CA2134659A1 - Device for testing the operability of speed-measurement devices used in traffic control - Google Patents
Device for testing the operability of speed-measurement devices used in traffic controlInfo
- Publication number
- CA2134659A1 CA2134659A1 CA 2134659 CA2134659A CA2134659A1 CA 2134659 A1 CA2134659 A1 CA 2134659A1 CA 2134659 CA2134659 CA 2134659 CA 2134659 A CA2134659 A CA 2134659A CA 2134659 A1 CA2134659 A1 CA 2134659A1
- Authority
- CA
- Canada
- Prior art keywords
- speed
- error
- sensors
- errors
- vehicles
- 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
- G08G1/01—Detecting movement of traffic to be counted or controlled
- G08G1/052—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed
- G08G1/054—Detecting movement of traffic to be counted or controlled with provision for determining speed or overspeed photographing overspeeding vehicles
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
- G01P21/00—Testing or calibrating of apparatus or devices covered by the preceding groups
- G01P21/02—Testing or calibrating of apparatus or devices covered by the preceding groups of speedometers
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Traffic Control Systems (AREA)
Abstract
Stationary speed-measurement devices used in traffic control have sensors laid in the road surface which react to vehicles that pass over them and which generate speed measurement values; when an admissible speed limit is exceeded by a vehicle driving over the sensors, a picture of the vehicle is taken by a camera. In order to test the operatability of such speed measurement devices, error recognition means prevent the speed measurement values from being taken into account when certain error criteria occur.
Counters are provided for counting the frequency of occurrence of error criteria. A determined statistical distribution of the occurrences of the various error criteria results for each installation.
When deviations from this distribution are detected, that means that the installation needs to be modified.
Counters are provided for counting the frequency of occurrence of error criteria. A determined statistical distribution of the occurrences of the various error criteria results for each installation.
When deviations from this distribution are detected, that means that the installation needs to be modified.
Description
.. `` ,~ l ? 1l~ fi '~ 9 AMENDED SHEETS
Method for testing the operability of speed measuring devices fGr traffic control Te hnical Field The in~ention relates to a method of testing the operability of stationarily installed speed measuring devices for traffic control, with which devices sensors are ~uried in the road surface. the sensors responding to vehicles passing thereover, signal processing means being provided, to which the sensor means can be connected and which provide speed measuring value~, taking ~ picture of a vehicle by the camera being triggered, if the~ passing vehicle exceeds a permissible ; maximum speed, the signal processing means containing error detection~ means which` prevent the taking into account of the 2~ speed m~asuring values, lf certain errors occur.
Bac~round Art S~:at~ionar~ speed measuring devices are known far detecting the ~Z5 ~exceeding of permissible maximum speeds by vehicles~ These spe~ measuring devices contain sensors, which are buried in the road surface~at predetermined distance and which respond to;~vehicles passing thereover. Such sensors may be piezoelectric cables ~r cables otherwise sensitive to pressure (FR-~-Z,471,066; GB-A-?,084,774; EP-A-0,267,032). The sensors provide electric sensor signals, when the wheels of a vehicle pas -t~ereover. The speed can be d~termined by means of the ; signal processing means from the time interval between the sensor signals. If the vehicle speed thus measured exceeds a ~35 predetermined threshold, ~hich is equal to a permissible maximum speed, then the signal processing means cause the releasing of a photographic camera. The camera takes a picture 213~9 of the speeding vehicle. With this picture, also the license number and, if appropriate, also the driver are photoyraphed.
The neasured speed and other data (location, date and local time) are reflected into the photographic exposure. It is also 5 known to represent tis information by matrices of LEDs and to reflect the data during film feeding character-by-character onto the edge of the film (DE-C-3,034,161). Furthermore, it is known to place three sensors one behind the other (EP-B-0,042,546; "Radio Mentor Electronic" 44 (1978), 10-20, EP-A-0,387~0g3)~ The three sensors determine a total of three measuring distances: A first measuring distance extends between the first and second sensors, as viewed in the direction of motion of the traffic. A second measuring distance extends between the second and third sensors.
Eventually, a third measuring distance is obtained betwqen thefir~t and second sensors. It is known to derive speed measuring values from the time intervals betwe~n the sensor signals for all three measuring distances.
The speed measuring values may ~orm the basis of a proceeding for violation of traffic regulations. Therefore the speed ; ~measuring values have to stand court verification. Therefore, all~peed measuring values are discarded which could give rise to any doubts. Therefore, the signal processing means contain 2~ error recognition means which rate speed measuring values as . ~ ~
aulty in accordance with certain criteria. Normally the releasing of the camera is prevented with such speed measuring values rated as faulty. Such faulty speed measuring values are in no way recorded.
