WO2002101411A2

WO2002101411A2 - Inspection system

Info

Publication number: WO2002101411A2
Application number: PCT/GB2002/002653
Authority: WO
Inventors: Kevin Paul Burgess; Leonard Hallows
Original assignee: Vantage Systems Limited
Priority date: 2001-06-11
Filing date: 2002-06-07
Publication date: 2002-12-19
Also published as: GB0114106D0; AU2002310617A1; WO2002101411A3

Abstract

An inspection system (10) is provided for inspecting a carriageway (11), such as a runway for aircraft (12), or other types of carriageway or surface, such as a motor racing circuit or any surface used by vehicles (34). The inspection system (10) comprises a series of transmitter/sensor receiving devices (13/14), in this case in a common housing or separate housings (13, 14). Each transmitter device (13) transmits a laser or other type of scanning signal (15) to scan an area (16) of the carriageway (11) and be received by a respective sensor (14). The sensor (14) sends an output signal (19) to an indicator device (20, 23) whose display indicates when the scanning signal (15) impinges on an object (17) on the carriageway (11). This can trigger an alarm (32) and/or alert a controller to take appropriate action. The system (10) includes cameras (24) that are provided to allow close visual inspection of the detected object (17).

Description

INSPECTION SYSTEM

The invention relates to an inspection system, and in particular to a system for inspecting carriageways. Carriageways refers to airport runways, taxiways or aprons, motor racing circuits or similar carriageways, or indeed any other surface over which aeroplanes or vehicles of any description may travel. The purpose of such inspection is to detect debris, such as miscellaneous aircraft or other vehicle debris, various foreign objects, stones, dead animals and birds etc. (referred to within the aircraft industry as foreign object debris), that has been deposited on the carriageway inadvertently either by aircraft or any other type of vehicle using the carriageway, or by any other means.

The intention of the invention when in use at airports is to address the problem of pieces of debris being deposited on runways, taxiways and other areas, as an inevitable consequence of the frequent take-off, landing and taxiing of aircraft at busy airports throughout the world. Any form of debris can represent considerable danger to an aircraft tyre bearing the stresses of take-off or landing, as indeed it can to any other type of vehicle travelling along a carriageway. In the case of aircraft, in addition to the danger of tyre bursts, debris can be sucked into engine intakes, and so on. A tragic crash in Paris in 2000 served to underline the threat. It is believed that debris from an aircraft that had just taken off caused a tyre burst to occur on an aircraft subsequently using the same runway. This resulted in the rupture of the second aircraft's fuel tanks, causing it to crash with considerable loss of life. Airlines are legally responsible for any parts that drop from their aircraft. There have been many reports over the last twenty years of tyre bursts caused by tyres striking debris on the runway, fortunately not all resulting in the serious consequences described above. Currently, inspection of runways is carried out visually by airport staff travelling in a motor vehicle at specified intervals. Airports are only required by law to carry out these inspections of runways once every 24 hours, although some airports inspect more frequently, perhaps once every 4 or 6 hours. These visual inspections are also for inspecting the state of the surface of the runway, standing water, cracks in the runway or the like. However, under such an intermittent inspection regime, debris may lie or a defect may remain undetected whilst several aircraft use the runway after the previous inspection, putting those aircraft, their crew and passengers at risk. In addition, small items of debris on, or defects in, a runway or taxiway may be difficult to see by human eye from a motor vehicle, particularly in adverse weather conditions, and may go undetected for a considerable length of time. Furthermore the runway or taxiway cannot be used whilst these inspections are being carried out. Similar risks are inherent at motor racing circuits and possibly other carriageways. Conventional radar systems do not detect the objects concerned, existing Surface Movement Radar (SMR) systems have blind spots, conventional vision systems are inadequate and thermal systems may not detect the correct objects. There is a requirement of the aviation authorities for an improved method of carriageway inspection, and an additional requirement for vehicle movement classification.

It is an object of the invention to provide an inspection system that monitors a carriageway in order to minimise the length of time that debris deposited thereon or defects therein remain undetected. It is also desired to provide an inspection system that can operate without disruption to the use of the carriageway by aircraft or any other type of vehicle.

The invention provides an inspection system for monitoring a carriageway, comprising a transmitter device and a sensor disposed relative to each other in use such that a scanning signal transmitted from the transmitting device scans a predetermined area of the carriageway and is received by the sensor, and an indicating device operative in response to an output signal from the sensor to indicate an irregularity in the scanning signal received by the sensor.

Such irregularity may be caused by some foreign object debris or other debris, an excess of surface water or snow, or a defect in the surface of the carriageway in the path of the scanning signal. Preferably, the inspection system is a continuous system.

