CA2016088A1 - Monitoring apparatus - Google Patents
Monitoring apparatusInfo
- Publication number
- CA2016088A1 CA2016088A1 CA 2016088 CA2016088A CA2016088A1 CA 2016088 A1 CA2016088 A1 CA 2016088A1 CA 2016088 CA2016088 CA 2016088 CA 2016088 A CA2016088 A CA 2016088A CA 2016088 A1 CA2016088 A1 CA 2016088A1
- Authority
- CA
- Canada
- Prior art keywords
- camera
- incident
- images
- image memory
- controller
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/16—Anti-collision systems
- G08G1/164—Centralised systems, e.g. external to vehicles
-
- G—PHYSICS
- G08—SIGNALLING
- G08G—TRAFFIC CONTROL SYSTEMS
- G08G1/00—Traffic control systems for road vehicles
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/04—Detecting movement of traffic to be counted or controlled using optical or ultrasonic detectors
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Traffic Control Systems (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Monitoring apparatus for monitoring traffic flow in a tunnel, comprising a plurality of cameras each connected to a camera controller. Each camera controller includes an image memory for periodically storing still images from the camera associated therewith. A plurality of incident detectors are associated with each camera. The incident detectors detest the passage of vehicles and determine whether or not a traffic incident, eg congestion or an accident, has occurred in accordance with an algorithm. When an incident has occurred an incident detection signal is generated which is communicated to the camera controllers. The image memory of the relevant camera controller is responsive to the detection signal to identify and freeze a plurality of images prior to the incident which are then passed to the central controller, so that the circumstances leading up to the incident can be reviewed.
Figure 2
Monitoring apparatus for monitoring traffic flow in a tunnel, comprising a plurality of cameras each connected to a camera controller. Each camera controller includes an image memory for periodically storing still images from the camera associated therewith. A plurality of incident detectors are associated with each camera. The incident detectors detest the passage of vehicles and determine whether or not a traffic incident, eg congestion or an accident, has occurred in accordance with an algorithm. When an incident has occurred an incident detection signal is generated which is communicated to the camera controllers. The image memory of the relevant camera controller is responsive to the detection signal to identify and freeze a plurality of images prior to the incident which are then passed to the central controller, so that the circumstances leading up to the incident can be reviewed.
Figure 2
Description
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Title: MONITORING APPAR~TUS
Back~round of the invention:
This invention relates to monitoring apparatus, particularly, but not exclusively for monitoring traffic flow in a tunnel.
Monitoring apparatus for intruder detection i8 known, for example that manufactured by the Vision Research Company Limited under the trade name Pixstore 256. Such apparatus generally comprises a video camera connected to a monitor screen via a control unit which is further connected to an intruder detection device eg an infra red, micro wave, ultrasonic or perimeter type device, the control unit actuating an alarm and freezing the image from the video camera at the instant of detection thus allowing a 'snap shotl picture of the intrus$on.
It i8 a d$sadvantage of such a system that it i~ only capable of responding to and recording an incident at the time the incident occurs and is thus unsuitable for providing information as to how the $ncident arose. The system is thus unsu$table for mon$toring traffic related incidents.
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SummarY of the invention According to the invention in a first aspect, there is provided monitoring apparatus comprising a camera, an image memory for storing images from the camera, an incident detector for generating an incident detection signal when an incident occurs, the image memory being responsive to the detection signal whereby a plurality of said images prior to the incident are identified; and means for reviewing said prior images Preferably, the monitoring apparatus is used for detecting a traffic incident, preferably in a tunnel, the camera being a video camera providing images to a ~ -camera controller which stores the images periodically in an image memory The incident detector preferably `
comprises a road sensor, for sensing when a vehicle passes in the field of view of the camera and a proces~or for determining the occupancy of the road and, , ; from this information, if an incident has occurred, the inol~d-nt d-t-ctor then gen-rating the incident detection ignal ';Other preferred features of the invention are mentioned in dependent Claims 2 to 20 ~` It is a further disadvantage of the prior art apparatus that the control unie is disposed at a central onitoring location, ~ervicing a plurality of video , .
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Title: MONITORING APPAR~TUS
Back~round of the invention:
This invention relates to monitoring apparatus, particularly, but not exclusively for monitoring traffic flow in a tunnel.
Monitoring apparatus for intruder detection i8 known, for example that manufactured by the Vision Research Company Limited under the trade name Pixstore 256. Such apparatus generally comprises a video camera connected to a monitor screen via a control unit which is further connected to an intruder detection device eg an infra red, micro wave, ultrasonic or perimeter type device, the control unit actuating an alarm and freezing the image from the video camera at the instant of detection thus allowing a 'snap shotl picture of the intrus$on.
It i8 a d$sadvantage of such a system that it i~ only capable of responding to and recording an incident at the time the incident occurs and is thus unsuitable for providing information as to how the $ncident arose. The system is thus unsu$table for mon$toring traffic related incidents.
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SummarY of the invention According to the invention in a first aspect, there is provided monitoring apparatus comprising a camera, an image memory for storing images from the camera, an incident detector for generating an incident detection signal when an incident occurs, the image memory being responsive to the detection signal whereby a plurality of said images prior to the incident are identified; and means for reviewing said prior images Preferably, the monitoring apparatus is used for detecting a traffic incident, preferably in a tunnel, the camera being a video camera providing images to a ~ -camera controller which stores the images periodically in an image memory The incident detector preferably `
comprises a road sensor, for sensing when a vehicle passes in the field of view of the camera and a proces~or for determining the occupancy of the road and, , ; from this information, if an incident has occurred, the inol~d-nt d-t-ctor then gen-rating the incident detection ignal ';Other preferred features of the invention are mentioned in dependent Claims 2 to 20 ~` It is a further disadvantage of the prior art apparatus that the control unie is disposed at a central onitoring location, ~ervicing a plurality of video , .
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cameras so that malfunction of the unit cau~es the whole monitoring system to be disabled.
According to the invention in a second aspect there is provided monitoring apparatus comprising a plurality of monitoring stations each having a camera and a local camera controller, the camera controller having an image memory for storing images from the camera; and a remote central controller connected to the camera controllers for selectively receiving said stored images.
