WO1990015401A1

WO1990015401A1 - Apparatus for charging vehicles

Info

Publication number: WO1990015401A1
Application number: PCT/GB1990/000887
Authority: WO
Inventors: Geoffrey Stringer Race Hunter; Brian Oldridge
Original assignee: Geoffrey Stringer Race Hunter; Brian Oldridge
Priority date: 1989-06-10
Filing date: 1990-06-07
Publication date: 1990-12-13
Also published as: GB8913399D0; EP0475990A1; EP0475990B1; DE69017905T2; DE69017905D1; AU5721390A

Abstract

Apparatus for charging travel of a vehicle in congested traffic situations comprises a receiver (1) for accommodating a medium (2), carrying data related to prepaid units, first monitoring means for monitoring distance travelled by the vehicle, second monitoring means for monitoring at least one further variable, calculating means responsive to the first and second monitoring means for generating a charge signal indicative of a chargeable unit should the relationship between distance travelled and the further variable indicate a given level of congestion, and means operative in response to a charge signal to decrease the number of prepaid units carried by the medium.

Description

APPARATUS FOR CHARGING VEHICLES

This invention relates to apparatus for charging vehicles in congested traffic situations.

The difficulties that result from traffic congestion are well known, and require no elaboration here. Schemes have been proposed in the past for inhibiting drivers from entering potentially congested areas, and for charging those who do enter such areas. For example, the so-called cordon pricing scheme seeks to levy a charge on every vehicle entering a specified area during a specified time period. This requires the installation of apparatus adjacent to or in the highway at the points of entrance, together with the establishment of complex billing organisations for ensuring that charges are rendered and met. These difficul ies, together with perception by drivers that such system is unfair and infringes civil liberties have militated against its adoption. However, it is recognised that if an effective charging system can be established then it would act as a deterrent against entering a congestion situation.

According to the present invention apparatus for charging travel of a vehicle in congested traffic situations comprises a receiver for accommodating a medium carrying data related to prepaid units, first monitoring means for monitoring distance travelled by the vehicle, second monitoring means for monitoring at least one further variable, calculating means responsive to the first and second monitoring means for generating a charge signal indicative of a chargeable unit should the relationship between distance travelled and the further variable indicate a given level of congestion, and means operative in response to a charge signal to decrease the number of prepaid units carried by the medium.

It will be seen that such a system can be implemented relatively easily, without any necessity for new apparatus or infrastructure adjacent to or in the highway, although, as explained hereinafter, the system can advantageously be such as to interact with equipment provided outside the vehicle. The medium carrying the prepaid units can be in such a form that it may readily be bought or replenished from automatic machines or over the counter at garages, service stations or any other suitable outlet. The prepaid units carried by the medium are automatically decreased whenever the vehicle is in a situation determined by the calculating means as a congestion situation. Thus, the apparatus of the invention is based on a concept that does not charge for the use of roads as such, but only charges vehicles that are at a time and place where they are contributing towards a defined level of congestion.

The invention requires that each vehicle be fitted with a suitable receiver for the prepaid medium. Receivers may be fitted as standard in new vehicles, and may be retrofitted to existing vehicles. They are capable of being manufactured cheaply, and their cost will not impose a great burden on the vehicle owner. It is also envisaged that the receiver and the calculating means may form part of an in- vehicle computer capable of performing many other functions.

In one embodiment of the invention the second monitoring means comprises means for monitoring elapsed time, and the calculating means is operative to generate a charge signal should the time taken to travel a given distance be greater than a predetermined figure. The calculating means can thus be considered as calculating average speed over a given distance, and determines a congestion situation, so generating a charge signal, should that average speed be less than a given value.

In another embodiment the second monitoring means comprises means for monitoring the number of stops made by the vehicle, and the calculating means is operative to generate a charge signal should the number of stops in a given distance be greater than a predetermined figure. The calculating means thus determines congestion as being more than a predetermined number of stops in a given distance.

