"Apparatus and method for automatic logging of vehicles in motion."

TEXT OF THE DESCRIPTION

The invention relates to an apparatus for the automatic logging of vehicles in motion, with automatic exchange of data, in particular with automatic debit of tolls, comprising: - at least one automatic, fixed, transceiver station which is provided with local computation and control means for the transmission and recep¬ tion procedures and for identifying the users -and calculating the tolls to be debited to each identified user, which fixed station is located at a specified point on a vehicular travelway; an on-board transceiver unit for each vehicle, which on-board unit is provided with computing and control means of the transmission and recep- tion procedures, as well as user or vehicle identifier means and means for recording the debited toll; the fixed station and each on-board unit being able to communicate bidirectionally on command from the said fixed station, in order to exchange data, for example relating to the user and to the debited toll, during transit of the on-board unit through the area of the travelway covered by the

field of action (area of coverage) of at least one antenna of the fixed station, the fixed, transceiver station having a plurality of transceiver antennae located above the vehicu- lar travelway and oriented towards the latter, at a height greater than the maximum height of the vehicles, which antennae are distributed transversely to the travelway and are made in such a way as to each generate a limited area of coverage on the underlying travelway, the said areas of coverage being located alongside each other in the direction transverse to the travel¬ way, while each area of coverage has a width and a length of relatively small dimensions with respect to the plan dimensions of the vehicles and such as not to contain more than one on-board unit at a time and hence to communicate with not more than one on-board unit at a time and the computing and control means being able to compute separately from one another the reception and transmission signals of each antenna

An apparatus of this type is known for example from Patent Application EP-A-0585718 of the same prop- rietor. In this apparatus, despite the presence of areas of coverage for the activation of the on-board trans¬ ceiver units, typically so-called transponders, which are located upstream of the areas of communication, the danger remains that an on-board unit will be able to communicate with the communication antennae even before it has penetrated into the area of communication of same. In particular this may include the leapfrogging of the

communication from on-board units correctly positioned in the areas of communication by on-board units of following vehicles which have not yet penetrated into the said areas of communication. These errors generally occur when for example the signals received by the on-board unit in the area of coverage of communication become attenuated to the same level as the signals receivable by the on¬ board unit in the area of coverage of activation or simply outside the area of coverage of communication for which the latter responds first to the communication. In particular two critical cases are noted in which these effects occur:

- the vehicle following is for example not fitted with a windscreen (motorbike) and responds before entering the area of communication;

- the vehicle following can respond prior to entry into the area of communication by virtue of a signal reflec¬ tion caused by the presence of the metallic mass of the vehicle in front. This effect includes appreciable levels of error and is particularly detrimental when the transaction over the ether is associated with an apparatus for the optical logging of vehicles and of their position with which images are recorded of vehicles erroneously or unlawfully speeding through the barrier.

The purpose of the invention is to produce an apparatus of the type described initially, in such a way that with simple and inexpensive expedients it is possible effectively to overcome the drawbacks above. The invention permits the above purposes with an apparatus of the type described initially, in which means are provided in order to blind the on-board units which

are still outside the strip of areas of coverage for communication, in relation to reception of the communi¬ cation signals transmitted by the communication antennae, so-called jamming means. Advantageously, jamming means are activated in such a way as not to cause disturbances to the communica¬ tion between the on-board units in the areas of communi¬ cation and the corresponding antennae.

When the apparatus is provided with one or more additional activation antennae for the on-board trans¬ ceiver means which form a strip of areas of coverage of activation ahead of the strip of areas of coverage of communication, with reference to the direction of pro¬ gress of the vehicles, and which operate at a frequency different from that of the communication antennae, the blinding or disturbance of reception of the communication signals by the on-board units which are still in the area of coverage of activation is obtained by choosing the working frequency.of the areas of activation and/or the transmission power of the activation signals within such a band and of a level such as to disturb, rendering the signal of the communication antennae unreceivable and/or unintelligible.

The invention also relates to a particular method of operatdLng the aforesaid apparatus, according to which the antennae are divided into two groups, each of which groups forms two rows of areas of coverage, the areas of coverage of one of the two groups being intercalated with those of the other group, while the antennae of one group are activated in radio communication alternately with those of the other group respectively for a fraction of a period of the overall activation time.

To preclude interference between the antennae of each group, the antennae of each group use two different reception/transmission frequencies, the said frequencies being distributed alternately, within the compass of each group, to the corresponding antennae, while the fixed station and the on-board units are of the type able to transmit and receive at the said two frequencies.

The two frequencies are distributed alternately to the antennae of the two groups, in such a way that the area of coverage relating to the antenna of one of the two groups operates at the same frequency as the area of coverage directly alongside relating to an antenna of the other group of antennae.

According to an enhancement, the local computa- tion and control means are provided with analysis means for the response signals from the on-board units which check the formal correctness of the said signals, allow¬ ing, in the extremely rare eventuality that two on-board units come into confliσt within the compass-of a single area of coverage of an antenna, authorization of the communication of a single thereof, when the interference due to the other on-board unit is of a level such as not to compromise the intelligibility of the response signal from the first on-board unit, while communication is blocked for both on-board units in the case of unintel¬ ligible response signals.