The transmitter device may transmit and the sensor may be adapted to receive a laser scanning signal, a radar scanning signal, a sonar scanning signal, and/or an other optical scanning signal or other suitable type of signal. The transmitter may transmit a laser signal at frequencies outside the visible light spectrum, and may transmit a signal at infra-red or ultra violet frequencies, or a combination of infra-red and ultra violet frequencies. The system may comprise a housing in which the transmitter device is mounted, and the sensor may be mounted in the housing. Alternatively, the transmitter device may be mounted in a transmitter housing and the sensor may be mounted in a sensor housing spaced from the transmitter housing. In this case, the transmitter housing and the sensor housing may be disposed on opposed sides of the carriageway. Each housing may be frangible, and may be of concrete/cement. Each housing may be mounted on the ground so as to be retractable on impact, or may be partially within the ground and partially exposed above ground. Each housing may be tubular and up to 100 cm in height. Each housing may be movable about theodolite-controlled axes. The housings may be of a modular design, (with 'plug and play' electronics) making them easy to install for use at airports with runways and taxiways of a variety of sizes and lengths or for use at other locations in monitoring other carriageways being traversed by any other type of vehicle. The system may comprise a plurality of transmitter devices and respective sensors, in spaced disposition along one side, or along both sides of the carriageway. The housings may be disposed to monitor the entire area of the carriageway, or a predetermined portion thereof as required. The housings may be disposed whereby the predetermined area scanned by each housing overlaps that of an adjacent housing, thereby building redundancy into the system. The plurality of sensors may be connected to at least one common indicating device, in which case the or each indicating device may be adapted to indicate the output signal from each of the sensors in succession. The or each indicating device may be programmable to cycle through a display of a plurality of items of debris and/or surface defects in sequence.

The inspection system may comprise a calibration target object, whereby the sensor is adapted to produce a calibration output signal when the scanning signal impinges on the target object, the indicating device being operative in response to the calibration output signal to indicate the location of the target object for calibration of the system. The positioning of an object, (including the calibration target object, foreign object debris, aircraft or vehicle), may be determined using a Global Positioning System (GPS), which may be a Differential Global Positioning System (DGPS).

Alternatively, the transmitting device and the sensor may be mounted on a carrier adapted to traverse substantially the length of the carriageway. The carrier may comprise at least one floating mechanism supporting the transmitting device and the sensor. The carrier may comprise a carrier bar dimensioned substantially to span the width of the carriageway. The carrier bar may be supported at each end by a support. Each support may comprise a floating mechanism supporting the carrier bar. The carrier may comprise motive power means for its propulsion. In the case of the carrier having a carrier bar, both supports may be equally powered, so as to propel the carrier bar at substantially 90° to the sides of the carriageway. The carrier may comprise wheels operable to travel along a side of the carriageway. The wheels may be mounted to a monorail. The monorail track may be buried beneath the surface of the ground so as not to constitute an obstacle in its own right. A monorail track may be disposed along each side of the carriageway. Alternatively, the wheels may be designed to run along the ground itself independently of rails and the carrier controlled to run parallel with the side of the carriageway.

The carrier may be controlled to run between positions substantially at the ends of the carriageway. Alternatively a plurality of carriers, spaced longitudinally of the carriageway and running in conjunction with one another, may be provided to sweep the carriageway, sector by sector. In this case, where some of the carriers having carrier bars will finish each sweep within the length of the carriageway, the carrier bars may be hinged on one of their supports and operable to pivot across the carriageway to extend parallel therewith. Each carrier bar may then slide into a recess provided for the purpose in the ground to the side of the carriageway, so as not to cause any obstacle to the safe passage of an aircraft or other vehicle using the carriageway. A recess may be disposed to extend parallel with the side of the carriageway. As a further alternative, the carrier may be mounted at the front of a vehicle providing the motive power means. In this case, the carrier may comprise a carrier bar mounted on the vehicle to extend substantially equally to either side thereof. The vehicle may be manned or unmanned, and if unmanned, controlled remotely to travel along the centre of the carriageway.