According to the invention in a third aspect, there is provided a method of determining the existence of a traffic incident comprising the ~teps of measuring the average speed of vehicles passing a sensor in a first time period, measuring the average speed of vehicles passing the sensor in second time period shorter than the first time period, calculating the difference between the average speeds for the two time periods and ~: :
generating an incident detectlon signal when the ~ - difference is above a predetermined threshold.
i: Brief descri~tion of the drawings:
~;~ An embodlment of the lnvention will now be described, by way of example, with reference to the accompanying drawings, in which:
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Fi gure 1 is a 8 chematic diagram 8 howing the di 8 pO8 i tion of camera6 and incident detectors of an embodiment of the invention in one carriage way of a road tunnel ~ '; ''' .. ~
Figure 2 i8 a schematic diagram showing an embodiment of the inventlon Figure 3 i8 a schematic diagram of a camera controller ;~
of the embodlment of Figure 2 Figure 4 is a schematic diagram of the data conversion unit of the embodiment of Figure 2 Figure 5 i~ a schematic diagram of a 6ite controller of `~
the embodiment of Figure 2 Figure 6 is a schematic diagram of a vehicle detection ~: ~
module~ of the embodiment of Figure 2 p-~orl~tlon of the ~referred -mbodiment ; Ref-rring to the flgures, an mbodiment of monitoring apparatus according to the invention is shown :i : ~ ' ~ , . ~.
The monitoring apparatus i8 axranged for use in traffic monltoring, to monitor and detect a traffic incident on a hlghw~y and, specifically, in a road tunnel : .
As shown in Figure 1, a plurality of video cameras 10, ~: \
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12, 14 are attached at spaced intervals to the wall of a tunnel, each camera having a field of view 22, 24, 26 which overlaps with the fiela of view of the preceaing camera. The cameras monitor one carriage way 30 havlng two lanes 32, 34 in the tunnel 20 and each camera 10, 12, 14 has associated therewith a plurality of vehicle sensors 40 - 53 .... of which sensors 40 - 45 are as60ciated with camera 10 and sensors 46 - 51 are associated wlth camera 12. As de~crlbed below, the sensing of an incldent by one or more of the sensors a8~0ciated with the camera will cause the retention of images showing both the incident and the circum6tances leading up to the incident. The sensors in each lane are separated by a distance D whlch is chosen according to condltions and is preferably 60m.
A block diagram of an embodiment of monitoring apparatu6 of the invontion as a whole is shown in Figure 2.
Bach camera 10, 12, is connected to a local camera controller 60, 62, 64 each controller processing image6 received fro~ its respective camera. All camera controllers àre connected to a central controllor 66 remote from the camera sites vla a data bus 70, the central controller having a supervising computer 72, with associated hard disc storage and hard copy facilities, a monitor 74 and a data conversion unit 76 shown in more detall ln Flgure 4 and formed of 8tandard 6 2~
electronic circuits providing D/A and A/D conversion, modulatlon and demodulation and flltering of video signals and instruotions. The unit 76 act~ as an I/0 and processing interface between the computer 72, monitor 74 and camera controllers 60 - 64.
Camera controller 60 is shown in more detail in Figure 3 and includes an A/D converter 80 for converting the analogue video image signal from the video camera 10 to a digital equivalent and providing an output digital signal to a central processing unit 82. The CPU 82 stores frames of the digital video image signal at interval~ in a memory stack 84 typically having capacity for 32 frames with a resolution 192 x 300 pixels x 64 grey levels, implying a memory requirement of approximately 24 K bytes/frame. The interval period may be either constant or variable and is preferably of at least one second duration, 80 that the memory stack provides a record of past events of at least 32 seconds duration.
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The CPU 82 i~ further connected to a data Interface for :
transmitting/receiving signals to/from central ~ ~-controller 66~via bus 70. Each camera controller has a unique address and upon an instruction signal from the central computer 72 tagged w1th the address, can transmit real time video images direct from the video oamera 10 or can transmit all or part of frame store - - -7 2~5Q~3~
84 The camera controllers only transmits on instruction from central computer 66 The CPU 82 is also responsive to an inoident detection signal, from central control 66 on bus 70 or from an incident detector (described below) on data line 88 to freeze the contents of frame memory 84 in the event of an incident being detected, 90 that the contents of the frame store, which records past images prior to the detected incident are retained for transmi 8 9 ion to the central controller 66, thus providing a record of the circumstances leading up to the detected incident Optionally, the CPU can move a frame pointer 80 that some of the frames labelled F are stored and future, post in¢ident images are stored higher up the stack, thus allowing retention of past events and at the same time continued monitoring of current events The frame memory 84 may optionally be formed as a robust detatohable cartridge eg of the type disclosed in co-pending European patent application No 89303333 2, thl- allowing r-moval and retrieval of image data held in the cartridge in the event of ~ystem failure The cartridge may be form-d from physical and thermal shock resistant materials, for example a polycarbonate case having epoxy re~in potting, ~o that retrieval of the cartridge when the camera controller ha~ suffered all or partial de3truction will still be possible Use of a d-tatchable cartridge also allow~ for corroboration, 8 2~
after an incident, between the content of the frame memory and the image data tran~mltted to the central controller 66 ~ -~ , The central controller 66 is further oonnected, via a data bus 90, to a plurality of incident detector6 92, 94, 96 Each incident detector comprises a site controller 100, 102 104 Each site controller has connected thereto three vehiole detection modules (VDM~) 120, 122, 124; 126; 128; 130; each of which contains signal processlng aircuitry for a pair of the vehicle sensors 40, 41 , the pair being connected to -~
the respective VDM Each site controller is further aonnected to an associated one of the camera controllers via signal lines 140, 142, 144 The vehicle detection module 120 is shown in more detail in Figure 6 The road seneor 40 comprises a square four turn inductive loop 200 which is connected to the VDM
120~via an i~olating transformer 210 ~he VDM inaludes an alternating current source 220 having a frequency of approximately 60 kHz and a frequency measuring circuit comprising a programmabl- down counter 230, an elapse ;
counter 240 connected to counter 230 by line 235 and `;
driven by higb pe-d~clock (10 MHz) 250 for measuring the duration of the o~clllation count and a CPU 260 Each sensor 40, 41 ha~ its own alternating current `~
, source 220, the fr-quency m-asuring circuit being :.~-:
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connected to one or other of the sensors by means of switch 270 under control of CPU 260 in a time division manner. Preferably, the CPU 260 switahes between sensors 40, 41 at one millisecond intervals.