Preferably the calculating means is capable of responding both to average speed and to the number of stops in a given distance, to generate a charge signal should either of these calculations indicate a congestion situation.

The calculating means can be realised in many different ways, for example using large scale integrated techniques, but desirably it forms part of a microprocessor that may form part of an in-vehicle computer. In one preferred form the calculating means comprises a first store having an initial value and a reset value, the difference between the two values being equivalent to a given number of distance units, and a second store having an initial value; the first monitoring means is operative to vary the value of the first store towards the reset value; the second monitoring means is operative to vary the value of the second store towards a charge value; and the calculating means is operative to generate a charge signal should the second store reach the charge value before the first store reaches the reset value.- Preferably the apparatus includes means for resetting both the first and second stores to their initial values when the first store reaches the reset value. It will thus be seen that the only way in which the generation of a charge signal can be avoided is by actual travel of the vehicles in a non-conges ion situation in order to achieve resetting of the store. Thus, any attempt to interfere with the system by bypassing the distance sensor and first monitoring means would be self-defea ing. If, within a first given distance interval, a charge signal has not been generated then a new distance interval is started, and the vehicle is deemed to have been in a non- congestion situation over the first distance interval. If a charge is recorded within a first given distance interval, then that charge applies to the whole of that interval, and a new charge signal cannot be generated until the first distance interval has been completed.

This is considered to be the most acceptable way of operating, although in alternative systems it will be appreciated that it would be possible to reset both the first and second stores to their initial values whenever a charge signal is generated.

The apparatus will operate effectively with only a single level of charging. However, it may be desirable to have two levels of charging, the first level being imposed in a first level of congestion, and the second level being imposed in a higher level of congestion.

In a preferred form of operating a two level charging system, the apparatus includes means storing first and second charge values; the calculating means is operative to generate a first charge signal if the second store reaches the first charge value before the first store reaches the reset value; means are provided for storing the first charge signal; the calculating means is operative to generate a second charge signal if the second store reaches the second charge value before the first store reaches the reset value; and the first charge signal is inhibited if a second charge signal is generated.

In such arrangement the second charge signal will obviously be effective to decrease the prepaid medium to a greater extent than the first charge signal. If desired, more than two levels of charging could equally well be used.

The prepaid medium may take any one of a number of different forms, capable of being read and decremented mechanically, electrically, electronically, magnetically, optically, or by other means. Preferably, however, it is in the form of a card incorporating a data memory carrying the data relating to prepaid units, the receiver is a card¬ holder, and interface means are provided between the card and the card-holder to enable charge signals fed to the card-holder to decrease the number of prepaid units in the data memory, The card may also incorporate a programme memory, and may further incorporate a data processor for controlling the monitoring and calculating means, in which case interface means are provided between the card and the card-holder to enable distance-related data to be transmitted from a sensor on the vehicle to the data processor. In the latter case the card is desirably of the type that is commonly known as a "smart card". A smart card is similar in size and appearance to a conventional plastics credit card, but contains an in-built microprocessor, memory, data storage facility and back-up battery.

The interface means between the card and the card¬ holder is desirably inductive coupling means, or the interface may incorporate terminal pads on the card and card-holder.

Preferably means are provided for disabling the vehicle if no prepaid data medium is present in the receiver. Thus, a vehicle cannot be started unless the prepaid data medium has actually been obtained and inserted into the receiver, and the potential charge effected by the apparatus of the invention can thus not be avoided if the vehicle is to be rendered mobile.

Desirably, disabling means are provided for disabling the vehicle, the disabling means being placed in an operable condition after the data carried by the medium indicates zero prepaid units. It would almost certainly be impractical to operate the disabling means immediately the prepaid units carried by the medium are reduced to zero, and regardless of the surrounding traffic conditions. Accordingly, it is preferred that the disabling means only operates after the vehicle engine has been switched off. Thus, restarting the engine is prevented. The disabling means may be the same as the means used for disabling the vehicle if no prepaid medium is present in the receiver.

