stream to another at intersections, by control apparatus which can operate as a plurality of self-sufficient, comparatively simple decoupled parts, regardless of the complexity of the system as a whole.

According to the present invention, there is provided a transportation system comprising a plurality of tracks and a plurality of remotely controllable vehicles constructed to run over the said tracks, wherein the said tracks comprise at least a first main track, a second main track and a junction track by which vehicles may be driven from the first main track to the second main track, and the system also comprises first signalling means for sending control signals to vehicles on the first main track such that all vehicles on a continuous extended length thereof receive the same control signals to cause the said vehicles to proceed in a first regular traffic stream along the said first main track, means for sending signals to selected ones of the said vehicles to divert them on to the junction track, second signalling means for sending control signals to vehicles on the second main track such that all vehicles on a continuous extended length thereof receive the same control signals to cause the said vehicles to proceed in a second regular traffic stream along the said second main track, third signalling means for sending control signals to vehicles on the junction track to control their progress on the junction track and to make them responsive to signals derived from the second signalling means at selected times, further means for sending control signals derived from the second signalling means to vehicles on a part of the junction track to cause the said vehicles to match their speed to the speed of the said second regular traffic stream, a plurality of vehicle detector means for detecting the passage of vehicles on the first main track, the second main track, and the junction track and receiving data signals from said vehicles, and computer means connected to the vehicle detector means and to the first, second and third signalling means for controlling the transfer of selected vehicles from the first main track to the second main track.

The first signalling means may include a first inductive signalling cable incorporated in or mounted on the first main track, the second signalling means may include a second inductive signalling cable incorporated in or mounted on the second main track, and the third signalling means may include a third inductive signalling cable incorporated in or mounted on the junction track. The said further means may include an extension of the second inductive signalling cable incorporated in or mounted on a part of the junction track. The further means may also, or alternatively, include a connection for applying control signals of the second signalling means to the third signalling cable.

Preferably the system comprises a network of main tracks and a plurality of intersections for connecting different pairs of the main tracks, each of the intersections comprising a junction track associated with equipment comprising vehicle detector means, a third signalling means and computer means for controlling vehicles on or approaching the junction track. Preferably for control purposes the system is operationally divided into parts, wherein each part includes one intersection with associated equipment as hereinbefore specified, and is capable of substantially self-sufficient operation without reference to the computer means and vehicle detectors in other parts of the system; hence a standard form of computer means can be provided for each part, regardless of the size and complexity of the system as a whole.

In a typical part of such a system which includes a junction track by which vehicles may be driven from a first main track to a second main track, a length of the junction track may be designated as queueing space sufficient to accomodate a predetermined maximum number of vehicles Q, the vehicle detector means will include a first vehicle detector for ascertaining the destination of each vehicle on the first main track as it approaches the junction where the junction track diverges from the first main track, and the computer means may include means for maintaining a record of the number q of vehicles currently allocated to the queueing space, maintaining a list of turn priorities for given destinations, and allocating to each vehicle a turn priority selected from the list according to the destination of the vehicle, comparing the allocated priority with the number q, and sending turning command signals to any vehicle which is allocated a turn priority greater than q, provided that q is less than Q. Alternatively or additionally the computer means may be arranged to send signals to prevent any vehicle which is allocated a priority less than q from turning on to the junction track.

The list of turn priorities for given destinations in each computer means will generally be predetermined according to the relative positions of the destinations concerned, relative to the intersection controlled by the computer means. Thus a zero turn priority will generally be given for any destination which can be reached in minimum time by continuing on the first main track past the intersection. A high turn priority will be given for any destination if turning at the controlled intersection will lead the vehicle on a significantly shorter route to its destination than a turn at any subsequent intersection; the priorities given will be in proportion to the saving in journey time involved. However, the computer means may include provision for modifying the list of turn priorities in response to signals from computers in other parts of the system, or from a central control. For instance, at an intersection where vehicles may turn left, some of the turn priorities may be temporarily increased in response to signals indicating congestion at the next intersection allowing a left turn; and signals indicating a temporarily obstructed line may be arranged to increase most of the turning priorities by an amount related to the number of opportunities for avoiding the obstruction which exist in the network between the obstruction and the intersection controlled.

In systems in which vehicles are moved independently over predetermined tracks, it is common practice to divide the tracks notionally into sections which may be marked or identified in various ways, and to determine or refer to the present locations of vehicles in the system by reference to the sections. In a novel control system which is preferred by the applicant, each vehicle is allocated to and associated with a section of track, hereinafter called a slot, in which it can come to rest safely; each moving vehicle in such a system will therefore be allocated to a slot in advance of the vehicle's actual position by an amount depending on the speed of the vehicle. The nature and advantages of such a system are explained in co-pending patent application Ser. No. 186,754, now U.S. Pat. No. 3,790,779, which is incorporated herein by reference.

EXEMPLARY DESCRIPTION

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, of which:

FIG. 1 is a schematic diagram, or map, of an idealized transportation system,

FIG. 2 is a diagram of a transportation system designed to suit an actual environment,

FIG. 3 is a schematic, larger scale diagram or map of a typical intersection of a system as shown in FIG. 1 or FIG. 2,

FIG. 4 is a schematic, larger scale diagram or map of a typical loading and unloading station,

FIG. 5 is a schematic circuit diagram of apparatus provided in each vehicle,

FIG. 6 is a diagram of a model track used in experimental trials of the system and

FIGS. 7A and 7B are flow charts illustrating the computer functions used to control the intersection of FIG. 3.