The or each indicating device may be disposed at a location remote from the or each sensor, and may comprise a computing device. The output signal from the or each sensor may be transmitted to the remote location or locations via a networking system comprising of a series of connections by which data is be transmitted to the or each computing device. The or each computing device may comprise a single or duplex hardware configuration. The or each indicating device may give zero indication unless an output signal from the sensor indicates an irregularity in the scanning signal received by the sensor. The or each indicating device may comprise an alarm operable on receiving an output signal indicating an irregularity in the scanning signal received by a sensor. The alarm may provide an audible and/or a visual signal. The inspection system may comprise a camera to provide images of an irregularity detected by a sensor. The camera may be mounted on a tower disposed spaced from the carriageway. The or each indicating device may provide a graphic, photographic, video, infra red and/or thermal image corresponding with the irregularity, or some other type of visual or audio indication. The inspection system may also comprise a bird-scaring device activated when the signal received by a sensor has a temporary irregularity. The inspection system may also comprise a temperature sensing device operable to sense the temperature of the surface of the carriageway, or the atmosphere immediately above it, and transmit a signal dependent on the sensed temperature to the indicating device. The system may also be configured to transmit other information such as wind and humidity and/or other data, in order to transmit useful information to the operator with a view to indicating whether de-icings should take place. The indicating device may be programmed to display a real-time log of events to facilitate identification of the source of any object found, and data as to the response time of the operator to a given incidence of detected foreign object debris. The inspection system may comprise communication means whereby a person may be directed to an object that has been detected. The inspection system may have a cut-off device operable when the inspection system detects a predetermined moving object in the predetermined area of the carriageway. The invention may comprise an inspection system for monitoring a carriageway as specified above in combination with an SMR system. The inspection system may have a cut-off device operable when the SMR system detects a moving object in the predetermined area of the carriageway, and/or the moving object may itself have means for disabling the system during such movement.

The invention will now be described with reference to the accompanying drawings, in which Fig. 1 is a diagrammatic illustration of one embodiment, and Fig. 2 is a diagrammatic illustration of a second embodiment.

Referring now to Fig. 1, there is shown an inspection system 10 for inspecting a carriageway 11, in this case a runway for aircraft 12. However, the system 10 is suitable for inspecting other types of carriageway or surface, such as a motor racing circuit or any surface used by vehicles. The inspection system 10 comprises a series of transmitter/sensor receiving devices 13/14, in this case in a common housing 13, 14. Each transmitter device 13 transmits a scanning signal 15. The transmitted scanning signal 15 may be a laser scanning signal, of sufficiently low power as to make it eye-safe, but alternatively or in addition could be lidar or ladar, laser radar, a radar scanning signal, a sonar scanning signal an other optical scanning signal and/or any other suitable type of signal. Preferable options are, singly or in combination, laser (continuous wave, pulsed or gated laser), laser 'radar', camera and laser linked, or ultra-violet (UV) system. Although millimetric wave radar (MMWR) is a possible option, it is costly and the output is complex, hence other options are preferred. The transmitter devices may transmit a red, green or other frequency laser signal 15. Preferably however, the transmitter devices 13 transmit a laser signal 15 at frequencies outside the visible light spectrum, for example at infra-red, deep infra-red or ultra violet frequencies, or a combination of infra-red and ultra violet frequencies. Such signals will be invisible to pilots. The system uses a type of template to compare what is sensed with what should be seen. The template of reference used can be from various times, the same day or some weeks previously, according to the circumstance. The housings may also include other types of sensors, such infrared, as may be required in order to supply relevant information about the presence of excess standing water or snow on the carriageway surface. The housing may be movable about theodolite-controlled axes whereby each scanning signal 15 scans a predetermined area 16 of the carriageway 11. The predetermined area 16 scanned by each scanning signal 15 overlaps that from an adjacent housing 13, possibly by as much as 50%, thereby building redundancy into the system 10. If the signal 15 detects an object or surface defect 17, the reflected signal 18 is received by the sensor 14. The sensor 14 sends an output signal 19 to an indicating device 20, 23. The indicating device 20, 23 is operative in response to the output signal 19 to indicate the reflected signal 18 received by the sensor 14 caused by the object or surface defect 17. A back-up indicating device 21 may be provided, also to receive the indicating signals 19. The runway 11 is divided into a grid arrangement 22 so that the location of the object or surface defect 17 is indicated in the indicating device 20,

23. Depending on the type of scanning signal 15, a pictorial representation of the object or defect 17 may be displayed on a screen 23 of the indicating device 20, 23. Preferably, the screen 23 shows no image unless an object or defect 17 is detected by the sensor 14. In the embodiment shown, the cameras 24 are located on towers 33 that are set back from the runway 11, but they may be placed inside the sensor housings 13, 14, alongside the laser transmitter, or may be ground mounted if preferred. These cameras 24 may be directed at an article of debris 17 as detected by the sensors 14 to enable more detailed inspection of the debris 17 by an operator. One camera 24 for every five transmitting devices 13 and sensors

14 may be adequate for this purpose. Such cameras 24 can zoom in on any debris 17 so as to give the operator a good image of that debris 17 so that an informed decision can be made as to the action required. The indicating device 20, 23 is preferably programmed to indicate the output signal 19 from each of the sensors 14 in succession (or may show a composite image or graphic made up of the output of a range of sensors). To cater for the event of more than one item of debris or defect 17 being detected, the indicating device 20, 23 may be programmable to cycle through a display of each item of debris and/or defect 17 in sequence.