In use, the sensor 40 i8 placed in the road lane either attached on the road surface or 3unk into the road surface. The inductance of the loop 200 will drop when a metal bodied vehicle passes over. This in turn will affect the oscillation frequency of the circuit comprising the loop 200 and source 220. The frequency measuring circuit measures this frequency by counting down a selected number of oscillations of the alternating voltage signal; when the counting operation is being performed, a signal on line 235 changes level thus providing a start/stop sign~l to counter 240 which , ~
measures the time duration of the count, this giving the period of the alternating signal and thus its frequency. The count value is passed to CPU 260 via bus 255.
Preferably, the CPU controls the counter to output a start/stop signal on line 235 after a plurality of osclllations (eg 8, 16 or 32) selected by user configurable ~witches 237, to improve resolution accuracy.
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The CPU 260 processe~ the counter information and compares the derived frequency measurement with a threshold, producing a true/false slgnal indicating presence adjacent the loop 40 of a vehicle. The signal is sent to the site controller 100 on bus 265.
The site controller 120 i 8 shown in more detail in Figure S and i8 of stand alone construction, based on the MARRSMAN 600 traffic management controller manufactured by the applicants. The site controller 120 has a I/O circuit 300 which received frequency information signals on buses 265 - 267 from respective :
VDMs 120, 122, 124. The I/O circuit also provides an - output on bus 140 to camera controller 60.
The I/O circuit and all other functions of the site controller are controlled by a CPU 310 to which is further connected a keyboard/display 315, to allow on 1te initiali~atlon and input/output of data from the site controllerj a data cartridge 320 and interface 325 : :~
preferab}y of a type dlsolosed ln European patent application No 89303333.2, for storlng incldent and oooupancy data, a ROM/RAM 355 for storing CPU programmes and operational data and a network interface 330 whlch provldes a oommunlcations link with data bus 90.
The network interface 330 includes a processor 335 and two port universal asyncronous receiver transmitter ~:
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(UART) 340 for data transfer. A switched bypass bus 350 having a plurality of electromechanical relays i8 further provided, the relays being blased closed but held open by the site controller CPU 310. The bus 350 acts to 'short circuit~ the network lnterface 330 in the event of power failure of the site controller 120 or when the site controller cannot make sense of signals being transmitted through UART 340, 80 that failure of one site controller w1ll not affect the operation of others connected to data bus 90 downstream of the failed site controller.
The CPU has random access and read only memories 355 for internal data storage and for storing contrsl and incident identification programmes. The site controller 120 is connected to a power supply and also has a local ;~ backup supply in the form of a rechargable battery (not shown) for use ln the event of a general power fallure.
~In u~e, the site controller receives the vehlcle presenae lnformatlon from the VDMs 120, 122, 124 and from thls calculates the degree of ~occupancy~ and ''density' of any one sensor by vehicles. Occupancy is defined as the number of consecutlve seconds that a `::
vehicle has been sensed as present by the sensor.
Density is defined as the percentage time in a given time interval that the loop has sensed the presence of a ,'-.: ':: .' --, ::' ~6~
vehicle or vehicles This information is then used to oalculate if a traffic incident has ocaurred in accordance with an algorithm Such algorithms are ~nown to those skilled in the art, as exemplified by ths high occupancy (HIOCC) algorithm developed by the Transport and Road Research Laboratory (T~RL) as disclosed in TRRL
supplementary reports Nos 775 (Automatic incident detection, experience with two TRRL algorithm HIOCC; J F
Collins 1983) and 526 (Automatic inoident deteotion -TRRL algorithms HIOCC and PATREG; J F Collins, C M
Hopkins and J A Martin 1979) The HIOCC algorithm as disclosed in the above documents, the contents of which are incorporated herein by reference, operates by detecting stationary or slow moving vehicles to indicate a traffic queue caused by an incident or by congestion It looks for several ~ -oonsecutive seconds of high detector occupancy to detect queues and ino1dents in high traffio flows A programme ~
in acoordance with the flow diagram of Figure 3 of ~ ;
r-port 526 is stored in ROM in site oontroller 120 and -~ `
CPU 310 processes the oooupancy data from VDMs 120 - 124 in acoordance with the programmed algorithm The resultant occupancy, denslty and incident data is stored locally in data cartridge 320 and is also sent to the central oontroller 66 via data bus 90 When the algorlthm detects a trafflc lncident, an incident detection signal i8 sent both to the central controller and to the camera controller 60 associated with the site controller 100. The incident detection signal causes the oamera controller to freeze a predetermined number of image~ in the frame store 84 as previously descrlbed, thus provlding a stored record of the circumstances leading up to the incldent as detected by the incident detector.
In addition to the HIOCC algorithm, the site controller uses a speed (as opposed to occupancy) based algorithm using two ad~acent loop sensors eg 41, 43 in any one lane. Such an algorlthm provides additional information concerning slow moving vehicles - whi¢h are, in themselves, a traffic hazard. Furthermore, by basing analysi~ on speed, speeding violations may also be :: ~
detected.
An example of a suitable algorithm is as follows:
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Two measurement intervals Tl and T2 (between one minute i ' and twenty fqur hours depending on occupancy) are chosen, interval Tl representing a relatively longer perlod than T2. Uslng ~djacent loop detectors 41, 43 the average speed in each interval Tl, T2 is calculated and updated as each vehicle passes, givlng average speeds S1, S2. The difference between these speeds (Sl ., . . . . ~ . .
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-S2) glves an indication of short term speed variation away from the long term average and if over a predetermined threshold SD gives an indication of an incident. Furthermore, if S1 or S2 or the instantaneous vehicle speed fall outside predetermined high or low speed thresholds THH, THL, this also gives an indication of a probable incident. Examples of suitable parameters are T1 = 1 hour, T2 = 6 minutes, SD = 5 kph, THH = 200 ~ kph, THL ~ 20 kph.
;~ - , The site controllers 100, 102, 104 form nodes of a local area network (LAN) having a standard format and operating protocols, each node passing messages along ~ -the data bus 90. Each controller has a unique network identifier, with identifiers being reserved for ~all stat~ons~ called and the central control 66.
h~- topology of the networX is a daisy chain with out go1ng~message~ being passed to the end of the line and naomlng~messages belng passed back to the central controller 66. Each site oontroller is responsible for passing messagès along the line when a character arrives i~ it is bufered until the whole message is complcte. It is then retransmitted.