FIG. 1 shows an idealized network of one-way tracks, for vehicles running in the direction of the arrows; the dots indicate stations where vehicles may be loaded or unloaded, preferably in side-tracks which the main track by-passes as described hereinafter with reference to FIG. 4. Where two tracks cross at right angles, for instance at X in FIG. 1, it should be understood that the tracks will be at different levels, and traffic on either track will not interfere with traffic on the other; however at every crossing two one-way junction tracks (shown as arcs, for instance J) are provided, to enable vehicles to transfer from one track to the other. The network shown comprises two loops elongated in a north-south direction, crossing two loops which are elongated in an east-west direction, with two junction tracks at each crossing. Clearly a network of this kind, where journeys may start and finish at any desired stations, and any route consistent with the one-way restrictions may be followed, offers a versatile and effective transportation system suitable for urban transport, and may be extended as required by prolonging some of the loops or adding more loops. Clearly the network could be distorted to conform to topographical features and transportation needs.

It may be noted that while the system of FIG. 1 is clearly only a simple example of the kind of system conceived as suitable and desirable for satisfying urban transport demands, it is considerably more complex than any systems known to have been operated with a high utilization factor on a completely-scheduled control scheme; it is thought that the number of junctions involved even in this scheme would probably make a completely-scheduled form of control become difficult or unsatisfactory with a utilization factor of the order of 25%.

FIG. 2 shows schematically the main tracks of a hypothetical network planned, as part of an assessment study, to satisfy transportation needs in an actual city area; junction lanes would also of course be provided, as in FIG. 1 for instance, but they have been omitted from FIG. 2 for the sake of simplicity. The squares on FIG. 2 represent loading and unloading stations of the kind shown in FIG. 4. FIG. 2 is presented solely as an illustration of the degree of complexity and versatility which is contemplated and is considered to be made feasible by the present invention.

FIG. 3 shows a plan view of a typical intersection where a southbound track T1 crosses an eastbound track T2, including a junction track T12 and associated equipment for allowing and controlling cars required to go from the track T1 to the track T2. The broken lines on the tracks represent inductive signalling cables which are incorporated in, or mounted on, the structure of the tracks. A signalling cable S1 is mounted on the track T1 and is extended into the entrance end of the junction track T12, up to a point P3 such that the rear of any vehicle reaching P3 will be clear of the track T1. The cable S1 is connected to receive vehicle control signals from a transmitter TX1. Another signalling cable S2 is similarly mounted on the track T2 and is extended some way into the exit end of the junction track T12, up to a point P5. The cable S2 is connected to receive vehicle control signals from a transmitter TX2. A third signalling cable S12 is mounted on a length of the junction track T12 between the point P3 and the point P5. A part of this length between points P4 and P5 is designated as queueing space. The cable S12 is connected to receive vehicle control signals from a transmitter TX12.

Five vehicle detector units, D1 to D5 inclusive, are coupled to more localized inductive signalling loops, which are mounted in vertical planes beside the tracks at various places. D1 is connected to a loop adjacent to the track T1 between points P1 and P2 upstream from the place where the junction track T12 diverges from the track T1; D2 is connected to a loop adjacent to the track T12 near to the point P3; D3 is connected to a loop adjacent to the track T12 downstream from the point P3; D4 is connected to a loop adjacent to the track T12 near the point P5, and D5 is connected to a loop adjacent to the track T2, at a point P7 upsteam from the point P6 where the track T12 merges with the track T2. A computer C12 has input connections (not fully shown) from the transmitters TX1, TX2 and the vehicle detector units D1 to D5 inclusive, and has output connections for sending control signals to the transmitters TX1, TX2, TX12 and the vehicle detector units D1 to D5. The outgoing and returning conductors of the signalling cables S1, S2 and S12 are crossed over at regular intervals, so that receiving apparatus in each vehicle can check on the progress of the vehicle by detecting and counting phase reversals which occur in the signals induced in the receiving apparatus whenever the vehicle crosses a signal cable crossover, according to a known technique in the art. It should be understood that FIG. 3 is schematic and not drawn to scale.

In operation of the system, vehicles will proceed southbound on the track T1 and eastbound on the track T2. The vehicles on the track T1 will normally proceed at a steady rate governed by the repetition rate of pulses applied to the cable S1 by the transmitter TX1, and the vehicles on the track T2 will normally proceed at a steady rate governed by the repetition rate of pulses applied to the cable S2 by the transmitter TX2. The pulses from TX1 may be quite independent of the pulses from TX2, and in general there need not be any kind of synchronization between the two pulse trains, although they may have the same nominal repetition rate and for the sake of convenience they may be derived from a common source in some way which could give them a predetermined relative timing.

The vehicles which use the tracks of the system herein described will each carry receiver apparatus for receiving signals from the signalling cables (for instance S1, S2, S12) in the track on which it runs, and control apparatus for controlling the speed of the vehicle in response to these signals; details of suitable control apparatus are given in the aforesaid U.S. Pat. No. 3,790,779. The control apparatus is arranged to count slot-increment command pulses received via the signalling cables, to count pulses generated in the vehicle when it passes marker devices in the track (including the crossovers of the signalling cables hereinbefore mentioned, but possibly also or alternatively including marker devices of some other type not shown) and to derive a signal called a position-lag signal which is adjusted according to the difference between the results of the two counts. The control apparatus includes a servo-system for controlling the speed of the vehicle, so that the position-lag signal bears a predetermined relationship with the speed of the vehicle and corresponds to the distance required to decelerate the vehicle to a stop safely and satisfactorily. In the planning and operation of the transportation system as a whole, and in the control of all the vehicles travelling over a typical intersection of the kind shown in FIG. 3, each vehicle is notionally associated with a slot or part of the track in which it can safely be brought to rest if the signals from the signalling cables cease to be received; thus each vehicle is associated with a slot which is in advance of the vehicle's actual position by a variable distance which depends on the vehicle's speed and is also therefore related to the current value of the vehicle's position-lag signal.

