EP0635813A1 - Akustisches Auswertungsverfahren des Strassenfahrzeugsverkehrsflusses - Google Patents

Akustisches Auswertungsverfahren des Strassenfahrzeugsverkehrsflusses Download PDF

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Publication number
EP0635813A1
EP0635813A1 EP94420208A EP94420208A EP0635813A1 EP 0635813 A1 EP0635813 A1 EP 0635813A1 EP 94420208 A EP94420208 A EP 94420208A EP 94420208 A EP94420208 A EP 94420208A EP 0635813 A1 EP0635813 A1 EP 0635813A1
Authority
EP
European Patent Office
Prior art keywords
traffic
indicator
acoustic
sound signal
analysis
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.)
Withdrawn
Application number
EP94420208A
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English (en)
French (fr)
Inventor
Pierre Jean-Paul Gaetan Charlet
Jean-Luc Gorand
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Laboratoire Central des Ponts et Chaussees
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Laboratoire Central des Ponts et Chaussees
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Filing date
Publication date
Application filed by Laboratoire Central des Ponts et Chaussees filed Critical Laboratoire Central des Ponts et Chaussees
Publication of EP0635813A1 publication Critical patent/EP0635813A1/de
Withdrawn legal-status Critical Current

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    • 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

Definitions

  • the present invention relates to the technical field of controlling or evaluating the flow of traffic from road vehicles establishing themselves on a traffic lane in the general sense.
  • a traffic lane of a road or motorway nature comprises a determined number of traffic queues, so that the saturation level is only reached in a very exceptional manner.
  • the speed of the flow of vehicles decreases, causing local saturation of the traffic lane, it not only results in an inconvenience for the movement of users, but also an attack on their safety.
  • Numerous systems are known in the state of the art suitable for collecting information along a road axis to be monitored and transmitting this information in real time to a central station, from which it can be taken. intervention and / or prevention measures.
  • patent application FR-2 675 610 has proposed an installation for evaluating a traffic flow of road vehicles providing for placing at regular intervals, in edge of the lane, microphones which transform the acoustic information emitted by road traffic into an electrical signal intended to be transmitted to a central station.
  • the installation makes it possible to determine the state of traffic. It must be considered that this frequency band corresponds to the emission of the pneumatic-road contact. This acoustic emission is a function among other things, of the speed of the vehicles, but also of the nature of the coating placed at the right of the receiving point.
  • Such a solution therefore has the drawback of requiring a calibration of the installation at each detection point.
  • the present invention therefore aims to remedy the drawbacks set out above by proposing a method designed to ensure almost uninterrupted, even permanent, monitoring of the flow of road traffic and making it possible to detect different traffic conditions, with a view to evaluating at best the intervention measures to be taken.
  • Another object of the invention is to propose a method for evaluating road traffic over a non-negligible length of the traffic lane, while offering the advantage of having a low cost of installation, operation and maintenance.
  • Fig. 1 is a schematic plan view of a section of taxiway equipped with an installation implementing the evaluation method according to the invention.
  • Fig. 2 illustrates the evolution curves of the sound signal in dB, as a function of time in seconds, making it possible to highlight a characteristic of the invention.
  • Figs. 3A to 3C are curves showing a characteristic of the process according to the invention.
  • Fig. 4 is a diagram showing the evolution between the two acoustic indicators determined by the method according to the invention.
  • the method according to the invention is designed to acoustically control or evaluate the flow of traffic from established road vehicles, as illustrated in FIG. 1 , on a traffic lane 1 comprising at least one, and in the example illustrated, three traffic lanes 11 to 13 .
  • queue 11 is said to be slow, while queue 13 is considered to be fast queue, insofar as the direction of traffic is established from left to right.
  • the method according to the invention could be applied to assess the traffic flow establishing on track 2 in the opposite direction.
  • the method according to the invention aims to have at the edge of the traffic queue, called the slowest 11 , one or more microphones 3 distributed along the section of the traffic lane 1 to be monitored.
  • the microphones 3 are placed inside the emergency stop terminals which are generally located at the edge of the traffic lanes.
  • Each microphone 3 for example of the electret type, is connected to a processing device 4 which is connected to a central control station 5 via a communication link 6 ensuring for example the power supply to the detectors 3 and the transmission of information from devices 4 .
  • each processing device 4 comprises a stage 7 for amplifying and filtering the signal delivered by the associated microphone 3 .
  • Stage 7 is followed by a circuit 8 for converting the amplified signal into a logarithmic value, in order to obtain a linear scale in decibels.