By virtue of the above expedients, the apparatus and the method according to the invention allow the execution of the automatic debit with the transit in parallel of several vehicles, without the latter having to travel in a column on a single-carriageway lane. The areas of coverage may be suitably dimensioned in such a

way that, taking into account the minimum possible dimensions of the vehicles and the minimum distance between them, communication can be authorized for a single on-board unit at a time within the area of coverage of an antenna of the fixed station. In this case, the on-board units of two vehicles approaching the fixed station side by side in fact communicate, with very high probability, with two different antennae thereof. This makes it possible to avoid the exacting procedures of parallel transmission, keeping down the costs of the fixed station and above all of the on-board units. Furthermore, the jamming means make it possible to render the incidence of communication errors very low. The subsequent enhancements make it possible to limit to a minimum the possible interferences between the communi¬ cations either within the compass of two adjacent areas of coverage or in the case in which two on-board units come into conflict in one area of coverage.

By suitably setting the inximiiB speed of travel on the basis of guaranteeing coαplete execution of the transmission procedures between the fixed station and the on-board unit within a fraction of a period, during which a single group of antennae is active, it is possible appreciably to reduce the possibilities of communication errors to an infinitesimal value.

Furthermore, on the basis of the area of coverage in which the communication took place it is possible to determine to a certain approximation the position of the vehicle. According to an enhancement, the radio communica¬ tion apparatus can be associated with a video apparatus for logging the presence of a vehicle in the station. The

video logging apparatus is provided with means for identifying the position of the vehicle and with computer/correlator means for the position logged by means thereof with respect to the position of the vehicle as logged using radio communication.

This makes it possible to determine if a vehicle without an on-board unit has sped through the fixed station or if the communication with the corresponding on-board unit did not take place correctly, resulting in no debit of toll.

Preferably, the fixed station comprises two gates with each of which are associated two groups of trans¬ ceiver antennae of the above type. In this case, the transaction communications are executed in two successive phases respectively corresponding with the first and with the second gate. In this way it is possible to provide for greater maximum speeds of travel, further limiting the length of the areas of coverage. Furthermore the apparatus is capable of operating correctly also- in the case in which, at the fixed station, the vehicles exhibit transverse components of motion, or execute changes of carriageway.

The method according to the invention makes provision for one on-board unit to be able to communicate with more than one antenna.

The invention also addresses other characteris¬ tics which further enhance the apparatus and the method above and which are the subject of the claims below.

The characteristic features of the invention and the advantages deriving therefrom will emerge with greater detail from the description of a preferred embodiment, illustrated by way of non-limiting example in

698 _ PCI7EP9601385

8 the appended drawings in which:

Fig. 1 illustrates a highly schematic perspective view of the apparatus according to the invention, in which only one gate of the fixed station is indicated. Fig. 2 is a side elevational view of a fixed station according to the invention.

Fig. 3 is a front elevational view on the second gate of the fixed station according to Fig. 2.

Fig. 4 illustrates a transceiver antenna panel of the fixed station, according to an embodiment with modular construction.

Fig. 5 schematically illustrates the relative location of the areas of coverage obtained with the antennae of the fixed station according to the preceding figures.

Fig. 6 illustrates a block diagram of the elec¬ tronic circuit of the fixed station according to the preceding figures.

Fig. 7 illustrates a general block diagram of the apparatus according to the invention.

Fig. 8 illustrates a block diagram of the on¬ board unit.

Fig. 9 illustrates a block diagram of the elec¬ tronic control circuit associated with the first gate of the apparatus according to the preceding figures.

Fig. 10 is a block diagram of the control circuit associated with the second gate of the apparatus accord¬ ing to the preceding figures.

Fig. 11 is a block diagram of the electronic control circuit in respect of the part common to a station according to the preceding figures.

Figs. 12 to 15 illustrate a few examples of the

98 _g PCI7EP96/01385

operation of the apparatus according to the preceding figures, in the condition of maximum criticality.

Figs. 16 and 17 illustrate two views of a com¬ munication antenna for the generation of areas of coverage according to the preceding figures.

With reference to Fig. 7, an apparatus according to the invention comprises at least one fixed transceiver station which cooperates with on-board transceiver units 3 each associated with a vehicle. The fixed transceiver station comprises local computation and control means for the transmission and reception procedures and for ident¬ ifying the users and calculating the debits, which means are indicated overall as 1. The computing and control means 1 communicate via radio with the on-board trans- ceiver unit 3 by means of antennae A.l-A.n. Furthermore, by virtue of transmission means 2, these communicate with a central control unit 15, for example a central com¬ puter. The on-board unit 3 can be of the type operating in connection with a card 4, for example of the micropro- cessor or so-called smart-card type, by virtue of which the on-board unit 3 is supplied with the user identifi¬ cation codes to be transmitted to the fixed station for calculating the debit, and in which the debits calculated by the fixed station are recorded, which are transmitted by the latter to the on-board unit 3. The card 4 can store for example a certain prepaid sum, from which the amounts of the tolls debited by the fixed station are automatically deducted.