Transmitting devices 13 and sensors 14 may be disposed on one side or on both sides of the runway 11 in order to provide blanket coverage of the runway 11. Alternatively, each sensor 14 may be disposed in its own housing and located spaced from the respective transmitting device 13, for example on the opposite side of the runway 11. In this case the sensor 14 will detect the 'shadow' of the object 17 since the signal received by the sensor 14 will be zero or at least there will be an irregularity in the scanning signal 15. The inspection system 10 also incorporates a bird-scaring device 35 activated when the signal received by a sensor 14 has a temporary irregularity, for example due to the presence of a bird or animal, for example through the heat signature or similar. In that case, the system operator may direct a human bird-deterrence team directly to the location of bird or wildlife incursion, as is regarded desirable by airport authorities. The inspection system 10 may also incorporate a temperature sensing device 36 operable to sense the temperature of the surface of the runway 11 (or just above it) and transmit a signal dependent on the sensed temperature to the indicating device 20, 23, thereby alerting the controller to the possibility of ice on the runway 11 or melting of the surface. It is possible to incorporate historical data within the software display so as to build up a predictability graph to indicate when de-icings will be best carried out. Saving of unnecessary de-icings has been stated as a big cost advantage to airports of deploying the system of the invention, as opposed to using their present inaccurate in-built runway temperature sensors or primitive 'boot kicking the tarmac' approach. When a calibration target object 37 receives a signal 15, it produces a calibration signal, and the indicating device 20,

23 is operative in response to the calibration signal from the target object 37 to indicate its location for calibration of the system 10. The positioning of an object 17, 37 can be determined using the Differential Global Positioning System (DGPS) or other Global

Positioning System (GPS).

The housings 13, 14 are either frangible, perhaps made of concrete/cement or other such frangible material, so as not to present a danger to any aircraft 12 or other vehicle colliding with them, or retractable into the ground for the same purpose. The housings 13, 14 are tubular, at least partially filled with sand to render them vibration stable, and are up to 100 cm in height. The housings 13, 14 may have heating and/or cooling means incorporated within them to maintain the electronic equipment at a stable working temperature.

Referring now to Fig. 2, there is shown an inspection system 25 for inspecting a runway 11 for aircraft 12. The system 25 is similar to the system 10 in many respects, and corresponding parts are identified by the same reference numerals. In this embodiment, however, the combined transmitter device 13 and sensing device 14 is, or two devices 13, 14 as showη are, mounted on a carrier bar 26 of a carrier 27 adapted to traverse the length of the runway 11. Three such carriers 27 are shown, but alternatively, transmitter and sensor receiving devices mounted in a common housing 13, 14 may be disposed to run along the side of the runway 11 on a single carrier 27. In the embodiment shown, the carrier bar 26 is dimensioned to span the width of the runway 11 , and is supported at each end by a support including a floating mechanism mounted on wheels 28. The wheels 28 are mounted within a monorail 29 embedded in the ground just beyond the shoulders of the runway 11 proper to extend parallel therewith. Instead of a monorail 29, the carrier wheels 28 may run on a pair of rails similar to railway tracks, which are embedded similarly, so as not to constitute an obstacle in their own right. Both supports are powered equally, so as to propel the carrier 27 with the carrier bar 26 at substantially 90° to the runway 11's sides. Alternatively, the wheels 28 may be designed to run independently of rails, but to run along the ground itself, and to be controlled in a way to keep the carrier bar 26 at 90° to the side of runway 11. The wheels 28 are rugged enough to allow the carriers 27 to travel smoothly along the undulations of the ground at each side of the runway 11. As a further alternative, the carrier bar 26 may be mounted at the front of a vehicle 34 providing the motive power means. In this case, the carrier bar 26 is preferably mounted on the vehicle 34 to extend substantially equally to either side thereof. The vehicle 34 may be manned or unmanned, if unmanned, controlled remotely to travel up the centre of the runway

11.

In the event of a housing 13, 14 breaking down, because of the failure of its transmitter device 13 or sensor 14, problems with transmission of its output signal 19, damage caused by collision with either aircraft 12 or ground vehicles, or due to any other malfunction, the area 16 of runway surface being scanned by that sensor 14 can alternatively be checked by monitoring the output of its neighbouring sensor 14. Spare housings 13, 14 may be stocked by the airport, making the replacement of defective or damaged housings 13, 14 a simple matter of plugging in a replacement, an operation that could be carried out by a sufficiently knowledgeable member of staff.

If using a carrier bar 26, the width of the carrier bar 26 may require the additional support of bogey wheels at various positions along its width, according to the actual specified width of the carrier bar 26, and the particular means of motive power adopted.