Each vehicle also carries apparatus for communicating data concerning the vehicle to any of the vehicle detectors such as D1 to D5 when it comes within range of the detector's inductive signalling loop. Thus when a vehicle comes to the point P1, signals representing its destination and the present value of the position-lag signal in its control apparatus are sent to the detector D1 and thence to the computer C12. The signals may also indicate a serial number of the vehicle, and the time of its arrival at P1 may also be sent to the computer C12.

The length of the track T12 between P4 and P5 is designated as permissible queueing space and is sufficient to hold a predetermined number of vehicles Q. The computer C12 is arranged to maintain a record of at least the total number q of vehicles currently associated with the slots (that is to say track lengths for one vehicle) which comprise the queueing space, and also to maintain what is effectively a tabulation of a set of turning priorities appropriate for vehicles intended for various destinations at the intersection controlled by the computer C12. The tabulation of turning priorities is initially set with predetermined values according to the positions of the destinations relative to the position of the controlled intersection in the network or tracks; it may be modified from time to time in response to signals from other computers controlling other intersections, or from a central control station.

GENERAL DESCRIPTION OF CONTROL ACTIONS AT AN INTERSECTION

When the computer C12 receives signals from the detector unit D1 indicating the arrival of a vehicle at P1 and indicating the desired destination of the vehicle, it selects a corresponding turn priority from the tabulation, and compares it with the number (q) of vehicles currently associated with the queueing space slots. If the selected turn priority is greater than q, and q is less than Q, the computer sends a turning command signal to the vehicle, either through the transmitter TX1 and cable S1 or through the detector unit D1. Signals representing the serial number of the vehicle may be sent as a part of the turning command signal to ensure that the turning command will be obeyed only by the vehicle for which it is issued; alternatively if the signal is sent through the inductive loop connected to the detector D1 the serial number may be omitted if the loop is so short that there is no chance of its signals being received by another vehicle, the computer action taking less time than the vehicle will take to pass the loop. If the selected turn priority is less than q, or if q = Q indicating that the queueing space is fully allocated to vehicles ahead of the vehicle now being considered, the computer will send a go-straight-on command signal to the vehicle to prevent it from turning on to the junction track T12.

The turning or prevention of turning is controlled by the placing of guide wheels on the vehicle; each vehicle has two left-side guide wheels which can be engaged with the left-hand side of the track, and two right-side guide wheels which can be engaged with the right-hand side of the track, mechanically interlocked so that they cannot engage both sides of the track at once. A preferred construction for these guide wheels is described in a co-pending patent application Ser. No. 254,778, which is incorporated herein by reference. In the case of the intersection shown in FIG. 3, where the junction track T12 diverges from the left-hand side (as seen looking forward from a vehicle going southward on the track T1), the vehicle should engage its left-side guide wheels with the left-hand side of the track in response to a turning command signal, and this will cause it to follow the left-hand side onto the junction track T12. On the other hand, a go-straight-on signal should cause engagement of the right-side guide-wheels and cause the vehicle to follow the right-hand side of the track T1 past the intersection. A vehicle which goes straight on will remain and continue under the control of the pulses from the transmitter TX1, at least until it comes to another intersection where it may be directed to turn towards its destination.

When a vehicle has turned on to the junction track T12, it continues to receive signals from the cable S1 until it is clear of the track T1; then the serial number of the vehicle and the present value of its position-lag signal is communicated via the detector unit D2 to the computer C12. These signals are used to confirm that the vehicle has turned safely and is clear of the track T1; if they are not received within a predetermined time, the computer C12 may act to cause the signals on the cable S1 to be interrupted, at least locally, in case the vehicle is blocking the junction. The signals from D2 are also used to confirm, or correct if necessary, the computer's record of the slot associated with the vehicle. At this point P3 or thereabouts the vehicle leaves the region controlled by the cable S1 and comes onto the region controlled by the cable S12.

The speed control signals used in the system may be of several alternative types, namely specific signals, group signals, or general signals. The specific signals contain a code indicating the number of the vehicle for which they are intended, and only the vehicle concerned will respond to them. The general signals will, on the other hand, be acted upon by all vehicles which receive them; they may have a similar form to the specific signals but with a code representing "all vehicles" instead of a vehicle serial number. The group signals contain another code word, and will be acted upon by vehicles which have been made responsive to that code word. Thus a specific signal may be sent to a particular vehicle to cause it to switch into a mode responsive to group signals containing a particular code word, either for a specified number of signals, or until a further specific signal is caused to cancel the arrangement. Signals sent on the main track signalling cables such as S1 and S2 will usually be general signals, whereas more specific signals will be required on the signalling cables in the junction tracks (S12 for instance). Group signals may be used to reduce the number of specific signals which have to be sent.