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A1l s1t- controllers examine me6~ages, discard corrupt ~;
m-ssage~, accept tho~e w1th matching addresses and pass on others.
When a site controller has a message of its own for the central controller 66, it tests the status of the incoming line from the previous site controller. If the line is busy, the site controller will continue to re-tranmsit data from the previous site controller until the line is clean, at whlch point the site controller will aommence transmission of its own message. During thi~ tlme any incoming me~ages from the outlying site controllers will be buffered in the 6ite controller UART
for re-transmission at the earliest opportunity.
Site controllers are assigned unique addresses and all , messages from site controllers to the central controller 66 are tagged with this address. Messages from the central controller to slte controllers are either 'all ~"
-~ ~ stations' to all site controllers or 'addressed' to ~: .
individual site controller8.
Me-8ageo are transmitted along the LAN as the data field of a network packet, packets having the following format:
i~` ' 1. Packet header 2. Destination address 3. Source address 4. Control flag :`
A: Acknowledgement B: Text mes~age `:`l`' 16 2~ 6Q~3 C: Incident detection/alarm mes~age D: Status message 5. Field check sum 6. Data box size 7. Data block The packet receiving protocol for each site controller is as follows:
1. Each complete message is re-transmitted along the line.
2. Incoming characters are also placed into the incoming message buffer.
3. When a full packet is received the unit compares the destination address with its own node id. -~ -~
4. If the id and address do not match no further action is taken.
5.~ If the id and address match then the packet iB
interpreted, involving the following:
A. The oh-cks ar- miscalculated ~ -` B. If the cheok sum is incorrect a bad packet error is flagged C. Th- response to a bad packet error is to do nothing and allow the souroe to time out and resend D. If the checks are incorrect, the data block is passed to the CPU for action and an acknowledgement ~, ~ (ACR) packet is sent to the central controller.
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The packet sending protocol of the site controllers is as follows:
1. The messages are formatted by the site controller CPU into a p~cket having the form noted above.
2. The packet is placed in an outgoing packet queue and the count of re-tries set to zero.
3. The packet is transmitted.
4. If an ACX packet i8 received from the target node/central controller with the correct packet ID then the packet has been successfully transmitted and is removed from the queue.
If no reply is received before a predetermined time out then the packet is re-sent and the count of retries for this packet is incremented.
If the count of time out re-tries reaches the user opecified maximum then a message time out error is flagged.
During normal operation when no incident detections are present the central controller 66 will poll the status of each site controller by sending a request for a status packet. In reply to the status request the units will respond with a data packet giving the following parameters:
1. Occupancy (the number of consecutive seconds for which a sensor has been found to be occupied).
2. Density: the percentage of tlme at a given lnterval for which the loop has been occupied.
3. Incident detection status.
4. Loop status.
S. Mislcellaneous.
When an inaident detection signal is generated, the sensing unit sends an incident detection packet to the central controller 66. The central controller 66 ~: ;
acknow~edges receipt of the pa¢ket (otherwise the packet is re-sent). The central controller then acts to freeze the memory store for the relevant camera/camera controller. In parallel, an incident detection signal i8 sent direct from the site controller to its associated ¢amera controller.
While the embodiment of the invention as described above ha~be-n appli-d to a road traffic sensing sy8tem, this not~to be~construed as limltative. For example, the ~ ~:
invention may be used in a driver's cab of a train, the incident detector being respon8ive to an automatic warnIng system (AW6) 'line ocoupied' signal showing, for xample, wh-n a train has gone through a danger signal.
Alternatively, the lnoident detector could be a sensor aonnected to the front buffers 0f the train 80 that data 18 stored on impact w1th another vehicle or ob~ect on 19 ~6C~
the track. In suah cir¢um~tances, the data cartrldge could be made to 'black box' ~tandards.
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cameras so that malfunction of the unit cau~es the whole monitoring system to be disabled.
According to the invention in a second aspect there is provided monitoring apparatus comprising a plurality of monitoring stations each having a camera and a local camera controller, the camera controller having an image memory for storing images from the camera; and a remote central controller connected to the camera controllers for selectively receiving said stored images.
According to the invention in a third aspect, there is provided a method of determining the existence of a traffic incident comprising the ~teps of measuring the average speed of vehicles passing a sensor in a first time period, measuring the average speed of vehicles passing the sensor in second time period shorter than the first time period, calculating the difference between the average speeds for the two time periods and ~: :
generating an incident detectlon signal when the ~ - difference is above a predetermined threshold.
i: Brief descri~tion of the drawings:
~;~ An embodlment of the lnvention will now be described, by way of example, with reference to the accompanying drawings, in which:
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Fi gure 1 is a 8 chematic diagram 8 howing the di 8 pO8 i tion of camera6 and incident detectors of an embodiment of the invention in one carriage way of a road tunnel ~ '; ''' .. ~
Figure 2 i8 a schematic diagram showing an embodiment of the inventlon Figure 3 i8 a schematic diagram of a camera controller ;~
of the embodlment of Figure 2 Figure 4 is a schematic diagram of the data conversion unit of the embodiment of Figure 2 Figure 5 i~ a schematic diagram of a 6ite controller of `~
the embodiment of Figure 2 Figure 6 is a schematic diagram of a vehicle detection ~: ~
module~ of the embodiment of Figure 2 p-~orl~tlon of the ~referred -mbodiment ; Ref-rring to the flgures, an mbodiment of monitoring apparatus according to the invention is shown :i : ~ ' ~ , . ~.
The monitoring apparatus i8 axranged for use in traffic monltoring, to monitor and detect a traffic incident on a hlghw~y and, specifically, in a road tunnel : .
As shown in Figure 1, a plurality of video cameras 10, ~: \
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12, 14 are attached at spaced intervals to the wall of a tunnel, each camera having a field of view 22, 24, 26 which overlaps with the fiela of view of the preceaing camera. The cameras monitor one carriage way 30 havlng two lanes 32, 34 in the tunnel 20 and each camera 10, 12, 14 has associated therewith a plurality of vehicle sensors 40 - 53 .... of which sensors 40 - 45 are as60ciated with camera 10 and sensors 46 - 51 are associated wlth camera 12. As de~crlbed below, the sensing of an incldent by one or more of the sensors a8~0ciated with the camera will cause the retention of images showing both the incident and the circum6tances leading up to the incident. The sensors in each lane are separated by a distance D whlch is chosen according to condltions and is preferably 60m.