~30 The criteria according to which speed measuring values can be rated as faulty can be the following: A pulse from a sensor is ~- missing. The deviations of the speed measuring values obtained with the three measuring distances are too large. The first measuring pulse is not provided by the first sensor. Two sensors are triggered at approximately the sam~ time~
` 213~9 Furthermore, it is necessary to calibrate the installation accurately. This is a rather expensive procedure, which is carried ou~ by a calibration authority. The conditions at the installation site may, however, change in the course of time, for example due to dislocation of the road surface, changes of the subsoil etc. For this reason, it is necessary to check the operability of the device at comparatively large intervals.
Conventionally this is done by re-calibration. Such re-calibration~ again, is an expensive measure.
Disclosure of the Invention It is the object of the invention, with a device of the type defined in the beginning, to check the operability of the device in a simple way and to avoid expensive re-calibration at least in the majority of cases.
:~ :
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~ A~cording to the invention, this object is achieved in that :
~ (a) a number of different error criteria are observed, , (b) the frequency of the occurrence of these different error criteria prior or shortly after the deployment of the installation is recorded as an error distribution typical for the installation site on the :
basis of ~ number of measurements sufficiently large or statistical purposes, (c) the instantaneous error distribution during operation is determined at predetermined intervals and is compared with the recorded, initial error distribution, significant differences of this error distributions pointing at changes at the speed measuring device or its environment.
The invention is based on the realisation that the various error criteria, in the statistical mean of a rather large ~ ` 213~6~9 number of measurements, provides a typical frequency distribution of the errors for each particular installation.
This fre~uency distribution represents a kind of "fingQrprint"
of the installation. Such a frequency distribution is determined immediately following the first calibration or prior to this first calibration. As long as this frequency distribution remains substantially unchanged in the course of time, i.e. for months, it can be assumed that also the installation itself has remained substantially u~changed. If, however, the frequency distribution of the errors changes significantly, this will point to variations in the function or structure of the installation. Then a check or, if necessary, re-calibration of the installation has to take place.
While, with the prior art installations, the errors recognized ;in ~accordance with various criteria merely cause the assoc~iated speed measuring value to be discarded, according to the invention the operation of the installation is monitored on a~ long time basi~s by~means of error statistics. The errors ccùr ~also with perfectly operating and freshly calibrated inst~llations. But de~iations from a frequency distribution of hese~errors typical o~ the particular installation are used as~a criterion of changes in the installation.
25~
Modifications of the ~invention are subject matter of the depen~ent claims.
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An~embodiment of the invention is described in greater detail hereinbelow with reference to the accompanying drawings.
Brlef;Description of the Drawinqs ; Fig.1 ~shows a block diagram of a speed measuring device with a device for statistically testing its operability.
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Fig.2 shows typical signal waveforms as obtained with sensors of ~he speed measuring devi~e sf Fig.1.
Fig.3 shows a diagram of the error distribution, which diagram is characteristic of a particular speed measuring device at a particular measuring site.
Pre~erred Embodiments of the Invention The Speed measuring device contains three sensor~ 10, 12 and 14 buried in the road surface with fixed spacings one behind the other. The sensors 10, 12 and 14 are piezoelectric cables, which extend transversely across the road or one half of the road. The sensors lo, 12 and 14 generate signals, when a vehicle passes thereover. Fig.2 shows typical siynals as *hey~are obtained in normal operat;ion in two: neighboring ~ensors, for example the sensors 10 and 12. ~ Each signal exhibits a first peak 16 or 18, respectively, and a~ second peak 20 or 22, respectively. The first~peaks are caused ~by the front wheels of the vehicle.
The~ second: peaks~ are caused by the rear wheel~ of the vehicle. The signals represent dying-out os~illations. The :respeotive front:edges~ of the signa~s serve as ~easuring points. For ~the speed measurement, the~ time intervals between~signals provided by the various sensors lO, 12 and 14, ~or example 16 and 18, are measuredO This is achieved : ~ , by~means of three ~ounters 24, 26 and 28. The coun~er 24 is started by the signal 16 of sensor 10 and counts counting : pul~es, which are provide a~ high frequency, by a quartz-controlled oscillator. The counting is stopped ~y the signal 18 from the neighboring counter. The ```~ 21346!~9 counter 26 is started by the signal 18 of the second sensor 12O Then the counter 26 also counts counting pulses, which are provided at a high frequency by a quartz-controlled oscillator. The counter 26 is stopped by the first signal of the third sensor 14. Eventually, the counter 28 is started by the signal of the first sensor 10 and also counts counting pulse~ at a high frequency from a quartz controlled oscillator. The counter 28 is stopped by the first signal of the third sensor. Thereby, the counts provide measures of the time which the vehicle required to cover the measuring distan~es between the first and second sensors 10 and 12, respectively, between the second and the third sensors 12 and 14, respectively, and between the first and the second sensors 10 and 14, respectively. A computer determines the speed from these times and the known lengths of the measuring distances in accordance with the relation speed equals distance divided by time. This value is displayed by means of a display device 32~ If the o~tained speed measuring value wxceeds a predetermined threshold corresponding to the permissible ~maximum speed, a camera 36 is released through an output 34.