An example of an on-board unit 3 is illustrated in Fig. 8. The said unit has a transceiver antenna 5 to which an automatic activation device 6 is connected. The antenna 6 is connected to a transmitter 7 and to a

receiver 8 which in turn are connected to a control processor 10 across a coder/decoder 9. The control processor 10 commands a reader 11 of the card 4 in respect of the reading of the identification data and of the total residual credit recorded therein and in respect of the recording of the debit data, or the deduction of the debited sum from the total residual credit. Further¬ more a display 12 is connected to the control processor 10. The on-board unit 3 is powered by a sealed battery 13 and by a replaceable battery 14. The sealed battery 13 preferably powers the activation device 6, the coder 9, the receiver 8 and the transmitter 7, while the replace¬ able batteries 14 power the control unit 10, the display 12 and the write-read unit 11 for the card 4. With reference to Figs. 1 and 2, the fixed transceiver station is located at a specified point of a vehicular travelway, for example a road with a plurality of carriageways. The fixed station is made up of two gates, a first gate PI and a second gate P2, only the first gate PI being illustrated in Fig. 1. On the gantry of the gates PI and P2 a plurality of reception/trans¬ mission antennae A.l-A.n is supported, which are dis¬ tributed along an axis transverse to the travelway and are oriented facing the road surface of the carriageway. The on-board units 3 are indicated diagrammatically in Fig. 1 and are fixed for example to the windscreen of travelling vehicles or to the handlebars of motor cycles or the like.

The antennae A.l-A.n of each gate PI, P2 form fields of coverage C.l-C.n of length LI and width L2 decidedly smaller than the plan dimensions of the vehicles. In particular the antennae A.l-A.n are made in

698 PCIYEP96/01385

such a way as to generate an intersection of elliptical shape between the lobe of the antenna as measured at -3dB (with respect to the point of maximum radiation) and the plane parallel to the roadway passing through these points and which constitutes the actual area of coverage C.l-C.n, while any side lobes exhibit appreciably smaller signal levels. The elliptical areas of coverage C.l-C.n are located alongside one another in the direction transverse to the travelway, in such a way as to form a strip of coverage transverse to the travelway. According to Fig. 5, the centres of two adjacent areas of coverage are spaced apart to a smaller extent L3 than the width L2, in such a way that the areas of coverage C.l-C.n overlap in the lateral peripheral areas. The areas of coverage C.l-C.n are provided directly upstream of the respective gate PI, P2.

Advantageously the horizontal plane I, in which the areas of coverage C.l-C.n of the antennae A.l-A.n exhibit their logging dimensions, as above, is provided at a height L4 from the road bed corresponding substantially to a middle level, where the on-board units 3 in the different vehicles are located, for example at a height L4 = lm.

Each gate PI, P2, further exhibits activation antennae AT for the on-board units 3. The activation antennae AT are intended to transmit only signals for activating the on-board units 3, with which they command the activation device 6 of the on-board units and which generate areas of coverage CT, likewise elliptical, which are of broader dimensions with respect to the areas of coverage C.l-C.n and which form an activation strip upstream of the said areas of coverage C.l-C.n.

98 PCI7EP96/01385

12 Illustrated in Fig. 6 is a more detailed block diagram of the local computing and control means 1. The said means comprise radiofrequency transceiver means 20 for each gate PI, P2 to which are connected the corres- ponding antennae A.l-A.n and the activation antennae AT. The transceiver means 20 of each gate PI, P2 are com¬ manded by gate control units 21, 21' which are in turn controlled by a local control unit 22 of the station, with which they communicate via a bidirectional network 23 for example of the so-called LAN type. The local control unit 22 of the station communicates in turn via a multiplexer 24 and transmission means 2, for example a so-called modem or the like, with the central computer 15 (Fig. 7) . An embodiment of the gate control units 21, 21' and of the radiofrequency transceiver means 20 for the gates PI and P2 is illustrated in more detail in Figures 9 and 10. In this case, the embodiments illustrated refer to a modu-lar construction of the apparatus. With particu- lar reference to Fig. 4, the antennae A.l-A.n of each gate are distributed over a plurality of support panels 25. The support panel has eight antennae A.1-A.8 divided into two series, SI with the antennae A.1-A.4 and S2 with the antennae A.5-A.8. An activation antenna AT is associ- ated with the two series of antennae SI, S2. Illustrated in Fig. 5 are the relevant areas of coverage C.1-C.8 of the antennae A.1-A.8 and their reciprocal location.

The gate control units 21, 21' comprise a central control processor 121, 121' to which are connected memories 221, 221', a control facility 321, 321' for the activation antenna AT, a control facility 421, 421' for the transceiver means 20 and an interface for a communi-

cation network, for example a so-called Ethernet inter¬ face 521, 521', for communication with the local station control unit 22.