The runway 11 may be swept by a single carrier bar 26, running along its entire length. The carrier bar 26 can travel from one end A of the runway 11 to the other B on a pass and in the reverse direction on the next pass and so on. The carrier 27 may be controlled to run to a position at the extreme end of the runway 11 , where it poses little physical obstruction to the safe passage of aircraft 12 using the runway 11. Alternatively it can be designed to swing into a recessed pit 30, dug for the purpose at each end of the runway 11 , whereby it poses even less of a threat to the safe passage of aircraft 12. Alternatively, as shown in Fig. 2, a series of carriers 27 spaced along the runway 11 , running in conjunction with one another, can sweep the runway 11 , sector by sector. In this case, wherein some of the carriers 27 finish each sweep within the length of the runway 11 , the carrier bars 26 then pivot across the runway 11 , hinging on one of their respective carrier supports, and then retract into recesses 30 provided for the purpose in the ground to the side of the runway 11. In this way they do not present any obstacle to the safe passage of aircraft 12 using the runway 11. These pits 30 are situated parallel with the side of the runway 11. Once the operator has deemed it safe to do so, on command the carrier bars 26 move out of their recesses 30 and pivot across to their respective supports on the other side of the runway 11 in order to begin the next sweep. The number of such carriers 27 so fitted will depend on the length of runway 11. The advantage with multiple carriers 27 is that the system 25 will scan large areas of runway 11 simultaneously, so reducing the time taken for each scan. Also, such a system 25 is modular, and so readily adaptable to the various lengths of airport runways 11 or other carriageways around the world. In this case, as in the case of the single carrier bar 26, each carrier 27 may travel in one pass from A to B, and on the next from B to A, and so on. A combination of transmitters/sensors 13, 14 on carriers 27 and fixed transmitters/sensors 13', 14' may be provided if desired for added certainty of debris 17 detection.

The sensors 14, as built into the housings 13, 14 or the carrier bar(s) 26, are designed for the examination of the surface of the carriageway 11. The housings 13, 14 contain a combination of lase^ sonar, radar and/or optical sensors 14, and possibly other types of sensors 14 as may be required, so as to be able to give all of the necessary information as to any debris 17 present on the carriageway 11 that might constitute a potential threat to an aircraft 12, and also information as to the surface state of the carriageway 11. The sensors 14 are able to scan carriageways 11 of a variety of vertical or horizontal profiles, cross-fall, high centre point, and so on, or any other type of carriageway 11 profile. If mounted on a carrier bar 26, they operate within suitable tolerances, so as to prevent slight variations in the height at which they are travelling above the surface of the carriageway 11 causing inaccuracy in their readings. The sensors 14 are positioned or are moved on each pass so as to be able to cover every part of the carriageway 11 surface. '

The information from the sensors 14 is transmitted to the indicating device 20, 23 at a remote location via a networking system comprising of a series of connections 34 by which data is transmitted to the indicating device 20, 23, incorporating a computing device 20. This computing device 20 directly processes and analyses the received data 19 using a bespoke software package. The systems 10, 25 comprise a single, 20, 21 or duplex 20, 21 and 31 hardware configuration (Fig. 2) in which each computer may be programmed to carry out specific functions. The displayed data gives information as to the grid location, size and nature of foreign object 17, and/or runway surface state, and any other information as required regarding the existence of debris 17 or the surface-state of the carriageway 11. In addition, the computers 20, 21 , 31 may be programmed to display a real-time log of events to facilitate identification of the source of any object 17 found, and data as to the response time of the operator to a given incidence of detected foreign object debris 17.

The member of staff monitoring the inspection system 20, 23 is tasked with taking any action precipitated by information received by the sensors 14 regarding debris 17, and/or passing any information about the surface state to other relevant individuals, pilots, other ground staff etc. If using one or more moving carriers 27, the operative tasked with monitoring the output of the sensor(s) 14 may also control the carrier(s) 27, initiating each run of one or all of the carriers) 27, A to B or B to A, or as the case may be.

Information will be transmitted as to the nature of any debris 17, and, via a grid reference 22 based on the position of a sensor 14 and the distance of the detected object 17 from the sensor 14 or similar, to its precise location on the carriageway 11 surface. The systems 10, 25 comprise a bespoke software package which causes an alarm 32 to be sounded and/or visually indicated to alert the operator to the presence of debris 17 or some other threat on the carriageway 11 surface. The information is tailored to allow the operator to make an informed decision as to the threat to aircraft 12, if any, posed by any debris 17 identified, and to take appropriate action accordingly. Transmission of pictures from cameras 24 (Fig. 1), video or infra red images, or other information, may also be used to assist in making this decision.