The signals sent by the transmitter TX12 via the cable S12 will be varied under the control of the computer C12 to govern queueing actions which may be required on the junction track between P3 and P5. The need for queueing actions on the junction track and the amount of delay involved will clearly depend on the occurrences of gaps in the traffic flow on the track T2. This traffic flow is monitored by the detector D5, which sends to the computer C12 an indication of the passage of each vehicle together with an indication of the current value of its position-lag signal, which is related to its speed. From these signals, the computer C12 discovers when a gap will occur at the merging point; more precisely, its action is to deduce when a slot at a predetermined part of the track S2 between P7 and P6 is not allocated to any vehicle; then it sends a specific signal via TX12 and S12 to any vehicle allocated to the slot at the head (exit end) of the queueing space, to make that vehicle responsive to general command signals on the cable S2, at an appropriate time to ensure that if the vehicle responds normally to the signals on the cable S2 it will match its speed to the speed of the vehicles on the track T2 and will arrive at the merger point in time to fit in to the gap in the traffic stream which corresponds to the un-allocated slot. (This action is more fully described in the next section). The detector D4 is provided to check that the vehicle has matched its speed and its timing is correct, and to initiate appropriate emergency action to stop the vehicle, or turn it on to an escape route (not shown) if these conditions are not satisfied.

The computer C12 causes suitable signals to be sent through the transmitter TX12 and the cable S12 to cause each vehicle arriving on the junction track to be allocated to the highest available (not already allocated) slot in the queueing space, and to add one to this allocation whenever a vehicle is enabled to leave the head of the queue. If continuous traffic on the track T2 does not allow a safe exit for a vehicle allocated to the head of the queue, that vehicle will come to rest in a specified slot-length of the track just before P5, and subsequent vehicles will come to rest in consecutive slot lengths behind it. On the other hand, if an opportunity for a safe merging into the traffic on the track T2 arises before the vehicle allocated to the head of the queue has actually come to rest, it will be made responsive to signals derived or relayed from the general command signals on the cable S2, and will proceed onto the track T2 without stopping on the junction track T12.

It should be noted that the system herein described does not interfere with, or modify in any way, the progress of the main streams of vehicles going straight on past the intersection on the main tracks T1 and T2; such vehicles proceed at speeds determined entirely by the signals from the transmitters TX1 and TX2 respectively, with no perturbations which could complicate the control required at subsequent intersections. The system has the advantage of being very simple to understand, simple to put into practice, and simple to analyze and yet it is very versatile and can be readily adapted to suit various situations. For instance it is not limited to any particular number queueing spaces, and the list of turning priorities and the arrangements for modifying this list in various circumstances can be altered as desired quite easily. One each main track, the traffic can be kept moving in a steady perfectly synchronous stream with vehicles leaving it and joining it at intersections, and if desired (for instance to minimize congestion in some area) the speed of any such stream can be reduced by reducing the repetition rate of the signals sent by the corresponding transmitter (eg TX1 or TX2), without requiring any specific adjustment of any merging operations which may be already in progress when the change is made.

This arrangement, with queueing spaces on the junction tracks, also has the advantage that the control of a junction track will correspond to the control of operations in the preferred form of station having platforms on by-passed tracks as hereinafter described, so that the control apparatus for an intersection may be basically similar to the control apparatus for a station. The development work on apparatus for intersection control will therefore assist the development of apparatus for station control, and the similarity makes the system easier to understand and control.

DETAILED DESCRIPTION OF COMPUTER ACTIONS

For a full description and appreciation of the simplicity and versatility of the system, it is desirable to consider in greater detail the actions by which the computer C12 keeps account of the vehicles in the area under its control and the track slots allocated to them. These are surprisingly simple. The tracks under the control of the computer C12 are notionally divided into slot lengths, which are given numbers for reference in the calculations. One slot length, at the merger point P6 for instance, is given an arbitrary number, and consecutive slot lengths on the tracks leading up to this point are given consecutive numbers leading up to this number. For instance a slot length beginning at P6 may be arbitrarily numbered 100, and if the length of junction track T12 from P2 to P6 comprises say 88 slot lengths, these slot-lengths from P2 to P6 may be numbered consecutively from 12 to 99. Similarly if the track T2 between P7 and P6 comprises say 52 slot-lengths, they may be numbered consecutively from 48 to 99. The queueing space between points P4 and P5 on the track T12 will comprise several slot-lengths; to make the illustration definite, suppose that they are slots 49 to 54 inclusive. (Note that there will be some distinct but similarly-numbered slots on the track T2, somewhere between P7 and P6.)

When a vehicle having a serial number v first comes within operating range of the inductive loop connected to the detector D5, it must be at a known position, say slot forty-eight on track T2, and the current value of its position-lag signal will indicate how far ahead of its actual position is the slot to which it is allocated, that is to say the slot in which it will come to rest if it receives no more control signals. The detector D5 will send to the computer signals indicating the serial number v and the current value of the position-lag signal g; the computer will then in effect make a record of the number v associated with the allocated slot number, in this case (48 + g) since the detector is at slot forty-eight. As the vehicle advances on the track T2, its speed will be controlled so that its slot allocation increases in accordance with a count of slot-incrementing signals which it receives from the line S2; the computer C12 also receives these signals, and adds one to the allocated slot number stored in its record for each vehicle which should respond to the signal.

Thus the computer C12 in effect creates a tabulation of the serial numbers and slot allocations of vehicles on the track T2. Each entry in this tabulation is initiated by signals v and 48 + g when the vehicle concerned passes D5; thereafter the slot allocations are incremented appropriately according to the signals on the cable S2. When a vehicle passes the point P6, the entry relating to it may be discarded. The signals on the cable S2 will normally be general signals, to which every vehicle on the track will respond in the same way, and clearly general signals should cause all the slot allocations in the tabulation to be equally incremented.