The~threshold, at which, if exceeded, a photographic exposure is~tri~geredr is set by an input device 3~.
Th~speed measuring device includes error recognition means ~25 ~ 40.~ The error recogni~tion means 42 include error analysing means,~ which are~ illustrated by a correspondingly marked blo~k. The signals of the three sensors 10, 12 and 14 are applied~ to the error analysing means 42. The error analysing means~ recognize errors of an error type "1" and error os an 3~ error type "2". An error of error type "1" is present, !if two ; or all sensors provide a signal simultaneously. Then a count ; of one of the counters 24, ?6 or 28 becomes zero.Such signals An then be caused by cross-talk between the sensors. An error of the error type "2" is present, if the siynals appear in the wrong sequence. Also in this case, the counters do not count any counting pulses. Then the signals may be caused by a vehicle driving in the opposite direction. In both cases, the ' 213~659 measuring value is suppressed by the error analysing means 42.
The camera is not released.
The errors of type "l" detected by the error analysing means 42 are counted in a counter 44. The errors of type "2"
detected by the error analysing means 42 are counted in a counter 48.
The counts which have not been discarded as faulty by the error analysing means 42 are supplied, as shown by arrows 50, to comparison means 52~ which are represented by a correspondingly marked block. The ~omparison means 52 compare the times determined by means of the counters 24, 26 and 28 ~or the speeds resulting therefrom). An error of type "3".
Such an error is present if the obtained speed measuring values deviate from each other by more than a certain amount, for example 3 km/h or 3 percent with speeds above lO0 km~h.Al~o in such a case, the speed measuring value is rated uncertain and is not taken into account. The camera is not triggered. Such deviations can, in particular, occur, if the vehi¢le decelerates while passing the measuring distances.
Also the number of detected errors of type "3" is counted by a counter 54. If none of the errors of types "l", 1'2" or 11311 has occurred, the time or speed measuring value is appli~d to the comput~:r 30.
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The~computer, eventually, detects errors of a type "4". These rrors consist in that npt all sensors lO, 12 and 14 have provided a signal. Also these errors are counted in a counter 56.
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also no error of type "4" is prèsent, the speed measuring value from the computer 30 is applied to an output register 58. If the speed measuring value exceeds the permissible maximum speed, the the computer 30 triggers the camera 36 through an output 60. The camera is a motor-driven recording camera.
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Furthermore, the computer controls a frame counter 62 which counts the number of exposures made. Furthermore, a local time and date display 64 is controlled by the computer.
Furthermore, the total number of the measured vehicles (whether exceeding the permissible maximum speed or not~ is counted by a counter 66. An ouput register 68 contains a code which identifies the respective installation. Eventually, the permissible maximum speed valid at the site of the installation is stored in an output register 70. Such data can be inputted into the computer through a keyhoard.
During normal operationj the camera 36 is released, when an excessive speed is detected. During the subsequent film feeding, information is transferred to the edge of the film through a LED-matrix controlled by the output registers. This :
is dvne in the way described in DE-A-3,034,161. When an excessive speed is detected in the normal way, the pattern shown in the right strip in Fig.1 is obtained. The displayed data are: the speed measuring value at the location 72, the current number of the frame from frame counter 62 at the location 74, local time and date from output register 64 at locatlon~76, the code from output register 68 at location 78, and~the maxomum speed from output register 70 at location 80.
~
A similar picture (calibration photograph) i5 taken, when the installation is calibrated for the first time.
Coun~ers 44, 48, 54 and 56 are provided for monitoring the operability of the installation. In addition, the counters 62 and 66 are used for this purpose. If, after a sufficiently large~number of observed vehicles, which permits statisticai evaluation, the total num~er of the observed vehicles, the ` number of the detected violations and the frequencies of the 35 various types of errors are plotted in a diagram of the kind o~ Fig.3, this will result in a partic~lar "waveform" 82. It has been found, that this waveform 82 is characteristic of a ` 2~34~59 particular installation and a particular installation site. At one location, the probability that the permissible maximum speed is exceeded is higher, for example due to the road situation, at some other location the probability is lower.
Accordingly, a certain ratio of the total number of vehicles and of the number of detected violations will ensue.