A block diagram of an embodiment of monitoring apparatu6 of the invontion as a whole is shown in Figure 2.
Bach camera 10, 12, is connected to a local camera controller 60, 62, 64 each controller processing image6 received fro~ its respective camera. All camera controllers àre connected to a central controllor 66 remote from the camera sites vla a data bus 70, the central controller having a supervising computer 72, with associated hard disc storage and hard copy facilities, a monitor 74 and a data conversion unit 76 shown in more detall ln Flgure 4 and formed of 8tandard 6 2~
electronic circuits providing D/A and A/D conversion, modulatlon and demodulation and flltering of video signals and instruotions. The unit 76 act~ as an I/0 and processing interface between the computer 72, monitor 74 and camera controllers 60 - 64.
Camera controller 60 is shown in more detail in Figure 3 and includes an A/D converter 80 for converting the analogue video image signal from the video camera 10 to a digital equivalent and providing an output digital signal to a central processing unit 82. The CPU 82 stores frames of the digital video image signal at interval~ in a memory stack 84 typically having capacity for 32 frames with a resolution 192 x 300 pixels x 64 grey levels, implying a memory requirement of approximately 24 K bytes/frame. The interval period may be either constant or variable and is preferably of at least one second duration, 80 that the memory stack provides a record of past events of at least 32 seconds duration.
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The CPU 82 i~ further connected to a data Interface for :
transmitting/receiving signals to/from central ~ ~-controller 66~via bus 70. Each camera controller has a unique address and upon an instruction signal from the central computer 72 tagged w1th the address, can transmit real time video images direct from the video oamera 10 or can transmit all or part of frame store - - -7 2~5Q~3~
84 The camera controllers only transmits on instruction from central computer 66 The CPU 82 is also responsive to an inoident detection signal, from central control 66 on bus 70 or from an incident detector (described below) on data line 88 to freeze the contents of frame memory 84 in the event of an incident being detected, 90 that the contents of the frame store, which records past images prior to the detected incident are retained for transmi 8 9 ion to the central controller 66, thus providing a record of the circumstances leading up to the detected incident Optionally, the CPU can move a frame pointer 80 that some of the frames labelled F are stored and future, post in¢ident images are stored higher up the stack, thus allowing retention of past events and at the same time continued monitoring of current events The frame memory 84 may optionally be formed as a robust detatohable cartridge eg of the type disclosed in co-pending European patent application No 89303333 2, thl- allowing r-moval and retrieval of image data held in the cartridge in the event of ~ystem failure The cartridge may be form-d from physical and thermal shock resistant materials, for example a polycarbonate case having epoxy re~in potting, ~o that retrieval of the cartridge when the camera controller ha~ suffered all or partial de3truction will still be possible Use of a d-tatchable cartridge also allow~ for corroboration, 8 2~
after an incident, between the content of the frame memory and the image data tran~mltted to the central controller 66 ~ -~ , The central controller 66 is further oonnected, via a data bus 90, to a plurality of incident detector6 92, 94, 96 Each incident detector comprises a site controller 100, 102 104 Each site controller has connected thereto three vehiole detection modules (VDM~) 120, 122, 124; 126; 128; 130; each of which contains signal processlng aircuitry for a pair of the vehicle sensors 40, 41 , the pair being connected to -~
the respective VDM Each site controller is further aonnected to an associated one of the camera controllers via signal lines 140, 142, 144 The vehicle detection module 120 is shown in more detail in Figure 6 The road seneor 40 comprises a square four turn inductive loop 200 which is connected to the VDM
120~via an i~olating transformer 210 ~he VDM inaludes an alternating current source 220 having a frequency of approximately 60 kHz and a frequency measuring circuit comprising a programmabl- down counter 230, an elapse ;
counter 240 connected to counter 230 by line 235 and `;
driven by higb pe-d~clock (10 MHz) 250 for measuring the duration of the o~clllation count and a CPU 260 Each sensor 40, 41 ha~ its own alternating current `~
, source 220, the fr-quency m-asuring circuit being :.~-:
.
: ;
2~ ~Q~
connected to one or other of the sensors by means of switch 270 under control of CPU 260 in a time division manner. Preferably, the CPU 260 switahes between sensors 40, 41 at one millisecond intervals.
In use, the sensor 40 i8 placed in the road lane either attached on the road surface or 3unk into the road surface. The inductance of the loop 200 will drop when a metal bodied vehicle passes over. This in turn will affect the oscillation frequency of the circuit comprising the loop 200 and source 220. The frequency measuring circuit measures this frequency by counting down a selected number of oscillations of the alternating voltage signal; when the counting operation is being performed, a signal on line 235 changes level thus providing a start/stop sign~l to counter 240 which , ~
measures the time duration of the count, this giving the period of the alternating signal and thus its frequency. The count value is passed to CPU 260 via bus 255.
Preferably, the CPU controls the counter to output a start/stop signal on line 235 after a plurality of osclllations (eg 8, 16 or 32) selected by user configurable ~witches 237, to improve resolution accuracy.
~: .
`?, -~
:
2~
The CPU 260 processe~ the counter information and compares the derived frequency measurement with a threshold, producing a true/false slgnal indicating presence adjacent the loop 40 of a vehicle. The signal is sent to the site controller 100 on bus 265.
The site controller 120 i 8 shown in more detail in Figure S and i8 of stand alone construction, based on the MARRSMAN 600 traffic management controller manufactured by the applicants. The site controller 120 has a I/O circuit 300 which received frequency information signals on buses 265 - 267 from respective :
VDMs 120, 122, 124. The I/O circuit also provides an - output on bus 140 to camera controller 60.
The I/O circuit and all other functions of the site controller are controlled by a CPU 310 to which is further connected a keyboard/display 315, to allow on 1te initiali~atlon and input/output of data from the site controllerj a data cartridge 320 and interface 325 : :~
preferab}y of a type dlsolosed ln European patent application No 89303333.2, for storlng incldent and oooupancy data, a ROM/RAM 355 for storing CPU programmes and operational data and a network interface 330 whlch provldes a oommunlcations link with data bus 90.
