Communications: electrical – Traffic control indicator
Reexamination Certificate
1999-11-19
2002-04-02
Tweel, John (Department: 2632)
Communications: electrical
Traffic control indicator
C340S916000, C340S917000
Reexamination Certificate
active
06366219
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process and a device for the management of road traffic using the video camera as information source.
DESCRIPTION OF THE PRIOR ART
Measurement, regulation and monitoring are the principal tasks in traffic management.
Known as measurement devices are magnetic or inductive loops which are embedded in the roadway. These magnetic loops are formed of insulated copper wire coils of various sections creating a transducer that is sensitive to the presence of the metallic mass of a vehicle in its magnetic field. The sensitivity of the device is defined by the relative variation of the inductance upon passage of the vehicle over the loop and allows its detection. Said magnetic loops require grooving of the pavement for their definitive installation and maintenance. This type of operation is tedious and costly; it does not allow for upgrading nor leave room for any error. The surface tracking zone is relatively small. Installation requires interrupting traffic. All of the measurements derived from the identification of vehicular passage are punctual. The coverage of the surface by the vehicles cannot be evaluated. In the case of a waiting line of vehicles, the lack of vehicular presence over a magnetic loop does not enable identification of said waiting line. Neither pedestrians nor two-wheel vehicles are identified. The measurement is blind. The life expectancy of the magnetic loops is directly dependent on the state of the traffic and the roadway. Magnetic loops do not allow for self-diagnostics.
Known as measurement devices are pneumatic tubes which are in the form of rubber tubes. They are attached to the roadway perpendicular to the flow of traffic. Passage of the wheels of a vehicle causes a punctual compression which creates a pressure change inside the tube which is propagated to the ends so as to actuate an electric information identification contact. The vehicles are counted based on the number of pairs of wheels. These pneumatic tubes do not allow identification of multiple lanes of traffic nor can they distinguish trucks, two-wheel vehicles or pedestrians. The surface tracking zone is relatively small. All of the measurements derived from the identification of vehicular passage are punctual. The coverage of the surface by the vehicles cannot be evaluated. In the case of a waiting line of vehicles, the lack of vehicular presence over the pneumatic tube sensor does not enable identification of said waiting line. The measurement is blind. These pneumatic tubes are fragile and their life expectancy is very directly linked to the quality of the rubber, to the traffic and vandalism; it can range from several days to several months.
Known as measurement devices are piezoelectric sensors which are coaxial shielded cables constituted by a core and a copper sheath which are insulated from each other by a piezoelectric ceramic. Prior to their insertion in the roadway, these sensors must be packaged in a resin bar, the length of which corresponds to the width of the roadway. The weight of a vehicle creates a pressure variation which allows identification. Installation requires a specialized staff and traffic must be stopped for several hours. These piezoelectric sensors are sensitive to the mechanical stresses created by the pressure of the vehicles'wheels in the upper layer of the roadway. The installation must be maintained in accordance with very strict guidelines (the roadway must at all times be sound, clean and intact). The surface tracking zone is relatively small. All of the measurements derived from the identification of vehicular passage are punctual. The coverage of the surface by the vehicles cannot be evaluated. In the case of a waiting line of vehicles, the lack of vehicular presence over the piezoelectric sensor does not enable identification of said waiting line. The measurement is blind. Piezoelectric sensors do not allow for self-diagnostics.
Known as measurement devices are radar and ultrasonic sensors which identify a vehicle by the reflection of an emitted wave. The backscattered wave returns with a frequency shift that allows identification of the direction and the speed of the moving object. The surface tracking zone is relatively small. All of the measurements derived from the identification of vehicular passage are punctual. The coverage of the surface by the vehicles cannot be evaluated. In the case of a waiting line of vehicles, the lack of vehicular presence in the wave field does not enable identification of said waiting line. The measurement is blind.
Known as measurement devices are magnetic sensors which operate by means of an analysis of the variation of the magnetic field of the ground induced by passage of a vehicle. The surface tracking zone is relatively small. All of the measurements derived from the identification of vehicular passage are punctual. The coverage of the surface by the vehicles cannot be evaluated. In the case of a waiting line of vehicles, the lack of vehicular presence on the sensor does not enable identification of said waiting line. The measurement is blind.
Known as measurement devices are video sensors which identify the passage of a vehicle by means of an analysis of the variation in lighting on predefined lines. The surface tracking zone is relatively small. All of the measurements derived from the identification of vehicular passage are punctual. The coverage of the surface by the vehicles is not evaluated.
Regulation of road traffic by means of the signaling of three-color traffic lights comprises using a control unit, called an intersection controller, to control the changes in state of the signals and the duration of the states at the predictable or random demand of the group of users. Certain controllers schedule the green-light time in a cyclical and definitive manner. They do not take into account the demand. Certain controllers schedule the green light signal according to a signaling program selected in relation to the day and time. The signaling program's are contained in memory in a library of programs that have been previously calculated in relation to the traffic measured by magnetic loop type sensors or by direction counting surveys performed manually by monitors. The traffic variations are of two types: the regular predictable variations and the exceptional and random variations. These latter variations can be notable from one day to the next for the same hourly period. Certain controllers are capable of evaluating these variations from the consequences that they generate several minutes later based on the installation of magnetic loops at the entries and exits of each intersection to be regulated. The measurements employed stem from sensors whose surface tracking zone is relatively small. The lack of spatial information means that all of these regulation systems remain blind, such that they are unable to take into account the local and temporal details that influence the congestion and the spatial capacity of the intersection, section and road network. Collection of data based on the flow rate does not allow detection of the regulation and traffic circulation disturbances. Certain cities install cameras in the so-called critical traffic circulation intersections for manual monitoring of the road traffic to supplement information stemming from magnetic loops installed under the road surfaces. Congestion indicators are displayed on a control light panel to attract the attention of the traffic technician who interrupts his tasks in process in order to select the camera corresponding to the intersection and control the display of the images in order to diagnose the type of traffic situation and to manually actuate the controller of the intersection in question.
Video monitoring devices are known which comprise a series of cameras linked to a display panel which has a series of display screens enabling an operator to monitor a certain number of sites entering in the cameras'fields. Such a device allows a single operator to perform monitoring of
Schnader Harrison Segal & Lewis LLP
Tweel John
LandOfFree
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