Similarly, there will be a certain probability for the occurrence of the various types of errors for each installation site and each installation. At one location, it is more likely that a driver decelerates or accelerates than at some other location. Correspondingly the fre~uency of an error of the type 113-- will vary. A similar situation exists with location-dependent probabilities that the sensors are actuated by passing vehicles driving in the opposite direction or that vehicles leaving or entering the lane actuate only one or two sensors. The ~requency of the occurrence of errors can also be due to the characteristics of the speed measuring device or, for example, to the road, in the road surface of which the sensors a~re buried. For example, ~ibrations can 2û ~ o~:cur in the road which falsify individual measured values. As long as this s$atistically detected "error profile" remains substantially unchanged, it can be assumed that there are no substantial changes~ of the installation. If~ however, deviations ~f this error profile occur, this will point to ;25 ~changes o~ the ins~allation or of its environment, which may necessitate checking or re-calibration.
:
; In ~order to obtain the "error profiles", the counts of the counters 44, 48, 54~and 56 and of the counters 62 and 66 are photographed in certain time intervals together with date and local time and the code by "statistical photographs". These statistical photographs are triggered either by the counter 200 after each 200 exposures, or by the clock after each 4 hoursO This is illustrated in Fig.l by the connections 84 and 86.
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`~` 2134!~59 The statistical photographs have a pattern as shown in Fig.1 by the left strip on the right side. The information is also transferred to the edge of the film by a LED-matrix during the fi~m feeding. The count of the counter 44 appears at location 8~. The count of the counter 48 appears at the location 90.
The count of the counter 54 appears at the location 92. The count of the counter 56 appears at the location 94. There is no recording of a speed measuring value or of a permissible maximum speed. However the number of the pictures taken from counter 62, date and lncal time from output register 64, the total number of the observed vehicles from counter 66 and the code from output register are recorded at the locations 74, 76, 96 and 78, respectively.
By means of a manually operated switch 98, a calibration photograph can be triggered manually. ~n the same way, a statistical photograph can be triggered by a manually operated switch 100.
The procedure of monitoriny the operability with the device described is as follows:
At ~irst, a first caIi~ration of the installed installation is made by~the competent calibration authority, for example the 25;~ Physi~alisch-Technische Bundesanstalt. The calibration is d~Gumented, amon~ other ways, by calibration photographs.
Thereafter, the ~requencies of the errors of the various types and~ the total number of observed vehicles and the number of detected violations are determined~ during a statistical period of 200 e~posures or 4 hours, and are documPnted by a statistical photograph of the type illustrated in Fig.1~ Such ; a statistical photograph can also be triggered manually.
~ Therefrom, an error profile of the kind shown in Fig.3 can be ; obtained. The data thus obtained are placed in the records. At certain intervals, the newly obtained statistical photographs and error profiles are compared with the data in the records.
In case that this reveals significant deviations, re-:' `"' 21346!~9 calibration can be effected. Such re-calibration may, however, be unnecessary. as long as the statistical photographs provide substantially the same error profiles as those obtained immediately after the first calibration. The statistical photographs are triggered automatically.
;~ :
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Method for testing the operability of speed measuring devices fGr traffic control Te hnical Field The in~ention relates to a method of testing the operability of stationarily installed speed measuring devices for traffic control, with which devices sensors are ~uried in the road surface. the sensors responding to vehicles passing thereover, signal processing means being provided, to which the sensor means can be connected and which provide speed measuring value~, taking ~ picture of a vehicle by the camera being triggered, if the~ passing vehicle exceeds a permissible ; maximum speed, the signal processing means containing error detection~ means which` prevent the taking into account of the 2~ speed m~asuring values, lf certain errors occur.
Bac~round Art S~:at~ionar~ speed measuring devices are known far detecting the ~Z5 ~exceeding of permissible maximum speeds by vehicles~ These spe~ measuring devices contain sensors, which are buried in the road surface~at predetermined distance and which respond to;~vehicles passing thereover. Such sensors may be piezoelectric cables ~r cables otherwise sensitive to pressure (FR-~-Z,471,066; GB-A-?,084,774; EP-A-0,267,032). The sensors provide electric sensor signals, when the wheels of a vehicle pas -t~ereover. The speed can be d~termined by means of the ; signal processing means from the time interval between the sensor signals. If the vehicle speed thus measured exceeds a ~35 predetermined threshold, ~hich is equal to a permissible maximum speed, then the signal processing means cause the releasing of a photographic camera. The camera takes a picture 213~9 of the speeding vehicle. With this picture, also the license number and, if appropriate, also the driver are photoyraphed.
The neasured speed and other data (location, date and local time) are reflected into the photographic exposure. It is also 5 known to represent tis information by matrices of LEDs and to reflect the data during film feeding character-by-character onto the edge of the film (DE-C-3,034,161). Furthermore, it is known to place three sensors one behind the other (EP-B-0,042,546; "Radio Mentor Electronic" 44 (1978), 10-20, EP-A-0,387~0g3)~ The three sensors determine a total of three measuring distances: A first measuring distance extends between the first and second sensors, as viewed in the direction of motion of the traffic. A second measuring distance extends between the second and third sensors.