  • the conversion circuit 8 is connected to a management module 9 managed by a microprocessor which is responsible, in particular, for sampling the signal, for example at the rate of 32 samples per second, and for digitizing them.
  • This module 9 which performs other functions explained in the description of the process which follows, is connected to a communication module 10 capable of transmitting the information to the central station 5 .
  • the method according to the invention aims to determine the characteristics of road traffic from the sound waves collected by the microphones 3 .
  • These sound waves originate, in particular, from the powerplant of vehicles and from the acoustic emission due to the contact of tires on the road. It should be noted that due to the sharp decrease in the acoustic level received, as a function of the distance from the microphone to the traffic lanes, the traffic noise from the distant lanes, namely 12 , 13 in the example illustrated, are masked by those of the nearest queue 1 file.
  • the sound signal S collected is divided into analysis intervals each having a duration T1 , T2, ... T i , for example equal to 6 minutes.
  • the analysis intervals are chosen to be consecutive over time.
  • the method according to the invention aims to determine two acoustic indicators making it possible to assess the state traffic flow.
  • the method according to the invention aims to define, in each interval T i , the difference between the maximum level Lmax and the minimum level Lmin of the sound signal S appearing in the corresponding analysis interval T i .
  • the sound signal received by each microphone comprises a succession of maxima and minima corresponding to the successive passages of vehicles in front of the microphone, at the right of which the acoustic power is maximum.
  • the instantaneous sound power is a function of the distance between the vehicles, the position of the vehicle closest to the microphone and the distance between the traffic axis and the microphone.
  • the difference between the maximum Lmax and minimum Lmin levels makes it possible to determine a first acoustic indicator P1 corresponding to the dynamics of the acoustic signal.
  • the dynamic indicator P1 is equal to 3.7 dB in the interval T1 , to 8.6 dB in the interval T2 and to 14.2 dB in the interval T i .
  • the difference between the maximum and minimum values depends only on the distance between the vehicles, as long as the microphones are installed in a fixed manner. It should be considered that the distance between vehicles is an increasing function with the speed of traffic. Indeed, for safety reasons, the speed of traffic determines the distance between vehicles.
  • the dynamics P1 of the signal therefore constitutes an acoustic indicator making it possible to distinguish either a concentration of vehicles around the microphone, if the value of the dynamics is low, or a relatively fluid circulation, if its value is high.
  • the indicators P1 detected during the intervals T1, T2, T i make it possible to observe respectively a strong slowdown, dense traffic or fluid traffic.
  • the method according to the invention aims to determine a second acoustic indicator P2 which makes it possible to know whether there is absence or presence of traffic on the monitored lane. Indeed, knowledge of the indicator P1 alone does not make it possible to know whether there is traffic. An absence of traffic could lead to a low value of the dynamics, which would be interpreted as a strong slowdown, when there is no traffic.
  • the presence indicator P2 corresponds to at least one given level L P of the sound signal which is reached during a predetermined fraction of the duration of the interval considered T i .
  • This acoustic indicator also makes it possible to assess the state of traffic, insofar as the sound energy emitted increases as a function of speed.
  • the values of the indicator P2 increase with the speed of the flow of vehicles due to the noise of the engines and the noise of tire-road contact.
  • the P2 indicator offers the advantage of overcoming differences in noise levels emitted by vehicles depending on their nature (heavy goods vehicles or passenger cars), while making it possible to assess the presence of vehicles according to a level acoustics reached or exceeded during a given time compared to the analysis time. It should be understood that the indicator P2 is not expressed as a function of absolute values recorded in a given time space, but is based on the percentage of appearance of one or more noise levels in a time interval predetermined.
  • the acoustic indicators P1 and P2 previously defined are compared with setpoints making it possible to assess the state of traffic flow. Indeed, the comparison with a set level of the acoustic indicator P1 makes it possible to detect traffic disturbances, while that carried out with the indicator P2 makes it possible to confirm the presence of a traffic flow. Knowledge of the two acoustic indicators P1, P2 is necessary and sufficient to assess the state of saturation or fluidity of a stream of vehicles.
  • this figure is called a histogram of cumulative values, and includes a GAUSS scale along the ordinate axis graduated as a percentage of the duration T i of the analysis, while the levels in decibels of the acoustic signal appear on the axis. of abscissa.
  • Acoustic indices L1, L2 , ..., Li , ..., L99 are thus obtained whose noise level is reached or exceeded during a corresponding fraction of the duration of the analysis.