The apparatus preferably includes means for storing charge signals after the disabling means has been placed in an operable condition, and means for decreasing the prepaid units on insertion of a new prepaid data medium into the carrier by a value in accordance with the stored charge signals. This ensures that any charge signals that have accumulated after the disabling means is placed in an operable condition cause a decrease of the new prepaid medium, so that charging is not avoided.

The disabling means may take any one of a number of different forms. It may operate on the electrical system of the vehicle, or on the fuel system of the vehicle. It is envisaged that the most effective arrangement will be for the disabling means to be a valve normally closing a fuel outlet from a fuel tank of the vehicle, and a valve actuator requiring a continuous supply of electrical power to hold the valve open, the power supply being enabled by the presence in the carrier^"of a medium carrying prepaid units.

This arrangement can also form part of a vehicle anti- theft system, if the valve actuator can only be enabled after receipt oϊ a correct ..authorisation code. Code generating means can be incorporated in the vehicle, for example in the form of an alphanumeric keypad. The correct code must then be keyed into the pad by the driver in order to enable the valve actuator.

It is further envisaged that such alphanumeric keypad may be carried by or incorporated into the prepaid medium. If, for example, that medium is a smart card then on purchase of the card the purchaser may enter onto the card his own authorisation code. Insertion of the card into the card-holder then causes that code to be read, and transmission of the correct code, together with presence of the card causes enablement of the valve actuator and the opening of the valve, so allowing fuel supply. Indeed, this concept may be extended, and such a programmed card may be used, with appropriate sensors, in place of conventional locks and keys for the i-gnition system and for the vehicle door, boot and bonnet locks. In order that the invention may be better understood, specific embodiments thereof will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:-

Figure 1 is block diagram of the apparatus;

Figure 2 is a schematic operating diagram of ^' parts of the apparatus; and

Figure 3 is a diagrammatic representation of a decoder and a valve forming part of the apparatus.

Referring to figure 1 a vehicle having apparatus according to the invention is fitted with a card-holder 1 for accommodating a smart card 2. The card-holder is secured in the vehicle in a convenient location for the driver, and may incorporate its own power supply 3 or, more preferably, be connected to the power supply 4 of the vehicle. The power supply is connected to an oscillator/modulator unit 5, a transmitter/amplifier unit 6, a receiver 7 and a demodulator 8. The transmitter/amplifier 6 and the receiver 7 are each connected to respective inductive loops 9 and 10. The oscillator/modulator and the demodulator are connected through a serial interface 11 to a distance sensor impulses sealer 12 and, optionally, to a fund register 13, to a decoder and valve assembly 14 and to other vehicle immobilisation devices 15. The fund register may include a visual display 13a, for example a liquid crystal display.

The distance sensor impulses sealer 12 is in the form of a suitable electronic sensor capable of creating output pulses in accordance with the distance travelled by the vehicle. In many modern vehicles a unit of this type is already present. However, for vehicles where that is not the case then a suitable sensor unit may simply be inserted at one end of the speedometer cable either adjacent to the gearbox or transmission unit or adjacent to the speedometer/odometer. It is anticipated that the most convenient arrangement will be for the sealer to supply an electronic output pulse each time a given distance, for example one meter, is travelled by the vehicle.

The smart card 2 incorporates a microprocessor 16, programme memory 17, data memory 18, internal clock pulse generator 19, alphanumeric keypad 20 and communications and power interface 21. The interface is connected to an induction loop 22 which, when the smart card is properly located in the receiver, cooperates with the loops 9 and 10 so that the interface receives power and data from the transmitter/ amplifier 6, and transmits data to the receiver 7. The smart card also incorporates an in-built battery, for maintaining power to at least the memory devices 17 and 18.

The programme memory 17 of the smart card will contain the operating systems and application programmes for the apparatus. It may also contain charging criteria and other criteria such as reset values, if required. The memory may be read only, or it may be programmable.