Corresponding to the modular construction of the 5 support panels of the antennae according to Fig. 4 there is a similar modular construction of the control facilities 321, 321', 421, 421' for the activation antennae AT and for the transceiver antennae A.1-A.8 and transceiver facilities 20. These facilities 321, 321',

10 421, 421' and 20 can be made with an expandable card construction, there being provided, for example, a transceiver facility 20 for the antennae A.1-A.8 and AT of each panel 25, and each control facility 321, 321' for the antennae AT and a control facility 421, 421' for the

15 antennae A.1-A.8 being capable of simultaneously controlling the transceiver facilities 20 of a number of panels 25. Illustrated in Figures 9 and 10 for simplicity is a single panel 25 of antennae A.1-A.8 and AT with the respective transceiver facility 20. Such a transceiver

20 facility 20 is made up of a transceiver module 120 for the series SI of antennae A.1-A.4 and AT of the panel 25 and a transceiver module 220 for the series S2 comprising the antennae A.5-A.8. The two modules 120, 220 both have a power supply 29 and two transceivers 26, 27. The trans-

25 ceivers 26 of each transceiver module 120, 220, operate at a first identical frequency fl, while the transceivers 27 operate at an identical frequency f2 different from that of the transceivers 26. The transceivers 26 are connected respectively to the antennae A.l, A.2 and A.5,

30 A.6, while the transceivers 27 are connected to the antennae A.3, A.4 and A.7, A.8. The transceiver module 120 associated with the first series of antennae SI

further exhibits a transmitter 28 which operates at a further different frequency f3 and is connected to the activation antenna AT.

The gate control units 21, 21* can be provided with means for analysing the response signals from the on-board units 3, picked up by each antenna A.n, for the purpose of logging the formal correctness of the response signals from the on-board units 3, allowing for example communication with a single on-board unit when two of them come into conflict within the area of coverage of one antenna and when in this case the intelligibility of the response signal from one of the said two on-board units is not compromised by the interference due to the response signal from the other on-board unit, for example because of a decisive difference in level of the said two signals.

The receiver 8 and the transmitter 7 of the on¬ board units 3 are of the type able to transmit and receive at the- two frequencies fl, f2 and at least to receive at the frequency f3.

The location of the antennae A.1-A.8 on the panel and the particular activation thereof at different frequencies fl, f2 determines the particular distribution of the areas of coverage with different frequencies from that of Fig. 5.

The frequencies fl, f2 and f3 are chosen in frequency fields which differ mutually to an extent such as to provide protection to the transmissions in both the transverse direction and in the direction of progress. In fact, cases may occur in which the signals from the communication antennae A.l-A.n are picked up with greater power by an on-board unit situated outside the area of

coverage C.l-C.n of the said communication antenna A.l-A.n and which is therefore replaced in response by the one correctly positioned in the area of coverage C.l-C.n. In the direction transverse to progress there are therefore provided in respect of the said two active areas of coverage two different working frequencies fl and f2 which are chosen one depending on the other and in such a way as to blind reception of the communication signals by on-board units 3 located in the areas of coverage C.l-C.n which are inactive in the given fraction of a period, without however disturbing correct communi¬ cations between the on-board units in the active areas of coverage.

Similarly, the jamming function operates in the direction of progress, the transmission frequency f3 at which the activation antennae AT operate being chosen in such a way as to blind reception by the on-board units 3 in the areas of coverage of activation AT of the signals transmitted by the communication antennae A.l-A.n, without however disturbing correct communication.

The discriminating effect of jamming is also obtained by providing suitable power for the signals radiated in the areas of coverage CT, C.l-C.n. Since the said areas of coverage are delimited in a drastic manner, it is sufficient for the transmission power in the active zone of each area of coverage CT, C.l-C.n to be of the same order of magnitude.

By way of non-limiting example, assuming the working band of the apparatus to be the 5.8 GHz band, the following frequencies will be advantageously provided: fl: 5797 MHz and f2: 5803 MHz, both with a transmission signal band of around 2 MHz, while f3 is fixed at

lb

5800 MHz.

The use of the antennae AT as jammers prevents the responses of tailing vehicles from being able to be attributed to different vehicles, appreciably reducing the possibilities of error of the apparatus.

As is obvious moreover from Figs. 16 and 17, the antennae A.1-A.8 are of the semi-parabolic type and comprise a radiating surface 50 which is located in a focal area of a semi-parabolic reflector 51. The latter is formed by a plate which in the direction of progress of the vehicles is fashioned in the shape of a semi- parabola. The semi-parabolic reflector 51 is fixed with its forward end to an articulation 52 which allows pivoting thereof about a transverse axis and is located with its concave part pointing towards the carriageway, and with the tangent to the said forward end oriented in a substantially horizontal direction, while the radiating surface 50 is oriented towards the reflecting surface and exhibits an angulation of 30* with respect to the plane perpendicular to the tangent at the forward end of the reflecting surface 51. The antenna AT, on the other hand, has a circular base and a diameter L10.