  • the index L1 has a noise level which is reached or exceeded during 1% of the duration of analysis
  • the index L99 has a noise level which is reached or exceeded during 99% of the duration d 'analysis.
  • the L1 index therefore corresponds to the index evaluating nuisance noise
  • the L99 index evaluates the level of ambient noise on the site.
  • Figs. 3A to 3C illustrate three families of curves recorded at different times of the day and making it possible to highlight different traffic conditions.
  • Each curve corresponds to an analysis time T i , for example equal to 6 minutes.
  • the slope of each curve corresponds to the dynamics of the acoustic signal.
  • the dynamic indicator P1 is determined by making the difference between two acoustic indices L i , namely L99 and L1 and, preferably, between the indices L84 and L16 . Indeed, it was found that there is a good correlation with the speed for the closest indices surrounding the index L50 .
  • the choice of space L84-L16 makes it possible to increase the precision of the measurements.
  • the average acoustic index P1 is equal to 16 dB, 4dB and 7 dB respectively for the families of curves illustrated in Figs. 3A to 3C .
  • This method of determining the acoustic indicator P1 constitutes an improvement of the method consisting in determining the dynamics of the signal by the difference between the values Lmax and Lmin , due to the very different acoustic powers. issued by the various categories of vehicles.
  • the presence indicator P2 is obtained by taking an acoustic index substantially close to the index L50 .
  • the average presence index P2 is equal to 73 dB, 86 dB and 85 dB respectively for the families of curves illustrated in FIGS. 3A to 3C .
  • curves illustrated in FIG. 3A correspond to traffic recorded between 2 and 3 am.
  • the statistical distributions are random and the dynamic P1 (16 dB) is high, which indicates low traffic.
  • the curves which are shown in Fig. 3B corresponds to a traffic flow recorded between 7 a.m. and 7:30 a.m.
  • the low value of the dynamic index P1 (4 dB) indicates a saturation of the taxiway.
  • Fig. 3C which shows curves corresponding to a traffic recorded between 10 and 11 am, shows that the acoustic indicator P1 has a value (7 dB) slightly higher than that of the index determined in FIG. 3B .
  • the corresponding circulation is considered dense but more fluid than in the example illustrated in FIG. 3B .
  • the saturation of the traffic lane is characterized by a decrease in the value of the dynamic index P1 and by a change to a minimum value for the presence index P2 .
  • Fig. 4 illustrates, by way of example, the evolution of the presence indicator L50 as a function of the dynamic indicator L16 - L84 .
  • the existing relationship between the presence indicator P2 and the dynamic P1 makes it possible to detect critical traffic periods from a single noise measurement.
  • the following description gives an example of a method for determining the set points corresponding to significant traffic conditions.
  • the analysis of critical traffic conditions consists in analyzing the data recorded during periods of heavy traffic corresponding to a low value of the dynamic indicator P1 . In the example illustrated, it is chosen to analyze only the data when the dynamic indicator P1 has a value less than 7 dB (point M1 ).
  • the noise samples recorded, during the time when the dynamic indicator P1 is less than 7 dB, are accumulated in order to determine their distribution.
  • An acoustic index is then chosen, the noise level of which is reached or exceeded during a corresponding fraction of the analysis time.
  • the noise level chosen for the determination of the set point corresponds to the noise level which is reached or exceeded during 50% of the duration of analysis.
  • the setpoint value, for such a noise level is equal to 82.5 dB (point M2 ).
  • the dynamic indicator P1 unambiguously allows the detection of a concentration of vehicles near the monitoring point.
  • strong traffic disruptions corresponding to a dynamic indicator P1 ⁇ 7 dB in the example illustrated, the possibility of detecting different states of the traffic speed is given by the presence indicator P2 .
  • a decrease in the values of the presence indicator P2 indicates the increase in traffic blocking, while an increase in the level of the indicator P2 means an increase in the traffic flow.
  • FIG. 4 Such a principle appears clearly in FIG. 4 on which are placed the set points M1, M2 of the indicators P1 and P2 , namely 7 and 82.5 dB.
  • the set points M1, M2 define the coordinates of a point of rotation of a circle C centered on this point and divided, for example, into sectors numbered from 1 to 8 making it possible to detect different states of saturation of the channel.
  • the statistical study of the noise samples thus allows an evaluation of the state of the traffic flow based solely on the acoustic signal emitted by the flow of vehicles.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Traffic Control Systems (AREA)
  • Measurement Of Mechanical Vibrations Or Ultrasonic Waves (AREA)
EP94420208A 1993-07-21 1994-07-18 Akustisches Auswertungsverfahren des Strassenfahrzeugsverkehrsflusses Withdrawn EP0635813A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR9309197 1993-07-21
FR9309197A FR2708123B1 (fr) 1993-07-21 1993-07-21 Procédé d'évaluation par voie acoustique de l'écoulement du trafic de véhicules routiers.