Eventually, a third measuring distance is obtained betwqen thefir~t and second sensors. It is known to derive speed measuring values from the time intervals betwe~n the sensor signals for all three measuring distances.
The speed measuring values may ~orm the basis of a proceeding for violation of traffic regulations. Therefore the speed ; ~measuring values have to stand court verification. Therefore, all~peed measuring values are discarded which could give rise to any doubts. Therefore, the signal processing means contain 2~ error recognition means which rate speed measuring values as . ~ ~
aulty in accordance with certain criteria. Normally the releasing of the camera is prevented with such speed measuring values rated as faulty. Such faulty speed measuring values are in no way recorded.
~30 The criteria according to which speed measuring values can be rated as faulty can be the following: A pulse from a sensor is ~- missing. The deviations of the speed measuring values obtained with the three measuring distances are too large. The first measuring pulse is not provided by the first sensor. Two sensors are triggered at approximately the sam~ time~
` 213~9 Furthermore, it is necessary to calibrate the installation accurately. This is a rather expensive procedure, which is carried ou~ by a calibration authority. The conditions at the installation site may, however, change in the course of time, for example due to dislocation of the road surface, changes of the subsoil etc. For this reason, it is necessary to check the operability of the device at comparatively large intervals.
Conventionally this is done by re-calibration. Such re-calibration~ again, is an expensive measure.
Disclosure of the Invention It is the object of the invention, with a device of the type defined in the beginning, to check the operability of the device in a simple way and to avoid expensive re-calibration at least in the majority of cases.
:~ :
~ ::
~ A~cording to the invention, this object is achieved in that :
~ (a) a number of different error criteria are observed, , (b) the frequency of the occurrence of these different error criteria prior or shortly after the deployment of the installation is recorded as an error distribution typical for the installation site on the :
basis of ~ number of measurements sufficiently large or statistical purposes, (c) the instantaneous error distribution during operation is determined at predetermined intervals and is compared with the recorded, initial error distribution, significant differences of this error distributions pointing at changes at the speed measuring device or its environment.
The invention is based on the realisation that the various error criteria, in the statistical mean of a rather large ~ ` 213~6~9 number of measurements, provides a typical frequency distribution of the errors for each particular installation.
This fre~uency distribution represents a kind of "fingQrprint"
of the installation. Such a frequency distribution is determined immediately following the first calibration or prior to this first calibration. As long as this frequency distribution remains substantially unchanged in the course of time, i.e. for months, it can be assumed that also the installation itself has remained substantially u~changed. If, however, the frequency distribution of the errors changes significantly, this will point to variations in the function or structure of the installation. Then a check or, if necessary, re-calibration of the installation has to take place.
While, with the prior art installations, the errors recognized ;in ~accordance with various criteria merely cause the assoc~iated speed measuring value to be discarded, according to the invention the operation of the installation is monitored on a~ long time basi~s by~means of error statistics. The errors ccùr ~also with perfectly operating and freshly calibrated inst~llations. But de~iations from a frequency distribution of hese~errors typical o~ the particular installation are used as~a criterion of changes in the installation.
25~
Modifications of the ~invention are subject matter of the depen~ent claims.
- ~
An~embodiment of the invention is described in greater detail hereinbelow with reference to the accompanying drawings.
Brlef;Description of the Drawinqs ; Fig.1 ~shows a block diagram of a speed measuring device with a device for statistically testing its operability.
:
::
~ `, 21~465!~
Fig.2 shows typical signal waveforms as obtained with sensors of ~he speed measuring devi~e sf Fig.1.
Fig.3 shows a diagram of the error distribution, which diagram is characteristic of a particular speed measuring device at a particular measuring site.
Pre~erred Embodiments of the Invention The Speed measuring device contains three sensor~ 10, 12 and 14 buried in the road surface with fixed spacings one behind the other. The sensors 10, 12 and 14 are piezoelectric cables, which extend transversely across the road or one half of the road. The sensors lo, 12 and 14 generate signals, when a vehicle passes thereover. Fig.2 shows typical siynals as *hey~are obtained in normal operat;ion in two: neighboring ~ensors, for example the sensors 10 and 12. ~ Each signal exhibits a first peak 16 or 18, respectively, and a~ second peak 20 or 22, respectively. The first~peaks are caused ~by the front wheels of the vehicle.