In addition, surface-state is also monitored, dry, damp, wet, standing water, other emerging weather conditions etc. In addition, cracks or other developing problems with the tarmac or other carriageway 11 surface is monitored. The system 10, 25 may be programmed to display a real-time log of events to facilitate identification of the source of any object 17 found, and data as to the response time of the operator to a given incidence of detected foreign object debris 17. The operator may work in conjunction with air traffic control and/or control tower staff, in order that any emergency action precipitated by the results of information output by the sensors 14 can be co-ordinated safely, as required by the airport authorities. In addition, the system 10, 25 allows the position of ground staff to be monitored accurately, and includes communication means for them to be directed toward detected foreign object debris 17, for example by the transmission of such data to individual hand-held laptop computer or PDA.

The installation of the inspection system 10 of this invention, utilising the frangible or retractable housings 13, 14 placed at the side(s) of the carriageway 11, provides for inspection 24 hours per day, 365 days per year. The inspection systems 10, 25 allow extremely accurate scanning of the carriageway 11 in substantially all weather conditions, including fog, mist and cloud, conditions which would normally make a visual check difficult or impossible to carry out with any degree of precision. With fixed housings 13, 14, or with a carrier 27 travelling at the side of the carriageway 11, the inspection of the carriageway 11 may be performed continuously. If using the carrier bar(s) 26, the sweep of the carriageway 11 can take place at very high speed, so as to minimise any potential delay in use of a runway 11 or taxiway by aircraft 12. It may be possible to inspect the runway 11 or taxiway with the carrier bar(s) 26 after every take-off and landing cycle. In practice, if using the carrier bar 26, some airports may prefer to inspect the runway 11 or taxiway perhaps only once every 10 or

15 cycles, due to the demands of high volumes of air traffic, and because of any small potential delay caused by each inspection.

The inspection systems 10, 25 of the invention can enhance the existing operational protocols, visual inspections etc. of the airport authorities. In consequence, it is anticipated that the system will become essential equipment for every airport in the world used by major airlines. The systems 10, 25 also give general information as to the state of carriageway 11 , to enhance, or possibly eventually to supersede, existing visual surface-state inspections.

Claims

1. An inspection system (10) for monitoring a carriageway (11), characterised by a transmitter device (13) and a sensor (14) disposed relative to each other in use such that a scanning signal (15) transmitted from the transmitting device (13) scans a predetermined area (16) of the carriageway (11) and is received by the sensor (14), and an indicating device (20, 23) operative in response to an output signal (19) from the sensor (14) to indicate an irregularity in the scanning signal (15) received by the sensor (14).

2. An inspection system according to claim 1 , characterised in that the inspection system (10) is a continuous system.

3. An inspection system according to claim 1 or claim 2, characterised in that the transmitter device (13) transmits a laser scanning signal (15).

4. An inspection system according to claim 3, characterised in that the transmitter device (13) transmits a laser signal (15) at frequencies outside the visible light spectrum.

5. An inspection system according to claim 4, characterised in that the transmitter device (13) transmits a signal (15) at infra-red frequencies.

6. An inspection system according to claim 4 or claim 5, characterised in that the transmitter device (13) transmits a signal (15) at ultra violet frequencies.

7. An inspection system according to claim 1 or claim 2, characterised in that the transmitter device (13) transmits a sonar scanning signal (15).

8. An inspection system according to claim 1 or claim 2, characterised in that the transmitter device (13) transmits a radar scanning signal (15).

9. An inspection system according to any one of claims 1 to 8, characterised in that the transmitter device (13) transmits an optical scanning signal (15).

10. An inspection system according to any one of claims 1 to 9, characterised by a housing (13) in which the transmitter device (13) is mounted.

11. An inspection system according to claim 10, characterised in that the sensor (14) is mounted in the housing (13, 14).

12. An inspection system according to claim 10, characterised in that the transmitter device (13) is mounted in a transmitter housing (13) and the sensor (14) is mounted in a sensor housing (14) spaced from the transmitter housing (13).

13. An inspection system according to claim 12, characterised in that the transmitter housing (13) and the sensor housing (14) are disposed on opposed sides of the carriageway (11).

14. An inspection system according to any one of claims 10 to 13, characterised in that each housing (13, 14) is frangible.

15. An inspection system according to claim 14, characterised in that each housing (13, 14) is of concrete/ cement.

16. An inspection system according to any one of claims 10 to 13, characterised in that each housing (13, 14) is mounted on the ground so as to be retractable on impact.

17. An inspection system according to any one of claims 10 to 13, characterised in that each housing (13, 14) is partially within the ground and partially exposed above ground.

18. An inspection system according to any one of claims 10 to 17, characterised in that each housing (13, 14) is up to 100 cm in height.

