WO2007056804A1 - Improved transport system - Google Patents

Abstract

An electric power supply system for providing power to electrically powered road vehicles travelling over a road surface comprises a plurality of pairs of electrically conductive members (10)positioned on a road surface (16), each of the pairs of electrically conductive members (10) being electrically insulated from the other pairs of electrically conductive members. When a vehicle(50) travelling along the road travels over one pair of electrically conductive members (10) a source of direct current electricity provides a DC voltage to the pairs of electrically conductive members. The system also includes switching means operative to supply DC power to a pair of electrically conductive members (10) when a vehicle (50) is travelling over that pair, the switching means being operative to turn off the supply of DC power to a pair of electrically conductive members when no vehicles are travelling over that pair of electrically conductive members.

Description

IMPROVED TRANSPORT SYSTEM

FIELD OF THE INVENTION

The present invention relates to an improved transport system. More particularly, the present invention relates to an improved transport system that is suitable for use by electrically powered vehicles.

BACKGROUND TO THE INVENTION

In my Australian Patent No. 712902, 1 describe a system for the universal use of electric powered road vehicles. In my earlier patent, I described a system in which a succession of 20 metre long copper strips was fixed to the road surface. Each of the 20 metre long copper strips were positioned end to end along each lane of the road and were electrically isolated from each other. Alternating current electric power was provided to each section. When an appropriate electrically powered vehicle travelled over each section of copper strip, a UHF transmitter mounted to the vehicle turned on the power supply to this section of copper strip that the vehicle was travelling over. Electric pick-up arms on the vehicle contacted the copper strips and obtained electricity from the copper strips. This electricity from the copper strips was then used to run an electric motor on board the vehicle (and also to run vehicle accessories and, optionally, to recharge batteries on the vehicle). The electricity supply to each copper strip was only turned for 1.5 seconds, i.e. for the time during which the vehicle was passing over that section of copper strip. In the absence of a signal from a vehicle, the power to that section of copper strip remained off. This improved the safety of the system.

My earlier Australian Patent No. 712902 also describes a number of other features of the system. The entire contents of my earlier Australian Patent No. 712902 are herein incorporated by cross-reference. The applicant does not concede that any of the prior art disclosed in the specification forms part of the common general knowledge in Australia or elsewhere. Throughout this specification, the term "comprising" or its grammatical equivalence shall be taken to have an inclusive meaning unless its context clearly indicates otherwise.

BRIEF DESCRIPTION OF THE INVENTION In a first aspect, the present invention provides an electric power supply system for providing power to electrically powered road vehicles travelling over a road surface comprising a plurality of pairs of electrically conductive members positioned on a road surface, each of the pairs of electrically conductive members being electrically insulated from the other pairs of electrically conductive members and wherein a vehicle travelling along a road travels over one pair of electrically conductive members and then travels over a next pair of electrically conductive members and so forth, a source of direct current electricity to provide a DC voltage to the pairs of electrically conductive members, and switching means operative to supply DC power to a pair of electrically conductive members when a vehicle is travelling over that pair, the switching means being operative to turn off the supply of DC power to a pair of electrically conductive members when no vehicles are travelling over that pair of electrically conductive members.

Preferably, the DC voltage difference between each conductor in a pair of conductors does not exceed 600 volts. More preferably, the DC voltage difference between each conductor in a pair of conductors does not exceed about 450 volts.

Suitably, each conductor is at a voltage relevant to earth that does not exceed plus or minus 250 volts, more preferably not exceeding plus or minus 225 volts.

The electrically conductive members are suitably arranged such that a vehicle travelling over the electrically conductive members picks up electrical power from the conductive members by contact elements on the vehicle coming into contact with the electrically conductive members.

The electrically conductive members may comprise strips of electrically conductive material. Copper conductor strips are most suitable. Other electrically conductive materials may also be used. In one embodiment, the electrically conductive strips are generally parallel to each other. Advantageously, the electrically conductive members will also have good 'sliding contact' conduction properties so that a vehicle travelling over the members can efficiently pick up electrical energy therefrom. Advantageously, the members will exhibit good corrosion resistance. In one embodiment, the electrically conductive strips are generally parallel to each other.

The electrically conductive strips may be positioned on the road such that they are insulated from each other and from earth (the road surface). Suitably, the electrically conductive members are laid on an adhesive insulating base which insulates them from each other. The electrically conductive strips may be bonded to the road surface by an epoxy adhesive. Alternatively, the electrically conductive strips may be bonded to tiles that are then placed in or on the road surface.

The power supply system in accordance with the present invention comprises a series of separate, electrically isolated electrically conductive strips. Each pair of strips represents a power supply section. Each pair of strips may be provided with a dedicated source of direct current power. Alternatively, a source of direct current power may provide direct current electricity to two or more pairs of strips.

Each pair of strips may have a length of from, say 50 metres to 500 metres, more suitably from 100 metres to 500 metres. The actual length of each pair of strips will depend upon the cross-sectional area of each strip and the voltage applied to each pair of strips. As voltage is reduced, the thickness of electrically conductive strips and/or the number of sources of DC power has to increase. The present inventor has found that providing the electrically conductive members in the form of copper strips that are 16 mm wide and 9 mm deep and having rounded corners, and using a voltage difference between each strip in each pair of 450 volts DC will result in an optimum section of length of around 250 metres. Thus, in that embodiment, each pair of electrically conductive members extends for approximately 250 metres in length.

It will also be understood that the pairs of strips may be shorter or larger than indicated above. For example, for steep ascending inclines, the pairs of strips may be towards the shorter end of the range given above, for example, 100 metres, to limit the current flow in the strips (and associated electricity supply apparatus) to an acceptable level, notwithstanding that there may be an exceptionally high power demand.

Similarly, each strip may be of different dimensions to those given above. For example, the dimensions of each strip may vary from the height and width given above. Indeed, throughout this specification, the dimensions given should be considered to be indicative only and the invention should not be considered to be limited solely to those dimensions.

In one embodiment, electrical power is supplied to each of the pairs of electrically conductive members from the normal electricity grid. As DC power is supplied to the electrically conductive members, the normal alternating current provided by the electricity grid must be transformed and rectified to supply DC electricity of the desired voltage.

The present invention may further include switching means operative to supply DC power to a pair of electrically conductive members when a vehicle is travelling over that pair, with the switching means also being operative to turn off the supply of DC power to a pair of electrically conductive members when no vehicles are travelling over that pair. The normal or default state for the power supply to each pair of conductors is off.

The switching means is suitably operatively associated with a detector means for detecting the presence of a vehicle either about to move onto a pair of conductors or on a pair conductors.