Similarly the computer also creates another tabulation of the serial numbers and slot allocations of vehicles on the track T12, in which each entry may be initiated or confirmed by signals from the detector D2, and the slot allocations are appropriately incremented in accordance with the control signals transmitted to the vehicles either through the cables S1, S12, S2 or through the detector units and their inductive signalling loops. The incrementing in this case will be slightly more involved, as specific signals will be and group signals may be involved; clearly a specific signal for a particular vehicle should only affect the entry for that particular vehicle, and a group signal should only affect the entries for vehicles which have been made responsive to the group code contained in the group signal. Specific signals which may be used to make particular vehicles responsive to, or non-responsive to, a given group code should also operate logic circuits to make the corresponding tabulation entries liable or not liable to incrementing by group signals including the given group code. (It should be noted that the system could be operated with specific signals and general signals only; the arrangements required for dealing with group signals should be regarded as an optional complication which may or may not be adopted in any particular embodiment or intersection in the system).

The tabulation relating to vehicles on the track T12 will clearly show how many vehicles are allocated to slots between P3 and P5 or to slots between P4 and P5; either of these numbers may be taken as the number q hereinbefore mentioned, depending on whether the track between P3 and P4 is regarded as permissible queueing space or as space which should not normally be used for queueing. The slot at the head of the queueing space (at P5) will have a known number, say fifty-four in this case. When this slot is not already allocated to a vehicle, the computer should send specific signals via the transmitter TX12 and the cable S12 to the leading vehicle on the track T12 (that is to the vehicle with the highest slot allocation less than fifty-four), to increase its slot allocation to fifty-four. The computer should then send specific signals to the next vehicle to increase its slot allocation to fifty-three, and so on.

The length of track between P5 and the point P6 where the tracks T12 and T2 begin to merge together must be at least long enough to ensure that, if a vehicle is initially at rest at the point P5 and is then enabled to receive and respond to the general signals on the cable S2, it will reach a steady speed corresponding to the rate of these general signals (and therefore matching the speed of the traffic on track T2) before it reaches the merge point P6, indeed sufficiently in advance of the merge point P6 to enable this matching to be checked and to enable emergency stopping or diverting action to be taken before the merge point is reached if the matching is unsatisfactory. It follows that any vehicle which is made responsive to the general signals on the cable S2 when it is allocated to any slot up to P5 should in response to those signals match the speed of the traffic on T2, and if its tabulated slot allocation is incremented according to the signals on S2, this tabulated slot allocation should represent a slot ahead of its actual position by an amount corresponding to the rate of the signals on S2 and equal to the position-lag distances of the vehicles already on the track T2, before it reaches the merge point P6. It follows that successful merges can be arranged by making any vehicle allocated to slot fifty-four on the track T12 responsive to the general signals on the line S2 when and only when the corresponding slot fifty-four on the track T2 is not allocated to any vehicle. Hence the computer will be arranged so that when the tabulation of vehicles on T12 contains an entry for slot fifty-four and the tabulation of vehicles on T2 does not contain any entry for slot fifty-four, it will send a specific signal to the vehicle indicated in the entry for slot fifty-four of track T12, to make it responsive to the general signals on the cable S2 (if it is not near enough to S2 to receive these signals directly, but they can be relayed to it via TX12 and T12 -- the preferred arrangement is described hereinafter). At the same time, the computer should add an entry for this vehicle to the tabulation of vehicles on T2, to mark the place allocated to it in the traffic stream on T2. The next signal on S2 increments the slot allocation of the vehicle, making slot fifty-four on the track T12 available for the next following vehicle; the computer will then send specific signals or a group signal to increase the slot allocations of the queued vehicles by one, thereby advancing the queue.

In the preferred arrangement for providing general signals, group signals and specific signals, and for controlling the responsiveness of the vehicles, every signal sent to a vehicle contains an address part and a function part. The address part may be either the serial number of a specific vehicle, or one of two alternative group code words. The receiver apparatus in each vehicle contains decoder circuits for detecting and responding to only those signals with appropriate address parts. These circuits include a bistable circuit which can be set to a one state or reset to a zero state by given signals, and gate circuits operated by the bistable circuit, connected so that when the bistable is set the gate circuits will respond to and pass signals containing a first one of the two group code words, and when the bistable is reset the gate circuits will respond to and pass signals containing the second group code word. All general signals on the cable S2 will contain the first group code word, and will therefore affect all vehicles whose decoder bistable circuits are set. Any one of the following commands may be represented by a corresponding instruction code word in the function part of a signal:

select right guide wheel

select left guide wheel

transmit data (Including vehicle serial number and its current position-lag)

reset controller counters

set decoder bistable

reset decoder bistable

count one slot increment command pulse

The receiver apparatus is constructed to distinguish the instruction code words and initiate the appropriate response to each command.

As shown in FIG. 5 it includes a receiver 51 for detecting signals transmitted by the inductive signalling cables and by any of the vehicle detector units and local signalling loops within range. The signals are converted from serial to parallel form by a conventional converter 52 and are applied to address detector circuits 53 and instruction decoder circuits 54. These are simple logic circuits, responsive to signals representing prescribed codes or numbers.

Outputs of the address detector circuits are connected to inhibit or enable the instruction decoder circuits 54. Separate outputs from the instruction decoder circuits control guide wheel actuators 55, a data transmitter 56, the speed control apparatus 57, and the bistable circuit 58. The speed control apparatus 57 provides the data transmitter 56 with a digital position-lag signal, and the bistable circuit 58 has outputs connected to control two of the address detector circuits 53. A third address detector circuit is set to enable the instruction decoder circuits to respond to any specific signals including the prescribed serial number of the individual vehicle.