The~ second: peaks~ are caused by the rear wheel~ of the vehicle. The signals represent dying-out os~illations. The :respeotive front:edges~ of the signa~s serve as ~easuring points. For ~the speed measurement, the~ time intervals between~signals provided by the various sensors lO, 12 and 14, ~or example 16 and 18, are measuredO This is achieved : ~ , by~means of three ~ounters 24, 26 and 28. The coun~er 24 is started by the signal 16 of sensor 10 and counts counting : pul~es, which are provide a~ high frequency, by a quartz-controlled oscillator. The counting is stopped ~y the signal 18 from the neighboring counter. The ```~ 21346!~9 counter 26 is started by the signal 18 of the second sensor 12O Then the counter 26 also counts counting pulses, which are provided at a high frequency by a quartz-controlled oscillator. The counter 26 is stopped by the first signal of the third sensor 14. Eventually, the counter 28 is started by the signal of the first sensor 10 and also counts counting pulse~ at a high frequency from a quartz controlled oscillator. The counter 28 is stopped by the first signal of the third sensor. Thereby, the counts provide measures of the time which the vehicle required to cover the measuring distan~es between the first and second sensors 10 and 12, respectively, between the second and the third sensors 12 and 14, respectively, and between the first and the second sensors 10 and 14, respectively. A computer determines the speed from these times and the known lengths of the measuring distances in accordance with the relation speed equals distance divided by time. This value is displayed by means of a display device 32~ If the o~tained speed measuring value wxceeds a predetermined threshold corresponding to the permissible ~maximum speed, a camera 36 is released through an output 34.
The~threshold, at which, if exceeded, a photographic exposure is~tri~geredr is set by an input device 3~.
Th~speed measuring device includes error recognition means ~25 ~ 40.~ The error recogni~tion means 42 include error analysing means,~ which are~ illustrated by a correspondingly marked blo~k. The signals of the three sensors 10, 12 and 14 are applied~ to the error analysing means 42. The error analysing means~ recognize errors of an error type "1" and error os an 3~ error type "2". An error of error type "1" is present, !if two ; or all sensors provide a signal simultaneously. Then a count ; of one of the counters 24, ?6 or 28 becomes zero.Such signals An then be caused by cross-talk between the sensors. An error of the error type "2" is present, if the siynals appear in the wrong sequence. Also in this case, the counters do not count any counting pulses. Then the signals may be caused by a vehicle driving in the opposite direction. In both cases, the ' 213~659 measuring value is suppressed by the error analysing means 42.
The camera is not released.
The errors of type "l" detected by the error analysing means 42 are counted in a counter 44. The errors of type "2"
detected by the error analysing means 42 are counted in a counter 48.
The counts which have not been discarded as faulty by the error analysing means 42 are supplied, as shown by arrows 50, to comparison means 52~ which are represented by a correspondingly marked block. The ~omparison means 52 compare the times determined by means of the counters 24, 26 and 28 ~or the speeds resulting therefrom). An error of type "3".
Such an error is present if the obtained speed measuring values deviate from each other by more than a certain amount, for example 3 km/h or 3 percent with speeds above lO0 km~h.Al~o in such a case, the speed measuring value is rated uncertain and is not taken into account. The camera is not triggered. Such deviations can, in particular, occur, if the vehi¢le decelerates while passing the measuring distances.
Also the number of detected errors of type "3" is counted by a counter 54. If none of the errors of types "l", 1'2" or 11311 has occurred, the time or speed measuring value is appli~d to the comput~:r 30.
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~:
The~computer, eventually, detects errors of a type "4". These rrors consist in that npt all sensors lO, 12 and 14 have provided a signal. Also these errors are counted in a counter 56.
::
also no error of type "4" is prèsent, the speed measuring value from the computer 30 is applied to an output register 58. If the speed measuring value exceeds the permissible maximum speed, the the computer 30 triggers the camera 36 through an output 60. The camera is a motor-driven recording camera.
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~ 213~6~
Furthermore, the computer controls a frame counter 62 which counts the number of exposures made. Furthermore, a local time and date display 64 is controlled by the computer.
Furthermore, the total number of the measured vehicles (whether exceeding the permissible maximum speed or not~ is counted by a counter 66. An ouput register 68 contains a code which identifies the respective installation. Eventually, the permissible maximum speed valid at the site of the installation is stored in an output register 70. Such data can be inputted into the computer through a keyhoard.
During normal operationj the camera 36 is released, when an excessive speed is detected. During the subsequent film feeding, information is transferred to the edge of the film through a LED-matrix controlled by the output registers. This :
is dvne in the way described in DE-A-3,034,161. When an excessive speed is detected in the normal way, the pattern shown in the right strip in Fig.1 is obtained. The displayed data are: the speed measuring value at the location 72, the current number of the frame from frame counter 62 at the location 74, local time and date from output register 64 at locatlon~76, the code from output register 68 at location 78, and~the maxomum speed from output register 70 at location 80.