The data memory 18 of the smart card will contain information related to the number of prepaid units remaining, together with data (either predetermined or calculated) showing any one or more of the following:- the assessment distance (i.e. the distance interval over which congestion is monitored) , the minimum average velocity required over the assessment distance to avoid charging, the number of stops within the assessment distance that are permitted before charging is initiated, the value at which the charge signals are to be set to decrease the value of the funds and the code sequence which must be keyed into the alphanumeric keypad 20 in order to activate the apparatus.

The programmes control the data processor to operate in a manner analogous with that illustrated by the operating diagram of figure 2. It will be appreciated that the actual software may be written in many different ways to give the required effect. Indeed, the operating diagram may be implemented by techniques other than microprocessor techniques. It will equally well be appreciated that the required outputs may be obtained in ways other than that indicated by the figure 2 operating diagram, and again that writing suitable software is within the competency of those skilled in the art.

Referring to figure 2 _cthe scaled distance pulses received by the card interface 22 from the card-holder 1 are fed to a zero detector 30, to a stop/distance up/down counter 31 and to a time/distance up/down counter 32. The zero detector 30 may respond only to an absolute stop and then operates to give an output signal on line 33.

Alternatively the detector may receive clock pulses from generator 19 and give an output signal on line 33 if no distance pulse is sensed in a given time. The zero detector can then be set to any required time period, so that it may, for example respond to a very low crawl speed in order to prevent charge avoidance by skilful crawl driving. In either case a signal on line 33 will increase the stop count value in the counter 31. The distance section of the counter 31 has an initial value that is desirably equal -to the number of pulses received during travel over the assessment distance, for example 0.5 kilometers. that value being decreased towards zero as distance pulses are received. If, during travel over the given assessment distance, i.e. at any time before the distance value section of counter 31 is reduced to zero, the stop count value recorded in the counter 31 exceeds the value set in a first comparator 34 then this comparator is set to provide a first level charge output signal on line

34a. If the stop count value then continues to increase, and, before the distance value section of counter 31 is reduced to zero, exceeds the level set in a second comparator 35 then that comparator is set to give a second level charge output signal on line 35a, and to override or inhibit the first level charge signal that would be provided from the comparator 34. The first or second level charge signal as appropriate is accumulated in a store 36.

Vhile travelling over the same assessment distance the counter 32 is also operating in response to distance pulses to decrease a distance section of the counter similar to that in the counter 31. Simultaneously a time counter fed from the clock pulse generator 19 is increasing. If during travel over the assessment distance a first preset allowed time as stored in a comparator 37 is exceeded then that comparator stores a first level charge signal on line 37a. If, thereafter, a second, higher allowed time set in a second comparator 38 is also exceeded then that comparator is set to provide a second level charge output signal on line 38a, and the first level signal from comparator 37 is overridden or inhibited. The charge signal at the appropriate level is stored in store 36. This may be designed to add together the charge signals received from both counters 31, 32, but will preferably operate to charge the higher value received from the comparators associated with counters 31 and 32, or to charge the value resulting from only one of the counters if those values are equal.

Whatever method is used, completion of each assessment distance (i.e. when the distance counters of units 31 and 32 reach zero) initiates a charge implement signal on line 39. causing store 36 to decrease appropriately the value of the units stored in the data memory 18 and to provide a signal through the interface with card-holder 1 to the funds register 13, the display of which will change accordingly. The charge implement signal also resets the store 36, resets the distance counters in units 31 and 32 to the assessment distance, and simultaneously resets to zero the stop count value in unit 31 and the time counter of unit 32.

Charging as necessary continues in this manner, the stored prepaid units being decreased in accordance with the charge signals. For example, first level charging may be implemented if, over a half kilometer distance, the vehicle stops six times or the time taken exceeds four minutes; and second level charging may be implemented if, over a half kilometer distance, the vehicle stops ten times or the time taken exceeds six minutes. These criteria may be set as desired.