In one embodiment, the detector means detects a coded signal superimposed on the conductors by a vehicle. For example, the coded signal may comprise an oscillating voltage similar to that used by utility companies for control purposes. Such a control signal may have a frequency in the order of 400 kilohertz and a voltage of up to about 4 to 20 volts. It will be understood that the coded signal may utilise different frequencies and different voltages from those given above.

In an embodiment of the present invention, when one section of conductors is turned on, a control signal may be sent to the power supply for the next section of conductors along the path of travel of the vehicle. This control signal sent to the power source for the next section of conductors is used to turn on the power supply to the next section of conductors either shortly before or just as the vehicle arrives at the next section of conductors. Alternatively, the control signal sent to the next section of conductors may turn on the power supply to the next section of conductors at a predetermined time after the power supply to the first set of conductors is activated. The power supply to the next set of conductors is maintained, provided that the next set of conductors detects that the vehicle enters the next set of conductors within a specified time period after the power supply to the next set of conductors has been turned on. In this way, if the vehicle turns off the road and therefore does not enter the next set of conductors, the next set of conductors will not detect the presence of the vehicle and therefore will shut off the power supply shortly after it has been turned on. In this embodiment, the adjacent sections of conductors "talk" to each other and interact with each other to turn on the power supply to each section either just before or just as a vehicle arrives at each section. In some embodiments, a sensor may be located towards the "downstream" end of each pair of strips. The sensor may, for example, be a current flow sensor positioned below or adjacent to one of the electrically conductive strips. When a vehicle is near the end of that section (of electrically conductive strips), the sensor will sense the resultant current flow and then send a signal to the next section of electrically conductive strips to turn on the electricity supply to the next section in anticipation of the imminent arrival. This signal may be sent via cable. The "anticipatory" signal is valid for a short time only, say 2 seconds, and if a vehicle has not arrived at the next section within that time, the next section is turned off.

In another embodiment, the vehicle provides a signal to the turn on the next pair of conductive strips. The signal may be in the form of a coded signal that is superimposed on the next pair of conductive strips.

In some embodiments, the switching means may be arranged such that the signal that is used to turn on the next pair of conductive strips must be larger than a predetermined minimum value in order to activate the switching means and turn on the next pair of conductive strips. In this manner, if the next pair of conductive strips is subject to conditions of high electrical leakage, the signal will be lower than the minimum required to turn on the next pair of strips. This is effective to minimize excessive electrical leakage which could lead to unacceptable power wastage and/or to damage to the transformer/rectifier In a second aspect, the present invention provides a transport system for facilitating road transport, said transport system comprising an electric power supply system for providing power to electrically powered road vehicles in accordance with the first aspect of the present invention and at least one electrically powered road vehicle, said at least one electrically powered road vehicle including at least one conductive pick- up that come into contact with the electrically conductive members as the at least one vehicle travels over the electrically conductive members, whereby the vehicle receives DC electrical power from the electrically conductive members, said DC electrical power providing power to operate an electric motor to drive the vehicle.

Each of the vehicles designed for the transport system in accordance with the second aspect of the present invention has at least one DC powered electric motor thereon. The DC powered electric motor is suitably operated by DC electric energy picked up by the vehicle from the conductors positioned on the road surface.

In some embodiments, the motor may take its power from a DC source but the motor itself may run on AC power. In such embodiments, the vehicle may be provided with inverters to convert the DC power taken from the electrically conductive strips to variable frequency AC power to power the motor and to control its speed and torque.

The power supply system in accordance with the present invention may include a number of gaps. Such gaps may, for example, occur across intersections, at regions of high pedestrian traffic, or in suburban areas where children may play. Furthermore, the electric power supply system will inevitably have outer limits to its reach. In order to enable vehicles to travel through the area where there are no conductors positioned on the road surface, it is desirable that each vehicle is provided with back-up batteries to power the electric motors.

The vehicle may be provided with one or more batteries to store electric energy. The batteries may be charged using electricity received from the electrically conductive strips. In some embodiments, the DC voltage of the electrically conductive strips is such that it is equal to the normal charging voltage of each battery pack in the vehicle. This allows for the vehicle motor to have an essentially seamless transition to and from battery and on-road conductors whenever there is a break and then a resumption of the on-road conductors.

The vehicle may alternatively or additionally be provided with one or more of an on-board charging engine or regenerative braking to allow for recharging of the batteries.

In order for the vehicle to be able to pick up electrical power from the conductors positioned on the road surface, the vehicle may be provided with a pick-up arm located under the vehicle body. The pick-up arm may comprise a flat plate hinged to the vehicle underside. Two pick-up carbon brushes may be bonded to the plate, for example, by an epoxy resin or adhesive. Leads carry the power from/to each brush to the vehicle (to the motor controller and battery pack of the vehicle).

The pick-up arm may be automatically retracted and extended. For example, if the vehicle detects that it is travelling over a pair of electrically conductive members, the pick-up arm may be automatically extended such that the brushes contact the electrically conductive members. In one embodiment, the electrically conductive arm is operated such that if power is lost for more than a predetermined time period, such as from one- half to one second, the pick-up arm is automatically retracted. In other embodiments, the pick-up may be manually operated to move to the down position when the vehicle drives over electrically conductive members. The pickup arm may be automatically retracted when power from the electrically conductive strips is lost for any reason. Regaining contact and power may require a manual selection of pick-up arm to the down position (typically made by the driver of the vehicle) when the vehicle is back over the electrically conductive strips.

The pickup arm or plate may be provided with a protective covering at either end of their role. The protective covering may be, for example, be a butyl rubber coating or a similar coating. The protective coating provides protection to the pickup arm in the event that one end of the pickup arm or plate rubs along the road surface. This may occur, for example, if one side of the pickup arm or plate comes off one of the conductive strips on the road. The down force acting on the pickup arm or plate will then caused the other end of the pickup arm to rub along the road. The protective coating assists in preventing damage to the pickup arm or plate in such circumstances.

As mentioned above, the switching means may be responsive to a coded signal superimposed onto the conductors to thereby cause of conductors to be switched on. The coded signal may be provided via a signal plate attached to the vehicle. The signal plate may be mounted forwardly of the conductive pick-ups. The signal plate may be mounted forwardly of the front wheels of the vehicle. In this manner, the signal plate will come into contact with the next section of conductors before the conductive pick-ups of the vehicle start to travel over those conductors. This will facilitate provision of power supply to the next section of conductors be for all just as the conductive pick-ups of the vehicle starts to travel over the next section of conductors. To minimise or prevent sparking, the coded signal may be supplied through both the signal plate and the at least one conductive pickup. The use of a coded signal in both aspects of the present invention also allows for the possibility of enhanced operation and safety by incorporating an electricity leakage test into the apparatus. In particular, if the electrical leakage from the conductors exceeds an acceptable loss (such as may occur in very wet conditions), it may be dangerous to turn a section of conductors on because, for example, the high leakage could lead to undesirably large power losses or damage the transformers or rectifiers. In these instances, an electrical leakage detection means may be provided to prevent the next section of conductors from turning on. In one embodiment, detection of electrical leakage may occur by requiring the coded signal superimposed on to each section of conductors to exceed a predetermined activation threshold before the next section of conductors will be turned on. In this fashion, superimposing the coded signal onto the conductors will result in the coded signal not exceeding the predetermined threshold if conditions of high electrical leakage are present. Thus, the next section of conductors will not turn on in such situations.