The network interface 330 includes a processor 335 and two port universal asyncronous receiver transmitter ~:
.
2~ Q~
(UART) 340 for data transfer. A switched bypass bus 350 having a plurality of electromechanical relays i8 further provided, the relays being blased closed but held open by the site controller CPU 310. The bus 350 acts to 'short circuit~ the network lnterface 330 in the event of power failure of the site controller 120 or when the site controller cannot make sense of signals being transmitted through UART 340, 80 that failure of one site controller w1ll not affect the operation of others connected to data bus 90 downstream of the failed site controller.
The CPU has random access and read only memories 355 for internal data storage and for storing contrsl and incident identification programmes. The site controller 120 is connected to a power supply and also has a local ;~ backup supply in the form of a rechargable battery (not shown) for use ln the event of a general power fallure.
~In u~e, the site controller receives the vehlcle presenae lnformatlon from the VDMs 120, 122, 124 and from thls calculates the degree of ~occupancy~ and ''density' of any one sensor by vehicles. Occupancy is defined as the number of consecutlve seconds that a `::
vehicle has been sensed as present by the sensor.
Density is defined as the percentage time in a given time interval that the loop has sensed the presence of a ,'-.: ':: .' --, ::' ~6~
vehicle or vehicles This information is then used to oalculate if a traffic incident has ocaurred in accordance with an algorithm Such algorithms are ~nown to those skilled in the art, as exemplified by ths high occupancy (HIOCC) algorithm developed by the Transport and Road Research Laboratory (T~RL) as disclosed in TRRL
supplementary reports Nos 775 (Automatic incident detection, experience with two TRRL algorithm HIOCC; J F
Collins 1983) and 526 (Automatic inoident deteotion -TRRL algorithms HIOCC and PATREG; J F Collins, C M
Hopkins and J A Martin 1979) The HIOCC algorithm as disclosed in the above documents, the contents of which are incorporated herein by reference, operates by detecting stationary or slow moving vehicles to indicate a traffic queue caused by an incident or by congestion It looks for several ~ -oonsecutive seconds of high detector occupancy to detect queues and ino1dents in high traffio flows A programme ~
in acoordance with the flow diagram of Figure 3 of ~ ;
r-port 526 is stored in ROM in site oontroller 120 and -~ `
CPU 310 processes the oooupancy data from VDMs 120 - 124 in acoordance with the programmed algorithm The resultant occupancy, denslty and incident data is stored locally in data cartridge 320 and is also sent to the central oontroller 66 via data bus 90 When the algorlthm detects a trafflc lncident, an incident detection signal i8 sent both to the central controller and to the camera controller 60 associated with the site controller 100. The incident detection signal causes the oamera controller to freeze a predetermined number of image~ in the frame store 84 as previously descrlbed, thus provlding a stored record of the circumstances leading up to the incldent as detected by the incident detector.
In addition to the HIOCC algorithm, the site controller uses a speed (as opposed to occupancy) based algorithm using two ad~acent loop sensors eg 41, 43 in any one lane. Such an algorlthm provides additional information concerning slow moving vehicles - whi¢h are, in themselves, a traffic hazard. Furthermore, by basing analysi~ on speed, speeding violations may also be :: ~
detected.
An example of a suitable algorithm is as follows:
.:
Two measurement intervals Tl and T2 (between one minute i ' and twenty fqur hours depending on occupancy) are chosen, interval Tl representing a relatively longer perlod than T2. Uslng ~djacent loop detectors 41, 43 the average speed in each interval Tl, T2 is calculated and updated as each vehicle passes, givlng average speeds S1, S2. The difference between these speeds (Sl ., . . . . ~ . .
14 25~ G~
-S2) glves an indication of short term speed variation away from the long term average and if over a predetermined threshold SD gives an indication of an incident. Furthermore, if S1 or S2 or the instantaneous vehicle speed fall outside predetermined high or low speed thresholds THH, THL, this also gives an indication of a probable incident. Examples of suitable parameters are T1 = 1 hour, T2 = 6 minutes, SD = 5 kph, THH = 200 ~ kph, THL ~ 20 kph.
;~ - , The site controllers 100, 102, 104 form nodes of a local area network (LAN) having a standard format and operating protocols, each node passing messages along ~ -the data bus 90. Each controller has a unique network identifier, with identifiers being reserved for ~all stat~ons~ called and the central control 66.
h~- topology of the networX is a daisy chain with out go1ng~message~ being passed to the end of the line and naomlng~messages belng passed back to the central controller 66. Each site oontroller is responsible for passing messagès along the line when a character arrives i~ it is bufered until the whole message is complcte. It is then retransmitted.
~ ~ .
A1l s1t- controllers examine me6~ages, discard corrupt ~;
m-ssage~, accept tho~e w1th matching addresses and pass on others.
When a site controller has a message of its own for the central controller 66, it tests the status of the incoming line from the previous site controller. If the line is busy, the site controller will continue to re-tranmsit data from the previous site controller until the line is clean, at whlch point the site controller will aommence transmission of its own message. During thi~ tlme any incoming me~ages from the outlying site controllers will be buffered in the 6ite controller UART
for re-transmission at the earliest opportunity.
Site controllers are assigned unique addresses and all , messages from site controllers to the central controller 66 are tagged with this address. Messages from the central controller to slte controllers are either 'all ~"
-~ ~ stations' to all site controllers or 'addressed' to ~: .
individual site controller8.
Me-8ageo are transmitted along the LAN as the data field of a network packet, packets having the following format:
i~` ' 1. Packet header 2. Destination address 3. Source address 4. Control flag :`
A: Acknowledgement B: Text mes~age `:`l`' 16 2~ 6Q~3 C: Incident detection/alarm mes~age D: Status message 5. Field check sum 6. Data box size 7. Data block The packet receiving protocol for each site controller is as follows:
1. Each complete message is re-transmitted along the line.
2. Incoming characters are also placed into the incoming message buffer.
3. When a full packet is received the unit compares the destination address with its own node id. -~ -~
4. If the id and address do not match no further action is taken.
5.~ If the id and address match then the packet iB
interpreted, involving the following:
A. The oh-cks ar- miscalculated ~ -` B. If the cheok sum is incorrect a bad packet error is flagged C. Th- response to a bad packet error is to do nothing and allow the souroe to time out and resend D. If the checks are incorrect, the data block is passed to the CPU for action and an acknowledgement ~, ~ (ACR) packet is sent to the central controller.