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A similar picture (calibration photograph) i5 taken, when the installation is calibrated for the first time.
Coun~ers 44, 48, 54 and 56 are provided for monitoring the operability of the installation. In addition, the counters 62 and 66 are used for this purpose. If, after a sufficiently large~number of observed vehicles, which permits statisticai evaluation, the total num~er of the observed vehicles, the ` number of the detected violations and the frequencies of the 35 various types of errors are plotted in a diagram of the kind o~ Fig.3, this will result in a partic~lar "waveform" 82. It has been found, that this waveform 82 is characteristic of a ` 2~34~59 particular installation and a particular installation site. At one location, the probability that the permissible maximum speed is exceeded is higher, for example due to the road situation, at some other location the probability is lower.
Accordingly, a certain ratio of the total number of vehicles and of the number of detected violations will ensue.
Similarly, there will be a certain probability for the occurrence of the various types of errors for each installation site and each installation. At one location, it is more likely that a driver decelerates or accelerates than at some other location. Correspondingly the fre~uency of an error of the type 113-- will vary. A similar situation exists with location-dependent probabilities that the sensors are actuated by passing vehicles driving in the opposite direction or that vehicles leaving or entering the lane actuate only one or two sensors. The ~requency of the occurrence of errors can also be due to the characteristics of the speed measuring device or, for example, to the road, in the road surface of which the sensors a~re buried. For example, ~ibrations can 2û ~ o~:cur in the road which falsify individual measured values. As long as this s$atistically detected "error profile" remains substantially unchanged, it can be assumed that there are no substantial changes~ of the installation. If~ however, deviations ~f this error profile occur, this will point to ;25 ~changes o~ the ins~allation or of its environment, which may necessitate checking or re-calibration.
:
; In ~order to obtain the "error profiles", the counts of the counters 44, 48, 54~and 56 and of the counters 62 and 66 are photographed in certain time intervals together with date and local time and the code by "statistical photographs". These statistical photographs are triggered either by the counter 200 after each 200 exposures, or by the clock after each 4 hoursO This is illustrated in Fig.l by the connections 84 and 86.
.
:: :
: :
`~` 2134!~59 The statistical photographs have a pattern as shown in Fig.1 by the left strip on the right side. The information is also transferred to the edge of the film by a LED-matrix during the fi~m feeding. The count of the counter 44 appears at location 8~. The count of the counter 48 appears at the location 90.
The count of the counter 54 appears at the location 92. The count of the counter 56 appears at the location 94. There is no recording of a speed measuring value or of a permissible maximum speed. However the number of the pictures taken from counter 62, date and lncal time from output register 64, the total number of the observed vehicles from counter 66 and the code from output register are recorded at the locations 74, 76, 96 and 78, respectively.
By means of a manually operated switch 98, a calibration photograph can be triggered manually. ~n the same way, a statistical photograph can be triggered by a manually operated switch 100.
The procedure of monitoriny the operability with the device described is as follows:
At ~irst, a first caIi~ration of the installed installation is made by~the competent calibration authority, for example the 25;~ Physi~alisch-Technische Bundesanstalt. The calibration is d~Gumented, amon~ other ways, by calibration photographs.
Thereafter, the ~requencies of the errors of the various types and~ the total number of observed vehicles and the number of detected violations are determined~ during a statistical period of 200 e~posures or 4 hours, and are documPnted by a statistical photograph of the type illustrated in Fig.1~ Such ; a statistical photograph can also be triggered manually.
~ Therefrom, an error profile of the kind shown in Fig.3 can be ; obtained. The data thus obtained are placed in the records. At certain intervals, the newly obtained statistical photographs and error profiles are compared with the data in the records.
In case that this reveals significant deviations, re-:' `"' 21346!~9 calibration can be effected. Such re-calibration may, however, be unnecessary. as long as the statistical photographs provide substantially the same error profiles as those obtained immediately after the first calibration. The statistical photographs are triggered automatically.
;~ :
: ~ :: : : :
~: ; 30 ~ ~ f ~
' ~
:
Claims (7)
1. A method for testing the operability of stationarily installed speed measuring devices for traffic control, with which devices sensors are buried in the road surface, the sensors responding to vehicles passing thereover, signal processing means being provided, to which the sensor means are connected and which provide speed measuring values, taking a picture of a vehicle by the camera being triggered, if the passing vehicle exceeds a permissible maximum speed, the signal processing means containing error detection means which prevent the taking into account of the speed measuring values, if certain errors occur, characterized in that (a) a number of different error criteria are observed, (b) the frequency of the occurrence of these different error criteria prior or shortly after the deployment of the installation is recorded as an error distribution typical for the installation site on the basis of a number of measurements sufficiently large for statistical purposes, (c) the instantaneous error distribution during operation is determined at predetermined intervals and is compared with the recorded, initial error distribution, significant differences of this error distributions pointing at changes at the speed measuring device or its environment.