In another aspect, the present invention provides an electric power supply system for providing power to electrically powered road vehicles travelling over a road surface comprising a plurality of pairs of electrically conductive members positioned on a road surface, each of the pairs of electrically conductive members being electrically insulated from the other pairs of electrically conductive members and wherein a vehicle travelling along a road travels over one pair of electrically conductive members and then travels over a next pair of electrically conductive members and so forth, a source of direct current electricity to provide a DC voltage to the pairs of electrically conductive members, and switching means operative to supply DC power to a pair of electrically conductive members when a vehicle is travelling over that pair, the switching means being operative to turn off the supply of DC power to a pair of electrically conductive members when no vehicles are travelling over that pair of electrically conductive members, the switching means being responsive to a signal received from a vehicle to turn on a pair of conductors, the switching means responding to the signal only if the signal exceeds a predetermined minimum value. The signal may be superimposed onto a pair of conductors via a signal plate on a vehicle and the signal superimposed on the conductors is detected and the switching means turns on power supply to the pair of conductors only if the signal exceeds a predetermined minimum value.

The present invention also encompasses a vehicle for use in the transport system as described above.

Other features of the present invention will be described in more detail hereunder with reference to the description of preferred embodiments of the invention, as shown in the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a schematic cross-section view through one copper conductor and insulating base on road bed, suitable for use as one strip in a pair of electrically conductive strips positioned on the road surface in accordance with an embodiment of the present invention;

Figure 2 shows a schematic end view of a vehicle travelling across a pair of electrically conductive strips in accordance with an embodiment of the present invention; Figure 3 shows one possible layout for supplying DC electrical power to a plurality of pairs of electrically conductive members in accordance with an embodiment of the present invention;

Figure 4 shows a schematic view of one possible layout of pairs of electrically conductive members close to a road intersection; and

Figure 5 shows a side view of a vehicle suitable for use in embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

It will be appreciated that the attached drawings have been provided to illustrate preferred embodiments of the present invention. Thus, it will be understood that the present invention should not be considered to be limited solely to those features as shown in the attached drawings.

Turning firstly to figure 1 which shows a cross-sectional view through one copper conductor and insulating base on a road bed, the copper conductor 10 is in the form of a long strip of copper. The copper conductor may have a width of 16 mm at the base and a height of 9 mm. The copper conductor 10 may have rounded shoulders 12. Copper conductor 10 is shown in Figure 1 as being a low profile conductor.

The strip of a copper conductor 10 is laid on an insulating base 14. Insulating base 14 electrically insulates the copper conductor 10 from the road base 16. The insulating base 14 may, for example, comprise an epoxy adhesive that bonds the copper strip to the road base 16 as well as electrically insulating the copper conductor 10 from the road base 16. Alternatively, the copper conductor 10 may be mounted to a strip of insulating material 14 (such as a non-electrically conductive polymeric material) and the insulating material may then be bonded to the road base 16. In Figure 3, the pairs of conductors 24, 25 are provided with a similar power supply as that for pairs of conductors 26, 27. That is, pairs of conductors 24, 25 are connected to an appropriate transformer and rectifier that is similar to transformer and rectifier 32. Pairs of conductors 28, 29 are similarly arranged. Figures 3 and 4 show some possible layouts of pairs of copper conductor strips in accordance with the present invention.

In figure 3, a road 20 having a centre line 22 is provided with pairs of copper conductor strips 24, 25, 26, 27, 28, 29. Each copper conductor strip in each pair is essentially as shown in figure 1. The on-road conductors are divided lengthwise into electrically independent sections., The length of a section depends on the standard voltage chosen and local circumstances. In some embodiments, the length of each pair of copper conductors may fall within the range of 100 to 500 metres, more preferably 200 to 300 metres, with a length of 250 metres being a useful length. The copper conductors in each pair may be spaced apart by approximately 1 metre between their respective inner edges. Rather than having separate insulating bases 14 for each copper conductor 10, a single insulating base 14 may carry both copper conductors. For example, a single insulating coat about 2 metres may underlie the copper strips. This will provide about 500 mm of insulated surface outboard of each conductor. Power is provided to the pairs of conductors from the normal electricity grid.

However, in the present invention, the power that is provided to the conductors is DC power, more suitably low voltage DC power. In order to convert the alternating current electricity supplied from the electricity grid, in the arrangement shown in figure 3, a transformer and rectifier 32 receives electricity from the grid via power lines 33 and this three-phase AC power is converted to DC power by transformer and rectifier 32. The DC power is then sent to the pairs of conductors 26, 27 via lines 35, 34. The transformer and rectifier 32 also include appropriate switching such that each of the pairs of copper conductors 26, 27 can be independently switched on and off. Detectors 38, 39 are used to detect the presence of a vehicle on the conductors. The power to be supplied to each of the pairs of copper conductors should be sufficient such that vehicles travelling over the copper conductors may draw up to 500 kilowatts or so from the system. For the arrangement shown in figure 3, which includes copper conductors having a length of approximately 250 metres, each pair of copper conductors should be able to deliver up to 0.5 megawatts of power to cope with heavy traffic. However, it would be expected that normal output would be under 0.25 megawatts for heavy traffic in both directions on a level road. Thus, transformers need a continuous rating of about 0.25 megawatts and an intermittent rating of 0.5 megawatts. This intermittent rating may be for a period of up to 1 minute. An exception to this could be required for the transformers providing power to copper conductors mounted on long steep climbs, where a continuous rating of 0.5 megawatts may be required. Of course, if greater power is required, a larger number of transformers may be used.

As a further alternative, each transformer and rectifier may provide power to a greater number of pairs of conductors, or to a lesser number of pairs of conductors. Each transformer may have an overload cut-out and re-close switch. This switch suitably operates on the DC side of the transformer. Each DC output line from the transformer may have independent overload switches. The overload cut-out and re-close switches may be set such that if three re-close attempts are unsuccessfully made, the section is shut down and a signal is automatically sent to the control panel to indicate a fault. Vehicles may then proceed across this dead section using an on-board battery power system.

All switching used in the system of the present invention may be solid state switches.