Illustrated in Fig. 11 is a more detailed example of a local station control unit 22. The latter has a central control processor 122, memories 222, read/write means 322 and 322 ' respectively for a removable storage medium and for a resident storage medium, various types of input/output interfaces 422, 422', 422", for example a parallel interface, a synchronous serial interface and an asynchronous serial interface to which may be con¬ nected various auxiliary devices of the station, these being indicated generically as 30, such as for example

signalling devices, automatically actuated barriers, etc. and via which the station control unit 22 communicates, by means of a multiplexer 24 and transmission means 2, with the central computer 15. An interface 522 is fur- thermore provided for a communication network, for example a network of the so-called Ethernet type, with which the local station control unit 22 communicates with the gate control units 21, 21'.

With reference to the method according to the invention, in order to guarantee extremely limited dimension in length LI and width L2 of the areas of coverage C.l, Cn, in conjunction with a relatively high maximum speed of travel, making it possible to obtain infinitesimal probabilities of error and complete execu- tion of the debit procedures, communication between the fixed transceiver station and the on-board units 3 is executed in two successive phases and in chronologically separated time intervals, in regard to the two gates PI, P2 respectively. The dimensions of the areas of c'overage are limited correspondingly with the time strictly necessary for transmission and reception, while the various internal procedures are dealt with in the time intervals immediately prior to the entry of the on-board units 3 into the areas of coverage C.l, Cn and in those intervals interposed between the two phases of communica¬ tion in relation to the two gates PI, P2. The following dimensionings emerged as suitable in an actuation design: with transaction times of around 300 ms, it is possible to ensure an error probability of the order of 10" ^β with a maximum speed, in the direction parallel to the major axis of the areas of coverage C.l-C.n, of around 120 km/h and with maximum transverse components of around 18 km/h.

while the areas of coverage C.l, Cn are LI - 1.5 m long and L2 = 0.5 m wide and the centres of the individual areas of coverage C.l-C.n are spaced apart by L3 - 0.375 m, in this case there being chosen a minimum spacing L12 of the areas of coverage C.l-C.n of the two gates PI, P2 of greater than 10 m, in particular for the proportions of 13.5 m stated below, which corresponds to a spacing L13 of the two gates of 15 m. The antennae A.l- A.n will in this case have a length L7 = 547.7 mm and a height L9 = 350 mm. The antennae are located at a height LI5 of around 6 m from the roadway. It is preferable to use an antenna AT of diameter L10 =■ 0.1185 m to obtain areas of coverage CT of the activation antennae AT which are large enough to ensure the internal initialization procedures of the on-board units 3 before entry into the areas of coverage C.l-C.n of the transceiver antennae A.l-A.n.

According to a further characteristic of the method, the antennae A.l-A.n are subdivided into two groups which are activated by the corresponding control facility 421, 421' in two semiperiods directly following one another. Each antenna group comprises respectively the antennae A.2n-1 and the antennae A.2n, which respec¬ tively form two transverse rows of areas of coverage C2n-1 and C2n, the areas of coverage C2n-1 of one of the two groups being intercalated with the areas of coverage C2n of the other group. Furthermore the method makes provision for, within the compass of each antenna group, the transmission frequencies fl and f2 to be distributed alternately to the said antennae C2n-1 and C2n, each antenna A.2n-1, which produces the area of coverage C2n-1 of a group associated with the frequency

fl, being brought directly alongside the antenna A.2n, which produces the area of coverage C2n associated with the same frequency fl. According to the design above, the antennae of each group A.2n-1 and A.2n are activated respectively for a time interval of 15 mβ. The method of operation of the antennae is evident in Figs. 5 and 12 to 15, in which the antennae C2n-1 and C2n of the respec¬ tively inactive group are illustrated dashed. Advan¬ tageously, the whole is dimensioned in such a way as to guarantee a repetition at least twice running of the transmission within the compass of each area of coverage C.l-C.n.

By virtue of the above, each area of coverage can comprise only one on-board unit. In this way an antenna A.l-A.n communicates with a single on-board unit at a time thereby making it possible to avoid both a protocol for transmission on several channels, with a consequent increase in costs, and also a column building up at the station on a single-carriageway lane. Furthermore, the apparatus according to the invention allows the vehicles to cross the areas of coverage with a certain transverse speed, operating correctly even in the event of over- takings and changes of carriageway. The enhancements to the method make it possible advantageously to limit appreciably the interference of transmission between the antennae associated with the adjacent areas of coverage further limiting transmission errors to extremely low levels.