19. An inspection system according to any one of claims 10 to 18, characterised in that each housing (13, 14) is movable about theodolite-controlled axes.

20. An inspection system according to any one of claims 1 to 19, characterised by a plurality of transmitter devices (13) and respective sensors (14), in spaced disposition along the carriageway (11).

21. An inspection system according to claim 20, characterised in that the transmitter devices (13) arid respective sensors (14) are disposed along one side of the carriageway (14).

22. An inspection system according to claim 20, characterised in that the transmitter devices (13) and respective sensors (14) are disposed along both sides of the carriageway (11).

23. An inspection system according to any one of claims 20 to 22, characterised in that the housings (13, 14) are disposed to monitor the entire area of the carriageway (11).

24. An inspection system according to any one of claims 20 to 22, characterised in that the housings (13, 14) are disposed to monitor a predetermined portion (16) of the carriageway (11).

25. An inspection system according to any one of claims 20 to 24, characterised in that the housings (13, 14) are disposed whereby the predetermined area (16) scanned by each housing (13, 14) overlaps that of an adjacent housing (13, 14).

26. An inspection system according to any one of claims 20 to 25, characterised in that the plurality of sensors (14) is connected to at least one common indicating device (20, 23).

27. An inspection system according to claim 26, characterised in that the or each indicating device (20, 23) is adapted to indicate the output signal (19) from each of the sensors (14) in succession.

28. An inspection system according to claim 26 or claim 27, characterised in that the or each indicating device (20, 23) is programmable to cycle through a display of a plurality of items of debris (17) and/or surface defects in sequence.

29. An inspection system according to any one of claims 1 to 28, characterised by a calibration target object (37), whereby the sensor (13) is adapted to produce a calibration signal (19) when the scanning signal (15) impinges on the target object (37), the indicating device (20, 23) being operative in response to the calibration signal (19) to indicate the location of the target object (37) for calibration of the system (10).

30. An inspection system according to any one of claims 1 to 29, characterised in that the positioning of an object (17, 37) is determined using a Global Positioning System (GPS).

31. An inspection system according to claim 30, characterised in that the positioning of an object (17, 37) is determined using Differential Global Positioning System (DGPS).

32. An inspection system according to any one of claims 20 to 31 , characterised in that the housings (13, 14) are of a modular design.

33. An inspection system according to any one of claims 1 to 11 , characterised in that the transmitting device (13) and the sensor (14) are mounted on a carrier (27) adapted to traverse substantially the length of the carriageway (11).

34. An inspection system according to claim 33, characterised in that the carrier (27) comprises at least one floating mechanism supporting the transmitting device (13) and the sensor (14).

35. An inspection system according to claim 33, characterised in that the carrier (27) comprises a carrier bar (26) dimensioned substantially to span the width of the carriageway (11).

36. An inspection system according to claim 35, characterised in that the carrier bar (26) is supported at each end by a support.

37. An inspection system according to claim 36, characterised in that each support comprises a floating mechanism supporting the carrier bar (26).

38. An inspection system according to claim 36 or claim 37, characterised in that the carrier (27) comprises motive power means for its propulsion.

39. An inspection system according to claim 38, characterised in that both supports are equally powered, to propel the carrier bar (26) at substantially 90° to the sides of the carriageway (11).

40. An inspection system according to any one of claims 33 to 39, characterised in that the carrier (27) comprises wheels (28) operable to travel along a side of the carriageway (11).

41. An inspection system according to claim 40, characterised in that the wheels (28) are mounted to a monorail (29).

42. An inspection system according to claim 41, characterised in that the monorail track (29) is buried beneath the surface of the ground.

43. An inspection system according to claim 41 or claim 42, characterised in that a monorail track (29) is disposed along each side of the carriageway (11).

44. An inspection system according to claim 40, characterised in that the wheels (28) are designed to run along the ground itself independently of rails, and the carrier (27) is controlled to run parallel with the side of the carriageway (11).

45. An inspection system according to any one of claims 33 to 44, characterised in that the earner (27) is controlled to run between positions substantially at the ends of the carriageway (11).

46. An inspection system according to any one of claims 33 to 44, characterised in that a plurality of carriers (27), spaced longitudinally of the carriageway (11) and running in conjunction with one another, are provided to sweep the carriageway (11), sector by sector.

47. An inspection system according to claim 46, characterised in that each carrier (27) comprises a carrier bar (26), the carrier bar (26) is hinged on one of the supports and is pivotable across the carriageway (11) to extend parallel therewith.

48. An inspection system according to claim 47, characterised in that each carrier bar (26) may then slide into a recess (30) provided for the purpose in the ground to the side of the carriageway (11).