2. A method as claimed in claim 1, characterized in that the occurrence of all or a plurality of the following errors are detected and are individually counted for each type of error:
-Two or more sensors provide signal simultaneously.
-The signals from the sensors appear in the wrong sequence.
-The speed values derived from the signals of three sensors spaced one behind the other deviate from each other by more than a predetermined amount.
-Not all sensors provide a signal.
-Two or more sensors provide signal simultaneously.
-The signals from the sensors appear in the wrong sequence.
-The speed values derived from the signals of three sensors spaced one behind the other deviate from each other by more than a predetermined amount.
-Not all sensors provide a signal.
3. A method as claimed in claim 1 or 2, characterized in that in addition, the number of the detected violations of the permissible maximum speed are counted as a statistical quantity which is characteristic for the installation site.
4. A method as claimed in anyone of the claims 1 to 3, characterized in that, in addition, the total number of the vehicles passing the speed measuring device are counted and the numbers of errors or violations, respectively, are referenced to this total number.
5. A method as claimed in claim 4, characterized in that the numbers of the errors or violations, respectively, are permanently stored, when a predetermined number of passing vehicles has been reached.
6. A method as claimed in claim 6, characterized in that the storing is effected either after the predetermined number of passing vehicles or after a predetermined time, depending on which event occurs first.
7. A method as claimed in anyone of the claims 1 to 6, characterized in that - vehicles, the error-free measured speed exceeds the permissible maximum speed are recorded on a film by means of a camera together with the measured speed.
- the errors are counted by associated counters and - the counts are transferred to the film for permanent storing.
- the errors are counted by associated counters and - the counts are transferred to the film for permanent storing.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4214595.3 | 1992-04-30 | ||
| DE19924214595 DE4214595A1 (en) | 1992-04-30 | 1992-04-30 | DEVICE FOR CHECKING THE OPERATIONALITY OF SPEED MEASURING DEVICES FOR TRAFFIC MONITORING |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2134659A1 true CA2134659A1 (en) | 1993-11-11 |
Family
ID=6458050
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2134659 Abandoned CA2134659A1 (en) | 1992-04-30 | 1993-04-29 | Device for testing the operability of speed-measurement devices used in traffic control |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0638194A1 (en) |
| CA (1) | CA2134659A1 (en) |
| DE (1) | DE4214595A1 (en) |
| WO (1) | WO1993022756A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR960003444A (en) * | 1994-06-01 | 1996-01-26 | 제임스 디. 튜턴 | Vehicle surveillance system |
| US6111523A (en) | 1995-11-20 | 2000-08-29 | American Traffic Systems, Inc. | Method and apparatus for photographing traffic in an intersection |
| US5948038A (en) | 1996-07-31 | 1999-09-07 | American Traffic Systems, Inc. | Traffic violation processing system |
| US5929787A (en) * | 1996-11-27 | 1999-07-27 | Mee; Gary L. | Vibration actuated traffic light control system |
| DE10049852A1 (en) * | 2000-10-09 | 2002-04-25 | Dirk Wagner | Traffic monitoring method, especially red light monitoring involves detecting forbidden movement of vehicle, transmitting picture of offence to central office for evaluation and sending fine notification to determined vehicle owner |
| CN103106798A (en) * | 2012-12-20 | 2013-05-15 | 黑龙江省电力有限公司信息通信分公司 | Image recognition triggering traffic speed measuring photograph system |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3022356A1 (en) * | 1980-06-14 | 1982-01-14 | Reinhold 7996 Meckenbeuren Fischer | SPEED MEASURING SYSTEM, ESPECIALLY FOR ROAD VEHICLES |
| CH676512A5 (en) * | 1988-07-14 | 1991-01-31 | Zellweger Uster Ag | |
| DK0387092T3 (en) * | 1989-03-10 | 1996-07-01 | Franz Josef Gebert | Traffic monitoring equipment |
| GB9111931D0 (en) * | 1991-06-04 | 1991-07-24 | Lucas Ind Plc | Method of and apparatus for checking speed measurement |
-
1992
- 1992-04-30 DE DE19924214595 patent/DE4214595A1/en not_active Withdrawn
-
1993
- 1993-04-29 WO PCT/EP1993/001035 patent/WO1993022756A1/en not_active Application Discontinuation
- 1993-04-29 EP EP93909860A patent/EP0638194A1/en not_active Withdrawn
- 1993-04-29 CA CA 2134659 patent/CA2134659A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1993022756A1 (en) | 1993-11-11 |
| EP0638194A1 (en) | 1995-02-15 |
| DE4214595A1 (en) | 1993-11-04 |
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