The copper conductors 10 represent bare electric conductors mounted to the surface of a road. A question may be raised as to whether bare electric conductors on a road surface can be safe. In the system of the present invention, they are safe. In particular, the present invention uses mains power but delivers direct current voltage at relatively low volts. Moreover, each copper conductor 10 is insulated from the road surface and from the other copper conductor in its respective pair. Thus, standing on one of the conductors will not complete any circuit and therefore little or no current will flow through the person standing on one of the copper conductors. Further, the DC voltage supply to the conductors is created by transforming and rectifying high voltage, three- phase alternating current to give a positive DC voltage to one conductor and an equal, negative DC voltage to the other conductor in each pair of conductors. This means that the voltage to earth from either conductor is only half the voltage across the conductors. Correspondingly, the voltage available to each vehicle is double that from each conductor to earth. This fact, plus the use of DC rather than AC, contributes to the electrical safety of the system of the present invention. The actual DC voltage that is supplied to the pairs of copper conductors will depend upon several factors. For example, the lower the standard voltage selected, the lower will be the perceived electrical safety risk, the lower will be the actual energy leakage when a road is wet and the conductors are on and the few the number of battery cells by each vehicle to provide an on-board power supply. On the other hand, the weight of copper conductor and/or the number of transformers needed for the on-road installation is inversely proportional to the square of the standard voltage. That is to say, other things being equal, if the voltage is halved, the weight and cost of copper needed will rise fourfold. The present inventor has found that possible standard voltages may lie anywhere between about 100 and 600 volts DC. An acceptable comprise may be between. 300 and 450 volts DC, with 450 volts DC being useful. This means that the voltage supplied to each copper conductor only needs to be 225 volts DC line to earth.

As voltage is reduced, the thickness of the on-road copper conductors and/or the number of transformers/rectifiers has to increase. At a total voltage of about 450 volts DC, the optimum section length of each pair of copper conductors is about 250 metres. With 450 volts DC as a standard voltage, typically for transformers/rectifiers, each of 0.5 megawatts intermittent and 0.25 megawatts continuous rating, will be required per 1 kilometre of road surface. A transformer may serve both "up" and "down" road directions and, in a larger size, multiple lanes, where applicable.

As mentioned earlier, the copper conductors are positioned on the surface of the road. This arrangement is believed to be superior to placing the conductors in underground slots. Placing conductors in underground slots would mean they were not exposed on the road surface and therefore would potentially be electrically safer. However, slots inevitably collect grit and other road detritus, as well as rain or snow that falls on the road. This is difficult to remove and it damages the conductors and the vehicle pick-up mechanism. A slot system is also more costly to install and makes acquiring the conductors by the vehicle pick-up arms more difficult. Inductive systems have also been considered by the present inventor. An inductive system has the advantage that there are no exposed conductors on the road surface, and thus it may appear safer than a conductive system, such as the present invention. However, inductive systems are less energy efficient, much more costly to install on the road, heavier and more costly to install on vehicles, and require intense magnetic fields which may be dangerous to health.

Vehicles travelling over the pairs of copper conductors must be able to pick-up electric power from those conductors. A large number of different designs may be used in this regard. However, one possible design is shown with reference to figure 2. In figure 2, a vehicle 50 having wheels 52, 54, is provided with a plate 56. Plate 56 may, for example, be 1,620 mm wide and 100 mm long. The plate as shown in figure 2 stretches largely across the full width of the vehicle. The plate may be provided with one or more holes to enable air to pass the therethrough to reduce the amount of down force acting on the plate when the vehicle is travelling at speed. The plate 56 carries two electrically conductive brushes 58, 60. A gap 62 is positioned between the brushes 58, 60. As an example, each brush may be 800 mm wide and the gap may be 20 mm wide. The gap 62 may be filled with an electrically insulating material, suitably an insulating material that is somewhat soft and can yield without breaking should it contact an object.

Each end of the plate may be provided with a protective coating, such as a protective butyl rubber coating. This helps protect the ends of the plate in the event that one end of the plate moves off one of the conductive strips. If this occurs, the end of the plate that moves of the conductive strips will be pushed on to the road surface by the force acting on the plate. The protective coating is shown in dotted outline 61 in figure 2.

It is desirable that the width of each brush be somewhat less than the gap between the copper conductors 10 to remove the risk of a brush short circuiting across the conductor pair.

The use of a wide pick-up plate eliminates the need for a lateral traversing mechanism for the pick-up. It also eliminates the need for any device to detect the vehicle's lateral position in relation to the electrically conductive strips. All a driver has to do to achieve initial contact is to drive with the electrically conductive strips somewhere within the vehicle's track and move the pick-up to the down position. Contact will be maintained so long as the electrically conductive strips remain within the vehicle track. Automatic steering may be used to assist in this regard on a longer drive.

The brushes 58, 60 must be able to be lowered onto the conductors or retracted against the underside of the vehicle. To this end, the brushes are mounted on a pair of pantograph arms 64, 66. The pantograph arms keep the plate 56 (and therefore the brushes 58, 60) horizontal. Appropriate electrical connections may be provided to enable the electrical power picked up from each of the brushes 58, 60 to be transferred to the vehicle. The pantograph arms may carry appropriate electrical cables to transfer electric power from the brushes to the vehicles.

During use of the vehicle, when first entering a region of a pair of copper conductors, the driver steers so that both strips of copper conductors 10 in each pair are within the vehicle's wheel tracks and then lowers the pick-up arm. The pick-up arm is lowered either automatically by the vehicle or by the driver. The brushes 58, 60 will then correctly contact the copper conductors 10 and start the transfer of power from the copper conductors 10 to the vehicle. The brushes will remain in contact with the copper conductors over a lateral range equal to the width of the brush (i.e. 800 mm in the example given above). If power is lost (for example, if power is lost for predetermined time, such as more than 0.5 seconds), the pick-up arm may be automatically retracted by the vehicle. The driver may lower it again as and when the vehicle is back over the conductors. Alternatively, the brushes may be automatically lowered once the vehicle detects that it is over the electrically conductive strips.

It is desirable to avoid sparking between the conductors and the pick-up brushes 58, 60. In particular, sparking has several deleterious effects - it causes erosion of both the brushes and the conductors, it can form harmful ozone and/or oxides of nitrogen and it causes radio interference. So that sparking is minimized or not occur as the vehicle goes from one pair of copper conductors to another, the brushes may be sufficiently long to comfortably bridge the gap between one section and the next. This gives an effectively continuous contact between sections, thus eliminating sparking at the end of a section. Of course, in some environments it may be accepted that some sparking will occur. It is also desirable that the pick-up brushes maintain continuous, firm contact with the conductors. This can be achieved by a variety of means, including spring loading, pneumatic pressure, suction between the brushes and conductors etc. The vehicle manufacturers are free to choose the particular means for achieving this aim. It is also desirable to keep the copper conductors clear of debris detritus. Period vacuum sweeping by a specialised vehicle may be used to assist in achieving this outcome. Alternatively, or further, the vehicles travelling over the road may be provided with brushes or air blasts operating on the front of the pick-up arm to clear the copper conductors. This may also assist in clearing of rainwater, which may be lying between the conductors.