49. An inspection system according to claim 48, characterised in that a recess (30) is disposed to extend parallel with the side of the carriageway (11).

50. An inspection system according to claim 35, characterised in that the carrier bar (26) is mounted at the front of a vehicle (34) providing the motive power means.

51. An inspection system according to claim 50, characterised in that the carrier bar (26) is mounted on the vehicle (34) to extend substantially equally to either side thereof.

52. An inspection system according to claim 50 or claim 51, characterised in that the vehicle (34) is a manned vehicle.

53. An inspection system according to claim 50 or claim 51, characterised in that the vehicle (34) is an unmanned vehicle.

54. An inspection system according to claim 53, characterised in that the vehicle (34) is controlled remotely to travel along the centre of the carriageway (11).

55. An inspection system according to any one of claims 1 to 54, characterised in that the or each indicating device (20, 23) is disposed at a location remote from the or each sensor (14).

56. An inspection system according to claim 55, characterised in that the or each indicating device (20, 23) comprises a computing device (20).

57. An inspection system according to claim 56, characterised in that the output signal (19) from the or each sensor (14) is transmitted to the remote location via a networking system comprising a series of connections (34) by which data is be transmitted to the or each computing device (20).

58. An inspection system according to claim 56 or claim 57, characterised in that the or each computing device (20) comprises a single hardware configuration.

59. An inspection system according to claim 56 or claim 57, characterised in that the or each computing device (20) comprises a duplex hardware configuration (31).

60. An inspection system according to any one of claims 1 to 59, characterised in that the or each indicating device (20, 23) gives zero indication unless an output signal (19) from a sensor (14) indicates an irregularity in the scanning signal (15) received by the sensor (14).

61. An inspection system according to any one of claims 1 to 60, characterised in that the or each indicating device (20, 23) comprises an alarm (32) operable on receiving an output signal (19) indicating an irregularity in the scanning signal (15) received by a sensor (14).

62. An inspection system according to claim 61, characterised in that the alarm (32) provides an audible signal.

63. An inspection system according to claim 61 or claim 62, characterised in that the alarm (32) provides a visual signal.

64. An inspection system according to any one of claims 1 to 63, characterised by a camera (24) to provide images of an irregularity detected by a sensor (14).

65. An inspection system according to claim 64, characterised in that the camera (24) is mounted on a tower (33) disposed spaced from the carriageway (1 i ,

66. An inspection system according to claim 64 or claim 65, characterised in that the or each indicating device (20, 23) provides a graphic image corresponding with the irregularity.

67. An inspection system according to claim 64 or claim 65, characterised in that the or each indicating device (20, 23) provides a photographic image corresponding with the irregularity.

68. An inspection system according to any one of claims 64 to 67, characterised in that the or each indicating device (20, 23) provides a video image corresponding with the irregularity.

69. An inspection system according to any one of claims 55 to 68, characterised in that the or each indicating device (20, 23) provides an infra red image corresponding with the irregularity.

70. An inspection system according to any one of claims 55 to 68, characterised in that the or each indicating device (20, 23) provides a thermal image corresponding with the irregularity.

71. An inspection system according to any one of claims 1 to 70, characterised by a bird- scaring device (35) activated when the signal (15) received by a sensor (14) has a temporary irregularity.

72. An inspection system according to any one of claims 1 to 71, characterised by a temperature sensing device (36) operable to sense the temperature of the surface of the carriageway (11) or air adjacent thereto and transmit a signal dependent on the sensed temperature to the indicating device (20, 23).

73. An inspection system according to any one of claims 1 to 72, characterised in that the indicating device (20, 23) is programmed to display a real-time log of events to facilitate identification of the source of any object (17) found.

74. An inspection system according to any one of claims 1 to 73, characterised in that the indicating device (20, 23) is programmed to display data as to the response time of an operator to a given incidence of detected object (17).

75. An inspection system according to any one of claims 1 to 74, characterised by communication means whereby a person may be directed to an object (17) that has been detected.

76. An inspection system according to any one of claims 1 to 75, characterised by a cut-off device operable when the inspection system detects a predetermined moving object (12, 34) in the predetermined area (16) of the carriageway (11).

77. An inspection system according to any one of claims 1 to 76 in combination with an SMR system.

78. An inspection system according to claim 77, characterised by a cut-off device operable when the SMR system detects a predetermined moving object (12, 34) in the predetermined area (16) of the carriageway (11).

79. An inspection system according to any one of claims 76 to 78, characterised in that a predetermined moving object (12, 34) has means for disabling the system (10, 25) during such movement.

80. An inspection system (20, 23) for monitoring a carriageway (11) substantially as hereinbefore described with reference to and as illustrated in Fig. 1 or Fig. 2 of the accompanying drawings.