According to a further enhancement, as emerges from Fig. 7, in addition to the radio communication system, the station is provided with a video device 37 for logging the presence and for identifying the position

with respect to a gate, in particular to the gate P2 of the travelling vehicles. As illustrated in Figs. 2 and 3, associated with the gate P2 of the fixed station is a plurality of telecameras 31 which are distributed equally spaced apart along an axis transverse to the roadway, at a height greater than the maximum height of the vehicles, and which point towards the said travelway. The optical axes O of the telecameras 31 are spaced apart to an extent L16 such as to ensure a resolution sufficient for logging a minimum distance of separation L17 between two vehicles one alongside the other. For a distance L16 equal to 0.75 m, a resolution L17 of 0.25 m is obtained.

With reference to Fig. 6, the telecameras 31 are connected at output to a video control unit 32 which can likewise be constructed from the modular and expandable type, similarly to what was described with regard to the gate control units 21 and the transceiver facilities 20 of the antennae A.l-A.n. The video control units 32 are connected to an image computer 33 which communicates via a LAN network 23 with the gate control units 21, 21' and with the local station control unit 22. In this case the use of telecameras 31 of the so-called linear scanning type is appropriate. The framing fields of the tele¬ cameras 31 are provided directly upstream of the areas of coverage C.l-C.n. By virtue of the construction of the above radiocommunication system and of the telecameras 31, it is possible to execute the logging of the presence of a vehicle in relation to the area of coverage C.l-C.n of the gate 2 and dual determination of its position, particularly in the direction transverse to the travel¬ way, once by means of the antenna A.l-A.n with which the corresponding on-board unit 3 of the vehicle is

98 PCI7EP96/01385

21 communicating and the other time by means of the telecameras 31. This may be used both to reduce any communication errors of the apparatus, and to log any users lacking the on-board unit 3 and attempting to speed through the station, or those users for whom, on account of particular conditions and of the infinitesimal but finite probability of error, the debit transaction has not taken place correctly. The invention in fact makes provision for the data relating to the two separate determinations of position to be compared in the station control unit 22. When a video log is not matched by a position log using transmission via the respectively active antenna A.l-A.n, the travelling vehicle is then crossing the station illegally. When the said data coincide, but the radio transaction has not been executed correctly, the error is logged. In this way it is there¬ fore possible subsequently to discriminate between users who cross the fixed station illegally and those for whom the automatic debit was not executed for reasons beyond their control.

An enhancement of the said optical system pro¬ vides as illustrated in Figs. 2 and 6 in relation but non-limitingly to the gate P2, a second row of telecameras 31' parallel to the first and a certain distance therefrom. This enables the speed of the vehicles to be logged in addition to their position. The two rows of telecameras 31, 31* also make it possible to be able to identify and hence classify the travelling vehicles by virtue of the reconstruction of their top plan form. This becomes possible with the aid of suitable software known per se, by virtue of which it is possible to recognize for example at least three groups of

698 PC17EP96/01385

22 vehicles, such as motor bikes, light vehicles and heavy vehicles.

According to a further characteristic, associated with the station is a device 38 (Fig. 7) for the video recording of vehicles illegally crossing the station and those for which the radio transaction was unsuccessful. With reference to Figs. 2 and 6, on the first gate PI a plurality of telecameras 35 is provided, oriented towards the second gate P2 and whose framing field 135 is pro- vided directly upstream of the areas of coverage C.l-C.n, in such a way as to photograph the rear part of the vehicles which bears the registration plate. It should be noted that the framing field 135 of the telecameras 35 contributes to the determination of the distance L13 between the two gates. The recording telecameras 35 are operated by a control and image recording unit indicated 36 in Fig. 6 which receives the data from the control unit 21' of the gate P2, from the station control unit 22 and from- the image computer 33 of the telecameras for logging the presence of vehicles and their position 31. In the two cases of violation and error described earlier, the control and image recording unit 36 stores the recorded images of the vehicle registration and transmits them, via the multiplexer 24 and the trans- mission means 2, to the central computer 15, while the continuously recorded images of the vehicles crossing the fixed station are erased.

With reference to Fig. 10, the gate control unit 21* for the gate P2 exhibits an interface 621 for com- munication with the said video recording device 38.

According to a further enhancement, instead of recording and analysing the video images manually, it is

possible to use an automatic system for interpreting the registrations of offending vehicles, whose image has been recorded or stored. For this purpose, it is possible to use a computer operating on the basis of interpretation software, for example of the so-called Optical Character

Recognition (OCR) type, which converts the captured image into a set of symbols which are recognizable according to the grammars of the countries of implementation and which is associated with a system for reading and processing the informational data thus extracted from the video image.