When a vehicle enters the junction track it is sent a signal to reset its bistable circuit, thereby inhibiting it from any response to the general signals which are relayed from the cable S2 (or transmitter TX2) on to the cable S12. When it can safely be allowed to leave the queueing space and proceed to the merge point P6, it is sent a signal to set its bistable circuit once more, thus making it again responsive to the general slot-incrementing command signals.

If the detector D5 should detect the passage of a vehicle having a position-lag signal substantially different from the value of position-lag which should correspond to the rate of the general signals on S2, it should act to inhibit any mergers on the track T2 and divert the vehicle concerned to a maintenance area.

Clearly the actions required to control turns, queueing, and mergers, as hereinbefore described, have been shown to require only simple logical procedures, and the maintenance of the slot allocation lists requires only a list processing procedure, of a kind known in the data processing art, so that it is unnecessary to describe them in any further detail. A suitable program for performing the described actions in a satisfactory sequence is represented by the flow charts FIGS. 7A and 7B.

The reliability and safety of the system can clearly be increased by incorporating redundant components, providing a separate monitoring system, and other established techniques. The detectors D3 and D4 may be regarded as optional; if provided, they may be used as a part of a monitoring system. The signals need not be transmitted by inductive signalling loops and cables as described; clearly any other convenient means for signalling to moving vehicles on predetermined tracks could be used. Leaking wave guides or transmission lines, conductor rails, or optical signalling apparatus could be utilized. Instead of forming a tabulation of vehicle numbers and slot numbers, the computer could have a store in which one address is allocated for each slot in the length of track controlled; each vehicle number can then be entered at an appropriate address, and moved from one address to the next whenever the slot allocation of the vehicle is incremented.

PREFERRED FORM FOR STATIONS

As hereinbefore mentioned, stations in the system are preferably provided on sidings which are by-passed by the main track, so that the main traffic stream may be unaffected by loading and unloading operations. FIG. 4 shows a plan view of the arrangement of a typical station and equipment associated with it. The station is served by a track TP which leaves and rejoins the main track T1. At a point P10 the track TP divides into two parallel tracks serving separate platforms P1 and P2; each of these tracks comprises a deceleration length DN and an input queue space IQ. The two parallel tracks merge into one at a point P11 beyond the platforms and continue forming an output queue space OQ between points P11 and P12 and an acceleration length AN before rejoining the main track T1 at P13. A transmitter TXP is connected to signalling cables (not shown) mounted on the track TP between P10 and P12. Detector units D11 and D15 inclusive, the transmitter TXP, the signalling cable S1 (not shown in FIG. 4, but mounted on the track T1) and ticket transducers and other monitoring devices (not shown) installed on the platforms P1 and P2 are all connected to a computer CP which will monitor and control vehicles on the track TP. The detector unit D11 is on the main track T1 upstream from the divergence of the track TP; D12 is on track TP upstream from P10; D13 and D14 are on the two platform tracks at the beginning of their deceleration lengths; and D15 is on the acceleration length AN. Clearly the operation of a station track may have many features in common with the operation of a junction track. Signals from D11 are used to form a tabulation of the vehicles passing on the main track; other signals from D11 indicate any vehicles whose destination is the station shown -- such vehicles should be sent a turning command signal unless the input queueing spaces are fully allocated already. A tabulation of the vehicles on the station track TP is derived from signals from the detector D12. At P10, vehicles may be directed to whichever platform track has more unallocated slots at its platform and in its input queue, or may be directed to form batches for the two platforms alternately. Specific signals are initiated and sent via the transmitter TXP to allocate vehicles to the highest available places in the input queue and at the platforms. When a vehicle has been allocated to the platform slot at which it is to stop, its allocation will not be increased until it has come to rest at the allocated platform slot, time has been allowed for unloading and reloading, and a positive indication has been received indicating that the vehicle is in a ready-to-go condition with all doors closed.

Vehicles may be loaded and given new destinations (for instance by inserting a ticket in a ticket transducer device) at the platform slot; alternatively control signals from a central control may be communicated to empty vehicles, to cause them to leave for other stations where the demand for vehicles is liable to exceed the number of vehicles available. It is arranged that a vehicle departure from platform P1 will temporarily inhibit any vehicle departure from platform P2 and vice versa, to prevent collisions at P11. Vehicles leaving the platforms are given signals sufficient to allocate them to the highest available slot (that is the slot nearest to P12) in the output queue. The main signalling cable of the main track T1 (not shown in FIG. 4) is extended from P13 up the station track TP to the output queue region, and as in the case of a junction track a vehicle allocated to the head of the output queue is transferred to the control of this signalling cable when a corresponding slot on the main track is not allocated. Like the detectors D3 and D4 in FIG. 3, the detectors D13, D14 and D15 may be regarded as optional, and if they are provided they may be used as part of a monitoring system.

EXPERIMENTAL TRIALS

The operation of an intersection as hereinbefore described with reference to FIG. 3, and the operation of a simple station with only one platform track has been checked by running model vehicles on a model track under the control of a Honeywell type 316 computer. To save space and expense, the model track was formed as shown in FIG. 6. For the experiments relating to the operation of a station this was treated as a station like FIG. 4 but with only one platform track, with the tracks T1 and TP curved to form an almost complete oval and the track at P13 connected by a short length of track to the track at D11. For the experiments relating to the operation of an intersection, the model track was considered equivalent to an intersection like a mirror image of FIG. 3 with the south end of T1 connected to the west end of T2 and the east end of T2 connected by a short length of track to the north end of T1. Thus on the model the outer track is the main line, and the inner track is the platform track in station experiments or the junction track in intersection experiments. The computer was controlled by the program given in the Appendix to this specification; this is written in the Honeywell DAP-16 language, which is described in Honeywell Document No 130071629, M-1018 "DAP-16 Manual" (December 1966). Persons skilled in the art will realise that some of the instructions in this program relate to parameters of the model track such as the number of slots and the positions of the vehicle detectors, but clearly any real intersection or station could be controlled similarly.