: .
The packet sending protocol of the site controllers is as follows:
1. The messages are formatted by the site controller CPU into a p~cket having the form noted above.
2. The packet is placed in an outgoing packet queue and the count of re-tries set to zero.
3. The packet is transmitted.
4. If an ACX packet i8 received from the target node/central controller with the correct packet ID then the packet has been successfully transmitted and is removed from the queue.
If no reply is received before a predetermined time out then the packet is re-sent and the count of retries for this packet is incremented.
If the count of time out re-tries reaches the user opecified maximum then a message time out error is flagged.
During normal operation when no incident detections are present the central controller 66 will poll the status of each site controller by sending a request for a status packet. In reply to the status request the units will respond with a data packet giving the following parameters:
1. Occupancy (the number of consecutive seconds for which a sensor has been found to be occupied).
2. Density: the percentage of tlme at a given lnterval for which the loop has been occupied.
3. Incident detection status.
4. Loop status.
S. Mislcellaneous.
When an inaident detection signal is generated, the sensing unit sends an incident detection packet to the central controller 66. The central controller 66 ~: ;
acknow~edges receipt of the pa¢ket (otherwise the packet is re-sent). The central controller then acts to freeze the memory store for the relevant camera/camera controller. In parallel, an incident detection signal i8 sent direct from the site controller to its associated ¢amera controller.
While the embodiment of the invention as described above ha~be-n appli-d to a road traffic sensing sy8tem, this not~to be~construed as limltative. For example, the ~ ~:
invention may be used in a driver's cab of a train, the incident detector being respon8ive to an automatic warnIng system (AW6) 'line ocoupied' signal showing, for xample, wh-n a train has gone through a danger signal.
Alternatively, the lnoident detector could be a sensor aonnected to the front buffers 0f the train 80 that data 18 stored on impact w1th another vehicle or ob~ect on 19 ~6C~
the track. In suah cir¢um~tances, the data cartrldge could be made to 'black box' ~tandards.
~: ~
;~
:: . - :
. -,.: :
;, "',; ~'.
Claims (25)
1. Monitoring apparatus comprising:
a camera, an image memory for storing images from the camera, an incident detector for generating an incident detection signal when an incident occurs, the image memory being responsive to the detection signal whereby a plurality of said images prior to the incident are identified; and means for reviewing said prior images.
a camera, an image memory for storing images from the camera, an incident detector for generating an incident detection signal when an incident occurs, the image memory being responsive to the detection signal whereby a plurality of said images prior to the incident are identified; and means for reviewing said prior images.
2. Apparatus as claimed in Claim 1 wherein the camera comprises a video camera.
3. Apparatus as claimed in Claim 1 wherein the image memory is divided into a plurality of fields each field storing an image frame.
4. Apparatus as claimed in Claim 3 wherein the stored frames are spaced by a time period greater than forty milliseconds.
5. Apparatus as claimed in Claim 3 wherein the time period between frames is variable.
6. Apparatus as claimed in Claim 3 wherein the number of frames stored is 2n, where n is greater than 1.
7. Apparatus as claimed in Claim 3 wherein the image memory comprises a first in first out stack.
8. Apparatus as claimed in Claim 3 wherein a part or all of the frames of the image memory are frozen in response to the detection signal.
9. Apparatus as claimed in Claim 1 wherein the image memory forms part of a camera controller connected to the camera and to the reviewing means.
10. Apparatus as claimed in Claim 9 wherein the camera controller is selectable to supply either said prior images or post incident images or real time images from the camera to the reviewing means.
11. Apparatus as claimed in Claim 1 wherein the reviewing means is remote from the camera.
12. Apparatus as claimed in Claim 1 wherein the reviewing means comprises a video monitor.
13. Apparatus as claimed in Claim 1 further comprising at least one further camera, each further camera having a respective image memory for storing images from the camera, a plurality of further incident detectors at least one incident detector being operably associated with each camera.
14. Apparatus as claimed in Claim 13 where further comprising a central control means for receiving incident detection signals from the detectors and prior images from the cameras.
15. Apparatus as claimed in Claim 14 wherein the central control means and reviewing means are disposed at the same location.
16. Apparatus as claimed in Claim 14 wherein the incident detectors are connected to the central control means via a common information transfer bus.
17 Apparatus as claimed in Claim 13 wherein the detector associated with each camera has a direst connection thereto for sending the detection signal to the camera.
18. Apparatus as claimed in Claim 1 wherein the incident comprises a traffic hazard.
19. Apparatus as claimed in Claim 18 wherein the incident detector comprises at least one vehicle sensor for generating a vehicle sensing signal and processing means for receiving said sensing signal and for determining from the signal if an incident has occured.
20. Apparatus as claimed in Claim 19 wherein more than one vehicle sensor is connected to the processing means.
21. Monitoring apparatus comprising a plurality of monitoring stations each having a camera and a localised camera controller, the camera controllers each having an image memory for storing images from the camera; and a remote central controller connected to the camera controllers for selectively receiving said stored images.
22. A method of determining the existence of a traffic incident comprising the steps of measuring the average speed of vehicles passing a sensor in a first time period, measuring the average speed of vehicles passing the sensor in a second time period shorter than the first time period, calculating the difference between the average speeds for the two time periods and of generating an incident detection signal when the difference is above a predetermined threshold.
23. A method as claimed in Claim 22 wherein the first time period is an order of magnitude larger than the second time period.
24 24. A method as claimed in Claim 22 wherein said average speeds are continuously updated.