Some examples of the operation of the apparatus and of the method according to the invention under various conditions of maximum extreme criticality are illustrated diagrammatically in relation to a single gate in Figs. 12 to 14, wherein the alternately activated areas of coverage C2n-1 and C2n are indicated and the frequencies associated therewith, while d indicates the minimum transverse distances between the diverse on-board units in the various situations. Example 1

A single on-board unit is present at the point XI, in the central area of the area of coverage C.3 which in the first semiperiod of Fig. 12 is active. The argu- ments indicated below are valid for a certain limited region around the position XI. In the said semiperiod the transmission within the compass of the area of coverage C.3 is sufficiently protected from interferences from the transmissions at the frequency fl in the area of coverage Cl and C.5, the directly adjacent areas of coverage C2 and C.4 being inactive. In the subsequent semiperiod, illustrated in Fig. 13, in which the area of coverage C.3

698 24 PCI7EP96/01385

is inactive, the level of gain at the frequency fl of the area of coverage C. l and at the frequency f2 of the area of coverage C.4 at the point XI is insufficient to guarantee transmission between the station and the on- board unit. Therefore, the correct transaction takes place in the first semiperiod (Fig. 12) , in the area of coverage C.3, which in this case is used as vehicle position indication. Here there is no possibility of uncertainty due to a neighbouring vehicle, since the minimum distance loggable via video 37 of 0.25 m between the vehicles means that this response could come only from a vehicle occupying the area indicated in Figs. 12 and 13. Insofar as an additional vehicle might be nearby, the latter would have determined a communication of the said vehicle within the compass of the areas of coverage C2 and C.3, with the additional vehicle on the left or C.3 and C.4 with the additional vehicle on the right.

Example 2

In this- case the on-board unit is located at the point X2 of Figures 12, 13, in the area of overlap of two adjacent areas of coverage C.4, C.5 or in the vicinity thereof.

In the first semiperiod the transmission is sufficiently protected from a transmission at the fre- quency f2 in the area of coverage C.3 and C.7, allowing the on-board unit to communicate with the fixed station at the frequency fl in the area of coverage C.5. In the second semiperiod (Fig. 13), the transmission is suffi¬ ciently protected against a transmission at the frequency fl in the areas of coverage C.2 and C.6, allowing the on¬ board unit to communicate within the area of coverage C.4 at the frequency f2. If the transaction had taken place

only in one of the two βemiperiods, the on-board unit would have been logged in relation to the area of cover¬ age C.4 or C.5. This would entail ambiguities in the presence of an additional vehicle logged at the minimum distance of separation of 0.25 m. In fact, if the response took place in the area of coverage C.4 alone, it would also be possible for an additional vehicle to be situated in the area of coverage C.4, and so long as this vehicle had likewise not successfully executed the transaction (its position therefore being logged) , it would not be clear which of the two vehicles had executed the transaction. This is true similarly also for the area of coverage C.5. This uncertainty is eliminated by allowing the on-board units to communicate with more than one antennae A.l-A.n, since only the vehicle occupying the position X2 of the on-board unit can have com¬ municated within the compass of the area of coverage C.4 and C.5.

The above scenarios have demonstrated that the uncertainty in position is eliminated when the on-board units can communicate with all the antennae of the gate PI, P2, in relation to whose areas of coverage C.l-C.n they are situated. Therefore in the following examples this position logging uncertainty will not be considered further, until such time as multiple transaction is blocked. Example 3

With reference to Figs. 12 and 13, two on-board units are provided at the positions XI and X2 respect- ively, a mutual distance apart of d = 0.5 m.

Correspondingly with what was stated in the previous examples, in the first semiperiod the on-board

unit at XI will communicate at the frequency f2 in the area of coverage C.3 and that at position X2 will com¬ municate at the frequency fl in the area of coverage C.5. In the second semiperiod the on-board unit at XI will not communicate at all, while that at X2 will be able to communicate at the frequency f2 in the area of coverage C.4. Bxam lfl 4

In Figures 12 and 13, two on-board units are provided at the points X2 and X3, with d ■ 0.5 m.

In the first semiperiod the transmissions are generally insufficiently protected, the one with respect to the other within the compass of the area of coverage C.5 at the frequency fl, and so there will not be com- munication with either of the two on-board units. It may be possible to achieve communication with one of the two on-board units when the response signal from the two units is significantly different, and so the on-board unit at X2 or that at- X3 may possibly be able to communicate successfully in the area of coverage C.5. In the second semiperiod the on-board unit at X2 will communicate successfully in the area of coverage C.4 at the frequency f2, while that at X3 will communicate in the area of coverage C6 at the frequency fl. In the worst case, the communication will have taken place only in the second semiperiod. Since the vehicles associated with the on-board units should occupy the positions indicated, it is clear that here there is no ambiguity of correlation between vehicle and on-board unit.

Example 5

The on-board units have the positions X5 and X6

in Figs. 14 and 15, with d - 0.5 .

In the first semiperiod (Fig. 14) the on-board unit at X5 may or may not communicate at the frequency f2 in the area of coverage Cl, while the on-board unit at X6 communicates at the frequency fl in the area of coverage C.3. In the second semiperiod (Fig. 15), the on¬ board unit at X5 will communicate at the frequency f2 in the area of coverage C . l and that at X6 may or may not communicate at the frequency fl in the area of coverage C.4. Therefore the two on-board units at X5 and at X6 will be logged, the first in the areas of coverage C.l and C . l and the second in the area of coverage C.3. Example 6

The on-board units are located at X7 and X5' in Figs. 14 and 15, with d = 0.5 m.