ACKNOWLEDGEMENT OF NEAREST KNOWN PRIOR ART

The nearest prior art known to the Applicant is contained in two papers "Automated Network Personal Transit Systems" by H. Bernstein, and "Development Simulation of an Urban Transit System" by A. V. Munson Jnr, and T. E. Travis, of The Aerospace Corporation, El Segundo, Calif.

The paper by Bernstein suggests some of the advantages of a transportation system using remotely-controlled vehicles on prepared guideways, each guideway being used by vehicles going in one direction only, with stations on siding lines. He states the desirability of running traffic at constant velocity on the main lines, and accelerating cars to this velocity on local access lines before merging them into gaps in the main traffic stream. He also suggests the use of local intersection computers to determine routing instructions for particular vehicles and to control manoeuvres required for traffic control according to information provided by wayside sensors located at the entry to the local computer's control zone. He suggests that routing instructions would be based on tabular information stored within the local computer for determining whether each car should turn or not, according to its destination, and that the routing instructions might be modified by signals from a central computer. These arrangements are represented in FIG. 6 of the drawings accompanying Bernstein's paper, which may be compared with the Applicant's FIGS. 1 and 3.

The paper by Munson and Travis describes a computer simulation of an intersection and traffic thereon in a system of the sort described by Bernstein. This clearly shows that, though there are some similarities between their conception and the applicant's system, there are also some differences of fundamental importance.

In the system of these prior papers, all manoeuvering adjustments of vehicle speeds required to allow traffic streams to merge safely are applied to vehicles on a main-line, non-turning track. The traffic on junction tracks apparently continues unchecked at a constant velocity, which must therefore be common to all the traffic streams in the system.

In this prior art system, the necessary manoeuvres are applied to vehicles in a main-line traffic stream; since this main-line traffic stream will comprise all vehicles bound for all subsequent intersections and destinations, one would expect it normally to comprise more vehicles than any typical sub-group of vehicles desiring to join or to leave the main track at a given intersection. The more congested a traffic stream is, the more difficult it is to apply manoeuvres to it without repercussions and the more likely it is that it will be impossible to form a gap at a desired point in the stream with allowable manoeuvering distance provided Munson and Travis' results, in their FIG. 2, show this to be a significant probability in practical conditions envisaged. It is noted from the latter part of their section 2.4 that the reported simulation did not adequately allow for vehicles which would be prevented from joining the main stream by the impossibility of forming a gap in the main line traffic to receive them immediately.

The applicant's system is thought to be simpler and more satisfactory because the main-line traffic does not need to be adjusted to allow mergers. The necessary adjustments are made in the traffic on the junction track, which will generally be less congested. By allowing opportunities for queueing on the junction track, the applicant's system allows more opportunities for mergers to be used and makes diversions less likely. It is more versatile since it does not require the speeds of traffic on the two intersecting main lines to be equal or to have any other specific relationship.

The disclosures referred to do not in any way suggest or anticipate the applicant's arrangement of signalling means claimed hereinafter, the applicant's arrangements for allocating vehicles to sections in which they may safely come to rest, the applicant's arrangements for allowing queueing on the junction tracks and comparing the tabulated turning priorities with the number of vehicles already allocated to the queueing space, or the applicant's use of group signals and receivers provided with decoder units. ##SPC1##

Claims

I claim:

1. A transportation system comprising a plurality of tracks and a plurality of remotely controllable vehicles constructed to run over the said tracks, wherein the said tracks comprise at least a first main track, a second main track, and a junction track by which vehicles may be driven from the first main track to the second main track, and the system also comprises first signalling means for sending control signals to vehicles on the first main track such that all vehicles on a continuous extended length thereof receive the same control signals to cause the said vehicles to proceed in a first regular traffic stream along the said first main track, means for sending signals to selected ones of the said vehicles to divert them on to the junction track, second signalling means for sending control signals to vehicles on the second main track such that all vehicles on a continuous extended length thereof receive the same control signals to cause the said vehicles to proceed in a second regular traffic stream along the said second main track, third signalling means for sending control signals to vehicles on the junction track to control their progress on the junction track and to make them responsive to signals derived from the second signalling means at selected times, further means for sending control signals derived from the second signalling means to vehicles on a part of the junction track to cause the said vehicles to match their speed to the speed of the said second regular traffic stream, a plurality of vehicle detector means for detecting the passage of vehicles on the first main track, the second main track, and the junction track and receiving data signals from the said vehicles, and computer means connected to the vehicle detector means and to the first, second and third signalling means for controlling the transfer of selected vehicles from the first main track to the second main track.

2. A transportation system as claimed in claim 1 and wherein the first signalling means comprises a first inductive signalling cable incorporated in or mounted on the first main track, the second signalling means comprises a second inductive signalling cable incorporated in or mounted on the second main track, the third signalling means comprises a third inductive signalling cable incorporated in or mounted on the junction track, and the said further means comprises an extension of the second inductive signalling cable incorporated in or mounted on a part of the junction track.