Publications (1)

Publication Number Publication Date
EP0635813A1 true EP0635813A1 (de) 1995-01-25

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EP94420208A Withdrawn EP0635813A1 (de) 1993-07-21 1994-07-18 Akustisches Auswertungsverfahren des Strassenfahrzeugsverkehrsflusses

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EP (1) EP0635813A1 (de)
FR (1) FR2708123B1 (de)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2864626A1 (fr) * 2003-12-30 2005-07-01 W2I Procede et systeme de mesure de la vitesse d'un vehicule, et support d'enregistrement pour leurs mises en oeuvre

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3573724A (en) * 1966-07-15 1971-04-06 Matsushita Electric Ind Co Ltd Traffic flow detecting apparatus
FR2675610A1 (fr) * 1991-04-18 1992-10-23 Alcuri Gustavo Procede et installation d'evaluation d'un flux de circulation de vehicules routiers.

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3573724A (en) * 1966-07-15 1971-04-06 Matsushita Electric Ind Co Ltd Traffic flow detecting apparatus
FR2675610A1 (fr) * 1991-04-18 1992-10-23 Alcuri Gustavo Procede et installation d'evaluation d'un flux de circulation de vehicules routiers.
WO1992018962A1 (fr) * 1991-04-18 1992-10-29 Gustavo Alcuri Procede et installation d'evaluation d'un flux de circulation de vehicules routiers

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2864626A1 (fr) * 2003-12-30 2005-07-01 W2I Procede et systeme de mesure de la vitesse d'un vehicule, et support d'enregistrement pour leurs mises en oeuvre
WO2005073736A2 (fr) * 2003-12-30 2005-08-11 Neavia Technologies Procede et systeme de mesure de la vitesse d'un vehicule
WO2005073736A3 (fr) * 2003-12-30 2006-03-30 Neavia Technologies Procede et systeme de mesure de la vitesse d'un vehicule

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Publication number Publication date
FR2708123B1 (fr) 1995-10-20
FR2708123A1 (fr) 1995-01-27

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