In the first semiperiod, the response signals from the two on-board units are generally insufficiently protected from mutual interference, so there will be no communication at the frequency f2. Similarly -to what was indicated in Example 4, one of the two on-board units may possibly also communicate successfully in the area of coverage C.5. In the second semiperiod the unit at X7 will communicate at the frequency fl in the area of coverage C.4 and the unit at X5' will communicate at the frequency f2 in the area of coverage C.6, achieving a result akin to that of Example 4.

Examp e 7

Consideration will now be given to three on-board units located at XI, X2, X3, each at a distance d = 0.5 m from the adjacent one in Figs. 12 and 13.

In the first semiperiod the unit at XI will communicate at the frequency f2 in the area of coverage

C.3, while generally neither of the two units at X2 and ^' X3 will communicate at the frequency fl in the area of coverage C.5 or else just one of them will likewise succeed in communicating, as already described in Example 4. In the second semiperiod there will be no communication on the part of the unit at XI, while the unit at X2 will communicate in the area of coverage C.4 and that at X3 in the area of coverage C.6, achieving unambiguous identification of the vehicles to which the on-board units at XI, X2, X3 belong. Example 8

The on-board units are located at X5, X6 and X7 in Figs. 14 and 15, at a distance d = 0.5 m apart.

In the first semiperiod the unit at X5 may possibly communicate or not communicate at the frequency f2 in the area of coverage C.l. The unit at X6 will communicate at the frequency fl in the area of coverage C.3 and that at X7 will communicate at the frequency f2 in the area of coverage C.5. In the second semiperiod the unit at X5 will communicate at the frequency f2 in the area of coverage C.2, while in respect of the units at X6 and X7 the communication may or may not take place according to what has already been described earlier in Example 6. Therefore, the unit at X5 will be pinpointed in the area of coverage C.2, possibly on the left thereof if a communication also took place in the area of coverage C.l. In the worst case, moreover, the unit at X6 will be pinpointed in the area of coverage C.3 and that at X7 in the area of coverage C.5. In this case also no uncer¬ tainties will remain regarding the correlation between a vehicle and the on-board unit.

698 ₂ 9 PCI7EP96/01385

Example 9

The on-board units are located at X6, X7 and X5* in Figs. 14 and 15. In the first semiperiod the unit at X6 will communicate at the frequency fl in the area of coverage C.2, while the communication in respect of the on-board units at X7 and at X5' in C.3 at the frequency f2 is not possible for either of the two or perhaps for just one of the two as described in Example 6. In the second semi¬ period the unit at X5 ^■ will communicate at the frequency f2 in the area of coverage C.6, while, similarly to what was stated in the previous examples, neither of the two units at X6 and X7 will be able to communicate in the area of coverage C.5 at the frequency fl, or else just one of them may be able to communicate successfully when the response signals from the units exhibit a sufficiently different level.

In the worst case, the unit at X6 will then communicate in the area of coverage C.3, the unit at X5' in the area of coverage C.6, while the unit at X7 will have been unable to communicate in any way.

With the help of the position logging and identi¬ fication video system 37, the vehicle associated with the on-board unit at X7 will be logged and identified in relation to the gate P2. Still, using chronological records in the data of the transactions of the units at X6 and X5' it is possible that the vehicle associated with the unit at X7 will be granted the benefit of the doubt and the missing transaction will not be regarded as a violation, but rather a communication error.

In this case it is necessary to underline that

98 _3Q PCIYEP96/01385

this scenario is extremely rare since in practice it requires the chronological coincidence of the transit of three mutually aligned on-board units at a distance 0.5 m apart. It is furthermore possible to avoid such a problem from arising by reducing the lateral dimensions of the areas of coverage C.l-C.n. On the other hand this involves a greater number of antennae A.l-A.n, so that, taking into account the extremely low probability with which the aforesaid situation may be repeated in practice, this expedient is not fully justified. Example 10

Example 10 refers to Figs. 12 and 13, in which more than four vehicles are simultaneously crossing the areas of coverage C.l-ClO, the corresponding on-board units being located at the points XI to X3 and XI', X2' , X3• , X3", each of them a distance of 0.5 m apart.

This situation can be reduced to the previous examples since it can be broken down into the following subgroups: three on-board units in position XI, X2, X3, two units in position XI ¹ , X2*, two units in position X2' , X3 ^■ ; one unit in position 1 and one unit in position X2, the positions XI', X2' , X3 ^■ and X3" being similar to the positions XI, X2, X3, but corresponding with differ- ent areas of coverage. Example 11

Similarly to Example 10 the situation of more than four on-board units located at the positions X5, X6, X7, X5' , X6* , X7• and X5" can be broken down into the scenarios already discussed in the previous examples: three units in position X5, X6, X7; two units in position X8, X6■ ; two units in position X7' , X5 ¹ ; one unit in

PCI7EP96/01385

31 position X5 and one unit in position X7, the consider _¬ ations of Example 10 holding.