25. A method as claimed in Claim 22 further comprising the step of comparing the average speeds to first and second thresholds and generating an incident detection signal when the average speeds fall above the first threshold or below the second threshold.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8910419.4 | 1989-05-05 | ||
| GB8910419A GB2231753A (en) | 1989-05-05 | 1989-05-05 | Traffic incident monitoring with vido cameras |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2016088A1 true CA2016088A1 (en) | 1990-11-05 |
Family
ID=10656310
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2016088 Abandoned CA2016088A1 (en) | 1989-05-05 | 1990-05-04 | Monitoring apparatus |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0396432A3 (en) |
| CA (1) | CA2016088A1 (en) |
| GB (1) | GB2231753A (en) |
Families Citing this family (25)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT398011B (en) * | 1989-06-08 | 1994-08-25 | Alcatel Austria Ag | DEVICE FOR MONITORING SPEED LIMITS OF TRAFFIC PARTICIPANTS |
| FR2667710B1 (en) * | 1990-10-05 | 1994-09-02 | Francis Guillot | DEVICE FOR DETECTING ANOMALIES OF INTEGRATED TRAFFIC ON SITE IN A CABINET. |
| ATE203844T1 (en) * | 1992-03-20 | 2001-08-15 | Commw Scient Ind Res Org | OBJECT MONITORING SYSTEM |
| NL9300671A (en) * | 1993-04-20 | 1994-11-16 | Gatsometer Bv | Method and device for electronically recording an event, for example a traffic violation. |
| KR100234851B1 (en) * | 1994-03-24 | 1999-12-15 | 타테이시 요시오 | Vehicle image pick-up system and vehicle image pick-up method |
| US5982418A (en) * | 1996-04-22 | 1999-11-09 | Sensormatic Electronics Corporation | Distributed video data storage in video surveillance system |
| GB2320389B (en) * | 1996-12-12 | 2000-08-09 | Leo Dickinson | Video recording device |
| FR2763726B1 (en) * | 1997-05-20 | 2003-01-17 | Bouchaib Hoummadi | METHOD FOR MANAGING ROAD TRAFFIC BY VIDEO CAMERA |
| FR2785432B1 (en) * | 1998-10-30 | 2001-01-19 | Citilog | METHOD FOR ANALYZING THE CONDITION OF A TRACK PORTION AND ITS ENVIRONMENT |
| GB2352072A (en) * | 1999-06-23 | 2001-01-17 | Abbas Haydari | Recording and playback system |
| CN100533482C (en) | 1999-11-03 | 2009-08-26 | 特许科技有限公司 | Image processing techniques for a video based traffic monitoring system and methods therefor |
| EP1189442A3 (en) * | 2000-09-13 | 2003-04-09 | Dynamit Nobel GmbH Explosivstoff- und Systemtechnik | Surveillance of an area by still image collating |
| DE50010935D1 (en) * | 2000-12-30 | 2005-09-15 | Goddert Peters | Tunnel monitoring system in a tunnel |
| JP3788400B2 (en) * | 2002-07-19 | 2006-06-21 | 住友電気工業株式会社 | Image processing apparatus, image processing method, and vehicle monitoring system |
| US7986339B2 (en) * | 2003-06-12 | 2011-07-26 | Redflex Traffic Systems Pty Ltd | Automated traffic violation monitoring and reporting system with combined video and still-image data |
| WO2005034060A1 (en) * | 2003-10-09 | 2005-04-14 | Moreton Bay Corporation Pty Ltd | System and method for image monitoring |
| FR2884018A1 (en) * | 2005-03-31 | 2006-10-06 | Neavia Technologies Soc Par Ac | Impeding object e.g. damaged vehicle, presence detecting method for use on road segment, involves counting vehicles present on segment and controlling automatic activation of image processing based on counting |
| ATE483220T1 (en) * | 2006-11-15 | 2010-10-15 | Aitek S P A | METHOD AND DEVICE FOR DETERMINING THE DISTANCE BETWEEN TWO VEHICLES DRIVING ON A ROAD OR A SECTION OF MOTORWAY, PARTICULARLY IN A TUNNEL |
| DE102007044820B4 (en) * | 2007-09-20 | 2009-06-18 | Insta Elektro Gmbh | Bus system and method for its operation |
| FR2928221B1 (en) | 2008-02-28 | 2013-10-18 | Neavia Technologies | METHOD AND DEVICE FOR MULTI-TECHNOLOGY DETECTION OF A VEHICLE |
| CN102682601B (en) * | 2012-05-04 | 2014-02-26 | 南京大学 | Expressway traffic incident detection method based on optimized support vector machine (SVM) |
| WO2017116325A1 (en) * | 2015-12-30 | 2017-07-06 | Hasan Kalyoncu Universitesi | Real time vehicle detection through highway tunnels |
| CN105788269A (en) * | 2016-05-12 | 2016-07-20 | 招商局重庆交通科研设计院有限公司 | Unmanned aerial vehicle-based abnormal traffic identification method |
| NO342011B1 (en) * | 2016-06-16 | 2018-03-12 | Roxel Aanestad As | Tunnel monitoring system and method of operation |
| CN107507414B (en) * | 2017-07-05 | 2020-12-11 | 湖北鑫美企业发展股份有限公司 | Cross road traffic flow monitoring device |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2082432A5 (en) * | 1970-03-16 | 1971-12-10 | Evr | |
| IT1095061B (en) * | 1978-05-19 | 1985-08-10 | Conte Raffaele | EQUIPMENT FOR MAGNETIC REGISTRATION OF CASUAL EVENTS RELATED TO MOBILE VEHICLES |
| DE3015737A1 (en) * | 1979-04-30 | 1980-11-13 | Eumig | Motor car monitor with TV camera - has floating head magnetic memory coupled to camera, with interference switch and storage selector |
| GB2064189A (en) * | 1979-11-09 | 1981-06-10 | Ascotts Ltd | Surveillance System |
| DE3333078A1 (en) * | 1983-09-14 | 1985-03-21 | Atis Assmann GmbH, 6380 Bad Homburg | VIDEO SURVEILLANCE |
| FR2593309B1 (en) * | 1986-01-23 | 1990-02-16 | Gestion Inf Nle Et | DEVICE AND METHOD FOR REMOTE MONITORING OF SITES INCLUDING MEANS FOR DETECTION OF ABNORMAL EVENTS, MEANS FOR LISTENING TO PHONES AND MEANS FOR VIDEO OBSERVATION |
| WO1988009023A1 (en) * | 1987-05-08 | 1988-11-17 | Viktor Szabo | Accident data recorder |
-
1989
- 1989-05-05 GB GB8910419A patent/GB2231753A/en not_active Withdrawn
-
1990
- 1990-05-04 CA CA 2016088 patent/CA2016088A1/en not_active Abandoned
- 1990-05-04 EP EP19900304912 patent/EP0396432A3/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB2231753A (en) | 1990-11-21 |
| EP0396432A3 (en) | 1991-04-10 |
| EP0396432A2 (en) | 1990-11-07 |
| GB8910419D0 (en) | 1989-06-21 |
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