As mentioned earlier, the default state of the pairs of copper conductors laid on the road surface is "off. They are turned on when, and only when, a vehicle has arrived at or is about to arrive in that section. In order to detect the arrival or imminent arrival of a vehicle in that section of copper conductors, the vehicles may be provided with a coded signal that becomes superimposed on the conductors when the vehicle is travelling over a section of the copper conductors and the brushes on the vehicle are in contact with the conductors. The coded signal is received by a detector associated with the corresponding transformer station. The detector actuates the switching to power up that particular section of the conductors. The coded signal may, for example, be an oscillating voltage similar to that used by utility companies for control purposes. Its frequency may be in order of 400 kilowatts and may be at a voltage of about 20 volts. The coded signal may be turned on whenever an on-board detector on a vehicle senses that the vehicle is travelling over a section of copper conductors or whenever the pick-up arm is in the down position. The coded signal may be superimposed on the conductive strips by passing the coded signals through the conductive pickups. In another embodiment, a signal plate may be provided that comes into contact with the conductive strips on the road. This signal plate superimposes the coded signal on to the conductive strips. Suitably, the signal plate is positioned forwardly of the conductive pickups, possibly forwardly of the front wheels of the vehicle. This is advantageous in that the signal plate can be turned on the next pair of conductive strips prior to the conductive pickups commencing their travel over the next pair of conductive strips. The coded signal may be provided through both of the signal plate and the least one conductive pickup. In this embodiment, sparking is minimised and electricity supplied to a pair of conductive strips is maintained until the conductive pickups move off without pair.

Furthermore, enhanced safety may follow from this arrangement in that the switching mechanism may be set up such that a minimum activation voltage from the superimposed coded signal is required to turn on the next section of conductors. In situations where there is high electrical leakage, such as in very wet conditions, the signal plate may superimpose the coded signal onto the next section of conductors. If the electrical leakage is too high, the next section will not turn on.

Figure 5 shows one possible embodiment of this arrangement. In figure 5, the vehicle 50 is fitted with conductive pickups 56. Conductive pickups are essentially identical to the conductive pickups shown in figure 2 and need not be described further. The vehicle is also fitted with a signal plate 57. Signal plate 57 may be of generally similar construction to conductive pickups 56. The signal plate 57 may be mounted on a pantograph arrangement 59. As can be seen from figure 5, the signal pick up 57 is located towards the front of the vehicle whilst the conductive pickups 56 located towards the rear of the vehicle. Thus, the signal plate 57 and travels over the next section of conductive strips before the conductive pickups 56 arrive on most conductive strips. This enables the next section of conductive strips to be turned on before the conductive pickups 56 arrive on those conductive strips.

As a further alternative, other detectors may be used. For example, position detectors, such as electric current detectors or detector cables laid across the road surface, may detect the imminent arrival of a vehicle on a particular conductor section and that may be operative to turn on that section of copper conductors.

As a further alternative, the "down-road" transformers may electronically "talk" to "up road" transformers such that the arrival of a vehicle on one section of copper conductors automatically turns on the next section of copper conductors after a predetermined time. The predetermined time may be a set time, or it may be calculated by the detection system determining the speed of a vehicle across the "up-road" section of copper conductors and turning on the next adjacent "down-road" section of conductors at the appropriate time. Alternatively, a sensor located a short distance from the end of one pair of conductors (such as 20 metres from the end) may sense the presence of a vehicle and send a signal for the next pair of conductors to be switched on.

The power supply and switching arrangements may also be set up such that when a vehicle leaves a section of copper conductors (as may be detected by the loss of the coded signal superimposed on the conductors by the vehicle), power on that section of copper conductors switches off after a short interval (typically around one second) unless another signal has already been received from another vehicle or another vehicle is about to enter that section of conductors. If a signal continues to be received on a section beyond the normal vehicle passage time, this is taken to indicate that vehicle is stationary on that section or that the traffic is slowly moving. In this event, the conductors remain switched on, which enables a stationary or slow moving vehicle to continue to draw power from the conductors to run its accessories and/or to top up its batteries.

As mentioned earlier, one possible mode of operation for the system of the present invention involves turning on a down-road section a short time after a vehicle first arrives on an up-road section. If the vehicle is not detected on the down-road section within short intervals, that section may be switched off. When the road is wet and the power to the copper conductors is on, there will be electrical leakage both between the conductors and between each conductor and earth. The extent of the leakage will depend on the conductivity of the rainwater and its average depth across the conductors. When rain first falls, it usually contains a relatively high amount of dissolved aerosols and thus has a relatively low resistivity. However, its depth on the conductors is also low. When heavy rain falls, the dissolved matter will decrease in concentration but water depth on the conductors will be greater. Thus, the leakage potential may not change greatly between light rain and heavy rain.

The system may be designed such that an acceptable maximum leakage figure is designed into each section of copper conductors, with the copper conductors defaulting to the "off position should electrical leakage exceed that acceptable maximum leakage figure. For example, a leakage figure may be set at about 10 kilowatts per section. It will be appreciated that electrical leakage will only occur when the section of copper conductors is supplying power to one or more vehicles. If there is no vehicle on the conductors, the power defaults to "off, and the loss or leakage becomes zero. The use of a superimposed control signal from a vehicle to turn on the conductors, in accordance with some embodiments of the present invention, has a further function in very wet conditions. In such conditions, if the conductors were on, the electrical leakage might exceed an acceptable loss. However, the control signal is also subjected to corresponding electrical leakage, which reduces its strength at the receiver. The activation threshold at the detector/receiver may be set to a level such that when the electrical leakage is greater than that corresponding to an acceptable power loss from each section of conductors, power to the conductors stays off. The appropriate activation threshold will be chosen according to the circumstances of a given area. When the power remains off in such conditions, the vehicle travels under its own on-board battery power. In other embodiments, the switching means may also include provision to supply a small test current to the section of copper strips prior to fully turning on the electricity supply to that section of copper strips. This small current may be used to test the electrical leakage conditions of that section of conductive strips. If the electoral leakage is below an acceptable value, full electricity supply will be turned on. If the electrical leakage is above an acceptable value, full electricity supply will not be turned on.