3. A transportation system as claimed in claim 1 and wherein the first signalling means comprises a first inductive signalling cable incorporated in or mounted on the first main track, the second signalling means comprises a second inductive signalling cable incorporated in or mounted on the second main track, the third signalling means comprises a third inductive signalling cable incorporated in or mounted on the junction track, and the said further means comprises a connection for applying control signals of the second signalling means to the third signalling cable.

4. A transportation system as claimed in claim 1 wherein the said control signals sent to the vehicles have address parts and instruction parts, and in each vehicle there is provided a receiver incorporating decoder means for distinguishing prescribed address parts and instruction parts, and vehicle control apparatus responsive to output signals from the decoder means for initiating a prescribed response to predetermined control signals.

5. A transportation system as claimed in claim 4 wherein the decoder means in each vehicle comprises a bistable circuit, means for setting the bistable circuit in response to a control signal comprising a prescribed specific address part specific to the individual vehicle and a first prescribed instruction part, means for resetting the bistable circuit in response to a control signal comprising the said specific address part and a second prescribed instruction part, and instruction detector means controlled by the bistable circuit responsive to the instruction part of any control signal whose address part is a first prescribed group address whenever the bistable circuit is set, and responsive to the instruction part of any control signal whose address part is a second prescribed group address whenever the bistable circuit is reset.

6. A transportation system comprising a network of main tracks and main track signaling means for signaling to vehicles on each main track so that all vehicles on a continuous extended length of any main track will receive the same control signals for causing said vehicles to proceed in regular traffic streams along said main track; the network having a plurality of intersections which each comprise a one-way junction track connecting two of the said main tracks and having intersection control means provided for each intersection capable of substantially self-sufficient operation for controlling vehicles approaching the junction track and on the junction track thereof; the junction track leading from a first main track to a second main track at each of said intersections, the first main track being equipped with first main track signaling means, the second main track being equipped with second main track signaling means, and the intersection control means comprising means for directing selected vehicles from the first track onto the junction track, third signaling means for sending control signals to vehicles on the junction track to control their progress and to make selected vehicles responsive to signals derived from the second main track signaling means at selected times, further means for sending control signals derived from the second main track signaling means to vehicles on a part of the junction track, a plurality of vehicle detector means for detecting the passage of vehicles on the first main track, the second main track, and the junction track and for receiving data signals from the said vehicles, and computer means connected to the vehicle detector means and to the first, second and third signaling means for controlling the transfer of vehicles from the first main track over the junction track to the second main track.

7. A transportation system as claimed in claim 6 wherein each vehicle is notionally allocated to a section of the track in which it may safely come to rest, and in each of the intersections a length of the junction track is designated as queueing space sufficient to accomodate a predetermined maximum number of vehicles Q and the intersection control means comprises:

a first vehicle detector means for ascertaining the destination of each vehicle and an indication of the section of track to which it is currently allocated as it approaches the entry to the junction track,

and computer means for maintaining a list of turn priorities for given destinations, allocating to each vehicle a turn priority selected from the list according to the destination of the vehicle, maintaining a record of the number q of vehicles currently allocated to the queueing space, comparing the allocated turn priority with the number q, and sending turning command signals to any vehicle which is allocated a turn priority greater than q if and only if q is less than Q, so as to direct the vehicle on to the junction track.

8. A transportation system as claimed in claim 7 wherein the first vehicle detector means comprises means for receiving a position-lag signal from each passing vehicle, which represents the distance between the actual position of the vehicle and the track section to which it is currently allocated, and the computer means comprises means for determining the track section to which the vehicle is currently allocated by adding the vehicle's position-lag signal to a signal representing the position of the vehicle when detected by the first vehicle detector means.

9. A transportation system as claimed in claim 8 wherein the computer means comprises means for maintaining a list of all vehicles currently allocated to sections of the junction track and the sections to which they are allocated, and a list of all vehicles currently allocated to neighbouring sections of the second main track and the sections to which they are allocated, and means responsive to the control signals sent through the said second and third signalling means to the said vehicles for incrementing the sections indicated in the said lists for the vehicles which should respond to the said control signals.

10. A transportation system as claimed in claim 9, wherein each main track has a signalling means for sending control signals to vehicles thereon to cause the said vehicles to proceed in a regular traffic stream along the main track, and each vehicle is notionally allocated to a section of the track in which it may safely come to rest, and the system also comprises a plurality of stations each having:

at least one platform track connected at both ends to a main track of the system,

first vehicle detector means for detecting each vehicle on the main track as it approaches the entrance end of the platform track, ascertaining whether it is desired to stop at the station and receiving an indication of the track section to which it is currently allocated,

means for sending a turning command signal to any vehicle which is desired to stop at the station to cause it to turn on to the platform track provided that the platform track is not unduly congested,

means for maintaining a list of vehicles continuing on the main track and a list of vehicles on the platform track, indicating the track sections to which the vehicles are allocated,

and means for rendering any vehicle desired to leave the station responsive to the signalling means of the main track at an instant when a predetermined section on the part of the main track between the two ends of the platform track is not allocated to any vehicle.

11. A transportation system as claimed in claim 8 wherein the computer means comprises means for maintaining a list of track sections on the junction track and track sections on the second main track indicating all vehicles currently allocated to the said track sections, and means for transferring vehicle indications in the said list in response to control signals sent through the said second and third signalling means to cause the vehicles to advance.

12. A transportation system as claimed in claim 8 wherein the computer means comprises means for sending a control signal to any vehicle allocated to a prescribed track section at the head of the queueing space to render to said vehicle responsive to signals derived from the second signalling means at an instant when a predetermined section of the second main track has no vehicle allocated to it.