If the prepaid units in the data memory on the card are reduced to zero while the vehicle is running, then this fact is registered and thereafter the store 36 simply holds the following charge signals and is not reset after coverage of each assessment distance. Once the vehicle has stopped and the engine has been switched off it will be necessary, as hereinafter explained, to remove the zero value card and insert a card carrying valid prepaid units. On insertion, the store 36 is automatically interrogated, and any stored charge units cause a corresponding decrease in the value of the prepaid units on the newly inserted card.

The recording and charging system described may come into effect immediately the engine of the vehicle is started. However, the programme may allow a free period before the counts commence, may allow for zeroing of the charge pulse store if the engine is switched off after a short time interval (e.g. four minutes); or may allow such zeroing only after elapse of a further time interval during which the engine has not been restarted.

It is envisaged that when the system is operated by a smart card then that card will be capable of use over a long period, and that the data memory 18 of the card can be loaded with further prepaid units by insertion of the card into an appropriate terminal, following payment of the required amount. That terminal can act not only to load further units onto a card, but it could also operate to change the operating parameters already stored on the card, for example to change the assessment distance, to change the first and second level charging criteria and to change the charge rates for those levels.

As thus far described the invention operates in a self- contained manner within the vehicle and is independent of any equipment that may be provided outside the vehicle. It may be advantageous, however, for the device of the invention to be able to communicate with receivers and transmitters that are external of the vehicle. Thus, the vehicle may incorporate a system for receiving, processing and reacting to information transmitted from external sources, and also to have the capability of transmitting data from the vehicle to external sources. Such communication could be by a two-way high-capacity data- communications link of any form between vehicle equipment and roadside beacons or other appropriate devices using as the transmission medium, for example, radio waves, infrared laser or, more preferably, microwave.

It will be appreciated that congestion charging may only be necessary in urban areas or on very heavily used or other selected highways, and that such charging may not be appropriate in rural areas. Thus, the charging system of the invention could be activated by receipt of an appropriate signal when the vehicle enters a potentially congested or pre-selected area, and may be deactivated when the vehicle leaves such area. It may also happen that a motorist encounters congestion through no fault of his own, for example by being caught in traffic backed up from a motorway accident. In such circumstances, transmission means on the relevant section of the motorway could be operated to transmit a signal so that the congestion charging system is deactivated, a further signal being operated to re-activate it back on when traffic is again flowing normally.

Transmission of signals from outside the vehicle can be used to change or augment data held in the charging system of the invention, for example to change the pricing structure in accordance with pre-determined levels of congestion on selected roads, city cordons or within any defined region. Such a data communications link could also provide for automatic debiting of the prepaid units carried by the medium in order to effect collection of tolls for bridges or tunnels, or simply tolls for road usage. In a similar manner, the prepaid units may be debited to charge for on street or off street car parking, so eliminating parking meters etc. Fines for illegal parking could also be automatically debited by generation of a signal directed to a vehicle concerned, and fines for other traffic infringements could similarly be imposed.

A data communications link could also have other uses, for example providing information on traffic flows and congestion levels for statistical or other purposes, for classification of vehicles passing a particular point (for example by their licencing class) , for providing an information service to drivers, for checking that the vehicle charging system is fully operative, and for providing a warning if that device has been tampered with.

Although the charging system of the invention has been described as a stand-alone unit it may form part of an integrated in-vehicle computer capable of performing many other functions.

The congestion charging apparatus as described may be linked to and form part of, an anti-theft system for the vehicle. This system comprises the decoder and valve 14 shown in figures 1 and 2. and described in more detail with reference to figure 3. It may also include other immobilisation devices operable on the vehicle electrical or locking systems, and possibly linked to an alarm device.