In some circumstances, parts of a road may flood. On seeing a flooded section, the driver may choose to retract the pick-up arm. If the pick-up arm remains lowered, the control signal from the vehicle may leak to an extent that it falls below the power activation threshold and the power will remain off. Alternatively, the leakage of power from that section of copper conductors may be greater than the acceptable leakage and the power may be switched off to that section. This causes the pick-up arms to automatically retract and the vehicle may proceed using its on-board battery power. Desirably, low-lying sections of road that are subject to frequent flooding suitably do not have copper conductors laid thereon. As another feature of some embodiments of the present invention, vehicles using the system may be provided with an automatic steering function to maintain the collector brushes in contact with the copper conductors. In one embodiment, the magnetic field around the conductors is used. For example, an array of magnetic field sensors may be placed across front and rear of the vehicle. Once the vehicle is drawing power, there is a strong magnetic field in the vicinity of both conductors. The sensors detect this and the midpoint of the two strongest fields is taken as the midpoint of the conductors. Appropriate signals may then be sent to the power steering jack to maintain the vehicle in the correct position. The vehicles designed for use on the system of the present invention are suitably supplied with a battery backup to provide on-board power in instances where the vehicle is travelling across roads that do not have the copper conductors fitted thereto. For example, the on-road conductors can cross intersections and each other, but they may not necessarily be fitted in such locations. One example of this is shown schematically in figure 4, in which respective pairs of copper conductors 70A, 7OB, 72A, 72B, 74A, 74B, 76A and 76B each finish short of a road intersection 80. This is done in anticipation of pedestrian traffic crossing the road at intersection 80. To provide motive power in such circumstances, the vehicles may be provided with an on-board battery pack. The battery pack may be automatically recharged while the vehicle is drawing its power from the copper conductors. It may also be recharged when a vehicle uses regenerative braking. Ideally, the battery pack could provide for a minimum of 20 kilometres of autonomous travel. However, larger battery packs may also be provided. The vehicles may also be provided with an on-board charging engine as in current hybrid vehicles. Of course, the on-board battery packs may be recharged overnight by plugging into an appropriate recharger connected to the mains power supply.

Embodiments of the present invention also envisage a number of different methods for charging for electricity consumption. At one end of the scale, vehicles may pay a flat fee for a particular period (e.g. annual or monthly fee) related to their size and type of vehicle. This fee may entitle them to unlimited energy use. At the other end of the scale, vehicles may be fitted with sophisticated metering units which take into account the location and time of day in determining the unit rate to be charged. In between, vehicles may pay a monthly charge dependent on vehicle power and the distance traveled during the month.

Each vehicle may have a meter which records the name of the supply utility. Payment may then be made to a variety of utilities. However, it would be better if there was a sharing arrangement where a vehicle pays one bill to its "home" or nominated utility and the utilities then adjust payments between themselves.

The present invention may assist in enhancing road safety. Obviously, if a person or another vehicle is struck by a vehicle using the system of the present invention, the result will be similar to being hit by a conventional vehicle. However, the system of the present invention imposes strong lane discipline on electrical vehicles because power reduces when a vehicle is out of lane. If automatic steering is implemented this discipline is enhanced. It also enhances lane discipline in low visibility conditions such as fog. This lane discipline diminishes the worst kind of accident in which vehicles collide head on or leave the road and strike objects such as trees. In areas where pedestrians are likely to congregate, the availability of battery power only moderates speeds in those places.

With regard to electrical safety, the idea of having live conductors on the surface of a road may seem quite unsafe, but this is not so. In particular, the conductors will be on only when a vehicle is using the section or is immediately about to do so. The conductors are also set at foot level and, at 225/450 volts DC, will not harm people who walk thereon even in wet conditions. Anyone who deliberately tries to electrocute himself or herself by laying one hand on each conductor will be killed or injured by the oncoming vehicle rather than electrocuted. Animals, domestic or wild, can cross in safety when no vehicles are present as the conductors will then be off. The copper conductors will not be paid in places where children may play in the streets, such as local housing areas, nor where pedestrians regularly cross, for example, at traffic lights. In those places, vehicles will travel using their on-board battery packs or other forms of power, such as internal combustion engines, compressed air engines, etc.

In much of the world, roads are under snow and ice for a considerable part of the year. The system of the present invention is compatible with the use of snow ploughs and blowers, although care should be taken to not bank up snow over or against the conductors. In cold climates, it may also be possible to incorporate an electrical heating tape beside each conductor to aid the clean removal of snow and ice in winter time. Care should be taken to avoid splash of road salt and slush against the conductors.

The system of the present invention will cost approximately US$55,000 to install per kilometre, based on copper prices current in November 2006. The capital cost of electricity supply, including the roadside transformers, rectifiers, detectors and control systems, will be additional to this. However, the overall energy consumption will be about two-thirds of an equivalent conventional vehicle fleet. Crude oil requirements will be negligible. Road usage world- wide follows a variant of the "80/20" rule. In the United

States, for example, there are some 4,000,000 miles of public roads but 85% of all traffic miles are driven on 1,000,000 miles of those roads. In other roads, 85% of driving in the United States occurs on 25% of the roads. The urban arterial/freeway road system in the USA accounts for under 2% of the total road mileage but carries over 35% of total USA road traffic miles. Thus, it is possible to make a big impact on energy efficiency and urban pollution by installing a relatively small mileage of roads with the system of the present invention.

The system of the present invention functions to deliver, in some embodiments, up to 500 kilowatts of electrical power to each suitably equipped vehicle on the road. Subject to the vehicle's ability to receive this power, makers can design and construct their models as they see fit. The system of the present invention can supply electric power to any kind of vehicle, from mini cars to the heaviest trucks. The system of the present invention offers high vehicle performance and low carrying capacity, acceleration, top speed and hill climbing ability. The system of the present invention improves the overall energy efficiency of the road fleet. This arises from using electric traction and simple, conductive electric transmission. The total energy consumed by a given fleet will be less than 70% of that same fleet using conventional internal combustion engines. The system of the present invention frees vehicle from crude oil dependence and allows them to run on electricity generated by solar, wind, wave, hydro, geothermal, natural gas, nuclear or coal power sources. Unlike most electric vehicle proposals, the system of the present invention is not confined to cars. It is also suitable to heavy goods vehicles and buses. Such vehicles are usually diesel powered and their emissions may be harmful to health. Converting such vehicles to electric power may thus benefit the health of many in addition to the other benefits arising from the present invention.

In order to deter theft of copper from the road surface, the copper conductor may have moderate amounts of tracer elements incorporated in it. This will enable ready tracing of any stolen copper.

The present invention provides a system for delivering electric power to vehicles that has enhanced safety over the system shown in my earlier Australian Patent No. 712902. The system enables reduction in energy costs and the wider implementation of electric powered vehicles.