Referring to figure 3 this shows part of a fuel tank 41 of the vehicle, fuel being taken from the tank by a fuel supply pipe 42. Entry to the pipe 42 is preferably through a conical valve seat 43 in which is located a ball valve 44 carried at the lower end of a stem 45 constrained by guides (not shown) for substantially vertical movement within the tank. The upper end of the stem is received within a solenoid 46, forming part of a valve actuator, which also comprises an energiser 47 for the solenoid and code recognition means in the form of a decoder 48. The valve is biased to its normally closed position by gravity, and the solenoid, when energised, holds the valve open against that force. The decoder is preferably encapsulated in a sealed housing, for example an epoxy or acrylic resin encapsulation, which is secured to the top of the fuel tank by a suitable, substantially indestructible adhesive. Any attempt to gain access to the decoder would thus inevitably result in destruction thereof and severe damage to the fuel tank. The electrical circuits of the decoder and energiser are connected by a twin line 49 to the serial interface 11 of the card-holder 1. The energiser and decoder are linked so that the energiser can only operate once a correct authorisation code has been received by the decoder, and that code is generated^' by proper insertion of the smart card (with prepaid units thereon) into the card-holder 1, and either correct operation of the alphanumeric keypad 20 of the smart card or correct reading of a code already held in the data memory of the smart card.

Thus, in order to start the vehicle the correct number must be keyed into the smart card and the microprocessor therein stores the data sequence constructed by the keying operation. If required, the input code may be compared with a code already stored in the data memory of the card, although this is not necessary. Proper insertion of the card causes the stored data sequence to be transmitted through the serial interface 11 of the card-holder 1 to be passed as a digital signal on line 49 to the decoder 48. It is there duly recognised, if correct, and the interface then applies power to the energiser 48. The valve is thus opened and held open by the solenoid and the engine can be started and operated normally, the ignition already having been enabled either by the conventional ignition switch or by insertion of the smart card. If the authorisation code that has been entered is incorrect, or if no smart card is present, the energiser cannot receive a source of power and the valve cannot be opened. Thus the vehicle is immobi1ised.

The decoder circuit is preferably such that having been successfully operated it will generate a related return data stream to the data processor, which will reset the apparatus for a future operation. If desired, immediately following the code entry operation the entered code may be displayed on the display of the fund register 13 to check on the keyed code. That display should continue for only a short time after entry, and the display unit will then revert to an indication of the number of prepaid units that are still carried by the smart card.

The decoder may be programmable in order to store any one of a number of possible authorisation codes, and that programming may be effected from the keypad. Obviously, reprogramming must not occur until after the decoder has received a correct, already stored authorisation code, but suitable operation of keys on the keypad can readily control this operation. The decoder must obviously be able to hold a stored code without requiring continuous power supply to effect such storage.

It will be understood that there are. many variations possible from the apparatus that has been particularly described. For example, the keypad for the authorisation code need not be incorporated into the smart card, but can form part of, or be carried by the card-holder, or indeed may be located in any other convenient part of the vehicle. When in a location other than on the smart card, the keypad may be replaced by any other suitable code generating means, for example an image processing system for giving recognition of a thumbprint, fingerprint or of a coded card or other element. Indeed, the use of an authorisation code is not essential to the congestion charging concept of the invention, annd input code authorisation could be omitted completely. A hardwired electrical connection system between the card-holder 1 and the decoder is preferred, although in other embodiments, part of the system could be replaced by fibre optics system for data transfer between the code generating means and the decoder. The fuel valve may be located on the outside of the fuel tank or elsewhere in the supply line, or some other form of immobilisation may be used. The fuel valve, fuel outlet from the tank, energiser and decoder could be incorporated into a single, pre-formed encapsulation which may simply be inserted through a suitable hole , cut into the tank, and bonded to the tank wall.

The fund register display has been shown as incorporated as part of the card-holder or as having permanent location elsewhere in the vehicle. However, it is possible to incorporate a liquid crystal display onto a smart card as an alternative.

Other modifications will be readily apparent.

Claims

1. Apparatus for charging travel of a vehicle in congested traffic situations, comprising a receiver for accommodating a medium carrying data related to prepaid units, first monitoring means for monitoring distance travelled by the vehicle, second monitoring means for monitoring at least one further variable, calculating means responsive to the first and second monitoring means for generating a charge signal indicative of a chargeable unit should the relationship between distance travelled and the further variable indicate a given level of congestion, and means operative in response to a charge signal to decrease the number of prepaid units carried by the medium.

2. Apparatus according to claim 1 in which the second monitoring means comprises means for monitoring elapsed time, and the calculating means is operative to generate a charge signal should the time taken to travel a given distance be greater than a predetermined figure.

3. Apparatus according to claim 1 or claim 2 in which the second monitoring means comprises means for monitoring the number of stops made by the vehicle, and the calculating means is operative to generate a charge signal should the number of stops in a given distance be greater than a predetermined figure.

4. Apparatus according to any one of the preceding claims in which the calculating means comprises a first store having an initial value and a reset value, the difference between the two values being equivalent to a given number of distance units, and a second store having an initial value; the first monitoring means is operative to vary the value of the first store towards the reset value; the second monitoring means is operative to vary the value of the second store towards a charge value; and the calculating means is operative to generate a charge signal should the second store reach the charge value before the first store reaches the reset value.

5. Apparatus according to claim 4 including means for resetting both the first and second stores to their respective initial values when the first store reaches the reset value.

6. Apparatus according to claim 4 or claim 5 and including means storing first and second charge values; the calculating means is operative to generate a first charge signal if the second store reaches the first charge value before the first store reaches the reset value; means are provided for storing the first charge signal; the calculating means is operative ..to generate a second charge signal if the second store reaches the second charge value before the first store reaches the reset value; and the first charge signal is inhibited if a second charge signal is generated.

7. Apparatus according to any one of the preceding claims in which the medium is in the form of a card incorporating a data memory carrying the data relating to prepaid units, the receiver is a card-holder, and interface means are provided between the card and the card-holder to enable charge signals fed to the card-holder to decrease the number of prepaid units in the data memory.

8. Apparatus according to claim 7 in which the card incorporates a programme memory.

9. Apparatus according to claim 8 in which the card incorporates a data processor for controlling the monitoring and calculating means, and interface means are provided between the card and the card-holder to enable distance- related data to be transmitted from a sensor on the vehicle to the data processor.

10. Apparatus according to any one of claims 7 to 9 in which the interface means between the card and the card¬ holder comprises inductive coupling means.

11. Apparatus according to any one of claims 7 to 9 and including a receiver for receiving signals transmitted from externally of the vehicle,and means responsive to the signals for changing the data memory and/or the programme memory of the card.

12. Apparatus according to any one of the preceding claims in which means are provided for disabling the vehicle if no prepaid data medium is present in the receiver.

13. Apparatus according to any one of the preceding claims in which disabling means are provided for disabling the vehicle, the disabling means being placed in an operable condition after the data carried by the medium indicates zero prepaid units.

14. Apparatus according to claim 13 in which the disabling means only operates after the vehicle engine has been switched off.

15. Apparatus according to claim 13 or claim 14 and including means for storing charge signals after the disabling means has been placed in an operable condition, and means for decreasing the prepaid units on insertion of a new prepaid data medium into the carrier by a value in accordance with the stored charge signals.

16. Apparatus according to any one of claims 13 to 15 in which the disabling means comprises a valve normally closing the fuel outlet from a fuel tank of the vehicle, and a valve actuator requiring a continuous supply of electrical power to hold the valve open, the power supply being enabled by the presence in the carrier of a medium carrying prepaid units.

17. Apparatus according to claim 16 and including a code recognition means, the valve actuator only being enabled after receipt of a correct authorisation code by the code recognition means, the code recognition means and valve actuator being incorporated in a sealed unit secured to the fuel tank of the vehicle.

18. Apparatus according to claim 17 and including code generating means in the form of an alphanumeric keypad, means for storing a data sequence constructed by a plurality of sequential keying oeprations, and means for transferring the data sequence as serial data to the code recognition means.

19. Apparatus according to claim 18 in which the alphanumeric keypad is carried by or incorporated into the medium.