The following description refers to the most preferred embodiment of the present invention. The present invention provides an integrated system of powering road vehicles of all types and sizes by electricity from public utilities supplied on-road and on demand to any suitably equipped vehicle. The vehicles may be of any type or size including the largest trucks or busses; they share any road with any combination of conventionally- powered vehicles. The electricity may be generated by any means including solar, wind, nuclear or fossil fuel.

Widespread adoption of the present invention will cure "crude oil addiction", mitigate "global warming" and reduce urban pollution.

The total energy consumption of any given vehicle fleet used in the present invention is some 30% less than that of its conventionally powered counterpart.

Supply is via two electrically conductive strips lying parallel to each other, approximately half a vehicle's width apart, that is about 1 metre, and running lengthwise along the middle of a lane on any sealed road. The strips may be of any material having the requisite very high electrical conductivity including surface conductivity, corrosion resistance and mechanical strength but typically will be of copper of the order of 2 centimetres wide and 1 centimetre high.

The strips are laid directly on the road surface using bitumen with suitable additives as insulator and adhesive; the road surface on which the strips are laid must be level between the strips.

The strips are sufficiently small so as not impede free use of the road by all existing users thus conventional and electric vehicles share the road.

Each pair of strips is divided lengthwise along the road into electrically independent sections; the length of those sections varies with local circumstances but typically is some 250 metres.

Electricity is supplied to the strips from conventional high voltage AC power lines running adjacent to the road and, at intervals corresponding to the section lengths above, supplying DC power from transformer/rectifiers to the copper strips at the section mid- point lengthwise.

The DC voltage between each strip must be standard over a very wide area, preferably standard world wide; it must be equal to the charging voltage of the auxiliary battery pack carried on each vehicle; the standard must lie between 100 and 600 volts DC; the preferred figure is 450 volts DC. The circuitry of the transformer/rectifiers is so arranged that one strip is half the total voltage positive in relation to earth and the other is half the total voltage negative in relation to earth.

The electrical components are so sized as to be able to deliver up to 500 KW to one vehicle using the system; normal demand per vehicle is but a fraction of that figure. The default electrical state of any section is OFF; it comes ON only when a coded signal from a vehicle on the section is being received.

All users of a road equipped with the present invention are as 'safe' or safer than they are when using a road with conventionally powered vehicles only; given that conventional road traffic causes some 1.2 million deaths world wide each year and many times that number of disabling injuries 'safe' in the context of road traffic is a qualified term.

Each vehicle used in the present invention can pick up electrical power from the on-road conductors. Each vehicle carries a battery pack to give it at least 20 km of autonomous travel in places where the conductors are not fitted; all vehicle batteries may be recharged while stationary via a plug-in from the mains supply.

For particular models vehicle manufacturers may choose to fit a larger battery pack giving greater autonomous range and/or to fit an internal-combustion-engine- powered auxiliary charger. The charging voltage of the battery pack is equal to the conductor DC voltage for three reasons: so that the battery is automatically topped-up whenever the vehicle is over conductors; so that the vehicle can transition seamlessly from conductor power to battery power or vice versa and to obviate the need for an on-vehicle transformer to match the voltages were they different. Each vehicle for use in the present invention has a pick-up plate under its body; the plate may remain retracted under the body or may be extended to contact the conductors and collect power; this may be done manually or may happen automatically.

The plate is typically the full overall width of the vehicle; its lower face is of conductive carbon which runs along the conductors and receives electrical power from the positive and negative conductor respectively; the conductive carbon is in two sections

- one to the left and the other to the right of the plate; the sections are electrically insulated one from the other; the width of each section is somewhat less than the distance between the inner edges of the conductors - this is to obviate possible shorting across the conductors; this permits the vehicle to move considerably to left or right in relation to the conductors as it travels along the road while still maintaining electrical contact.

When in contact the plate is held firmly against the conductors by hydraulic, pneumatic or other force on its arms; the plate is 'flying' very close to the road surface so at high speeds, say 160 kph and over, the Bernoulli Effect will increase the down force to levels that may be too high; to obviate this a plate on a fast vehicle has holes through it to relieve the suction.

The length of the plate from front to back is somewhat greater than the insulating gap between successive conductor sections; if the plate lost contact with one section before obtaining contact with the next section sparking would result; sparking has many detrimental effects but they are avoided by this arrangement.

As and when a vehicle moves off the conductors external power is lost and the vehicle proceeds on the power of its batteries; when this happens the contact plate is automatically retracted; immediately prior to retraction the plate will be in contact with one conductor only and will tilt over to one side onto the road surface; to protect it from damage in those circumstances each end of the plate has a butyl rubber, or similar, covering.

In order that power from the battery does not 'leak' to the conductors (in the event of an unusually low conductor voltage) the positive and negative leads from the plate both have 'one- way' diodes to prevent this from happening.

A section is turned ON when a coded signal from a vehicle over the section is received at the corresponding transformer/rectifier switch sensor; the signal is a high frequency AC voltage superimposed on the conductors; its voltage is of the order of 20 volts. The signal is transmitted from a vehicle by two means; firstly from the pick-up plate itself and secondly from another signal plate located just forward of the front axle.

The purpose of the forward plate is to ensure that a section which the vehicle is about to enter is ON before the pick-up plate arrives; this gives a smooth transition from section to section; it also obviates sparking From time to time a road will be wet or even flooded; when the road is wet and a section is ON there will be electrical leakage between the conductors and between each conductor and earth; the amount of the leakage will depend on the conductivity of the water on the road; in turn this will depend on the depth of the water and the concentration of ions in solution; to avoid excessive power wastage there must be limit to this loss; the limit will be determined by local circumstances but it may be of the order of 10KW; note that the default condition of a section is OFF and then there is no energy loss.

The coded signal has a second purpose which is to test whether or not power wastage will be too high before the section is turned ON; if the road is wet the coded signal itself will be subject to loss and the voltage received by the sensor at the transformer/rectifier will be reduced; setting the activation level of the sensor appropriately ensures that if the power loss would be excessive the section does not come ON; the vehicle then proceeds on its battery power.

In conditions of snow or ice the road can be snow-ploughed just as any other road; where such conditions are common an electrical heating element may be run under the conductors to help melt the ice; road-salt must not, in any circumstances, be used on a road equipped with the present invention.

Design of an installation in accordance with the present invention is supported by a proprietary software module which is an integral part of this invention. Those skilled in the art will appreciate that the present invention may be susceptible to variations and modifications other than those specifically described. It is to be understood that the present invention encompasses all such variations and modifications that fall within each spirit and scope.

Claims

Claims:

1. An electric power supply system for providing power to electrically powered road vehicles travelling over a road surface comprising a plurality of pairs of electrically conductive members positioned on a road surface, each of the pairs of electrically conductive members being electrically insulated from the other pairs of electrically conductive members and wherein a vehicle travelling along a road travels over one pair of electrically conductive members and then travels over a next pair of electrically conductive members and so forth, a source of direct current electricity to provide a DC voltage to the pairs of electrically conductive members, and switching means operative to supply DC power to a pair of electrically conductive members when a vehicle is travelling over that pair, the switching means being operative to turn off the supply of DC power to a pair of electrically conductive members when no vehicles are travelling over that pair of electrically conductive members.

2. An electric power supply system as claimed in claim 1 wherein the DC voltage difference between each conductor in a pair of conductors does not exceed 600 volts.

3. An electric power supply system as claimed in claim 2 wherein the DC voltage difference between each conductor in a pair of conductors does not exceed about 450 volts.

4. An electric power supply system as claimed in claim 1 wherein the electrically conductive members are arranged such that a vehicle travelling over the electrically conductive members picks up electrical power from the conductive members by contact elements on the vehicle coming into contact with the electrically conductive members.

5. An electric power supply system as claimed in claim 1 wherein the electrically conductive members comprise strips of electrically conductive material and the electrically conductive strips are generally parallel to each other.

6. An electric power supply system as claimed in claim 1 wherein the electrically conductive strips are positioned on the road such that they are insulated from each other and from earth (the road surface).

7. An electric power supply system as claimed in claim 6 wherein the electrically conductive members are laid on an adhesive insulating base which insulates them from each other.

8. An electric power supply system as claimed in claim 7 wherein the electrically conductive strips are bonded to the road surface by an epoxy adhesive.

9. An electric power supply system as claimed in claim 7 wherein the electrically conductive strips are bonded to tiles that are then placed in or on the road surface.

10. An electric power supply system as claimed in claim 1 wherein each pair of strips is provided with a dedicated source of direct current power.

11. An electric power supply system as claimed in claim 1 wherein a source of direct current power provides direct current electricity to two or more pairs of strips.

12. An electric power supply system as claimed in claim 1 wherein each pair of strips has a length of from 50 metres to 500 metres.

13. An electric power supply system as claimed in claim 12 wherein each pair of strips has a length of around 250 metres.

14. An electric power supply system as claimed in claim 1 wherein electrical power is supplied to each of the pairs of electrically conductive members from the normal electricity grid and normal alternating current provided by the electricity grid is transformed and rectified to supply DC electricity of a desired voltage.

15. An electric power supply system as claimed in claim 1 further including switching means operative to supply DC power to a pair of electrically conductive members when a vehicle is travelling over that pair, with the switching means also being operative to turn off the supply of DC power to a pair of electrically conductive members when no vehicles are travelling over that pair.

16. An electric power supply system as claimed in claim 1 wherein the normal or default state for the power supply to each pair of conductors is "off.

17. An electric power supply system as claimed in claim 1 wherein the switching means is operatively associated with a detector means for detecting the presence of a vehicle either about to move onto a pair of conductors or on a pair conductors.

18. An electric power supply system as claimed in claim 17 wherein the detector means detects a signal superimposed on the conductors by a vehicle.

19. An electric power supply system as claimed in claim 15 wherein when one section of conductors is turned on, a control signal is sent to the power supply for the next section of conductors along the path of travel of the vehicle, said control signal sent to the power source for the next section of conductors being used to turn on the power supply to the next section of conductors either shortly before or just as the vehicle arrives at the next section of conductors.

20. A transport system for facilitating road transport, said transport system comprising an electric power supply system for providing power to electrically powered road vehicles in accordance with any one of the preceding claims and at least one electrically powered road vehicle, said at least one electrically powered road vehicle including at least one conductive pick-up that comes into contact with the electrically conductive members as the at least one vehicle travels over the electrically conductive members, whereby the vehicle receives DC electrical power from the electrically conductive members, said DC electrical power providing power to operate an electric motor to drive the vehicle.

21. A transport system as claimed in claim 20 wherein the at least one vehicle has at least one DC powered electric motor thereon.

22. A transport system as claimed in claim 20 wherein the electric motor takes its power from a DC source but the motor itself runs on AC power and the at least one vehicle is provided with inverters to convert the DC power taken from the electrically conductive strips to variable frequency AC power to power the motor.

23. A transport system as claimed in claim 20 wherein the at least one vehicle is provided with one or more back-up batteries to power the electric motor.

24. A transport system as claimed in claim 23 wherein the one or more batteries are charged using electricity received from the electrically conductive strips.

25. A transport system as claimed in claim 24 wherein the DC voltage of the electrically conductive strips is such that it is equal to a normal charging voltage of the one or more batteries in the vehicle.

26. A transport system as claimed in claim 20 wherein the at least one vehicle is provided with a pick-up arm located under the vehicle body.

27. A transport system as claimed in claim 26 wherein the pick-up arm comprises a flat plate having two pick-up carbon brushes bonded to the plate.

28. A transport system as claimed in claim 20 wherein the at least one conductive pick-up is automatically retracted and extended.

29. A transport system as claimed in claim 28 wherein the at least one conductive pick-up is operated such that if power is lost for more than a predetermined time period the at least one conductive pick-up is automatically retracted.

30. A transport system as claimed in claim 20 wherein the at least one conductive pick-up is manually operated to move to the down position when the vehicle drives over electrically conductive members

31. A transport system as claimed in claim 20 wherein the switching means are responsive to a signal superimposed onto the conductors to thereby cause of conductors to be switched on and the signal is provided via a signal plate attached to the vehicle.

32. A transport system as claimed in claim 31 wherein the signal plate is mounted forwardly of the at least one conductive pick-up.

33. A transport system as claimed in claim 31 wherein the switching means is responsive to a signal received from a vehicle to turn on a pair of conductors, the switching means responding to the signal only if the signal exceeds a predetermined minimum value.

34. An electric power supply system for providing power to electrically powered road vehicles travelling over a road surface comprising a plurality of pairs of electrically conductive members positioned on a road surface, each of the pairs of electrically conductive members being electrically insulated from the other pairs of electrically conductive members and wherein a vehicle travelling along a road travels over one pair of electrically conductive members and then travels over a next pair of electrically conductive members and so forth, a source of direct current electricity to provide a DC voltage to the pairs of electrically conductive members, and switching means operative to supply DC power to a pair of electrically conductive members when a vehicle is travelling over that pair, the switching means being operative to turn off the supply of DC power to a pair of electrically conductive members when no vehicles are travelling over that pair of electrically conductive members, the switching means being responsive to a signal received from a vehicle to turn on a pair of conductors, the switching means responding to the signal only if the signal exceeds a predetermined minimum value.

35. A system as claimed in claim 34 wherein the signal is superimposed onto a pair of conductors via a signal plate on a vehicle and the signal superimposed on the conductors is detected and the switching means turns on power supply to the pair of conductors only if the signal exceeds a predetermined minimum value.