Communications: electrical – Vehicle detectors – Speed and overspeed
Reexamination Certificate
1998-07-28
2001-03-20
Swarthout, Brent A. (Department: 2632)
Communications: electrical
Vehicle detectors
Speed and overspeed
C340S905000, C340S907000, C340S917000, C340S933000, C340S943000, C701S117000, C701S119000
Reexamination Certificate
active
06204778
ABSTRACT:
BACKGROUND OF THE INVENTION
(A) Field of the Invention
This invention relates to traffic monitoring systems including warning systems and vehicle ramp advisory systems, for monitoring commercial vehicles.
(B) Description of the Prior Art
Many kinds of systems have been disclosed which monitor and/or control traffic. Typically, each highway department had a command centre that received and integrated a plurality of signals which were transmitted by monitoring systems which were located along the highway. Although different kinds of monitoring systems were used, the most prevalent system employed was a roadway metal detector. In such system, a wire loop was embedded in the roadway and its terminals were connected to detection circuitry that measured the inductance changes in the wire loop. Because the inductance in the wire loop was perturbed by a motor vehicle (which included a quantity of ferromagnetic material) passing over it, the detection circuitry detected when a motor vehicle was over the wire loop. Based on this perturbation, the detection circuity created a binary signal, called a “loop relay signal”, which was transmitted to the command centre of the highway department. The command centre gathered the respective loop relay signals and from these made a determination as to the likelihood of congestion. The use of wire loops was, however, disadvantageous for several reasons.
First, a wire loop system did not detect a motor vehicle unless the motor vehicle included sufficient ferromagnetic material to create a noticeable perturbation in the inductance in the wire loop. Because the trend now is to fabricate motor vehicles with non-ferromagnetic alloys, plastics and composite materials, wire loop systems will increasingly fail to detect the presence of motor vehicles. It is already well known that wire loops often overlook small vehicles. Another disadvantage of wire loop systems was that they were expensive to install and maintain. Installation and repair required that a lane be closed, that the roadway be cut and that the cut be sealed. Often too, harsh weather precluded this operation for several months.
Other, but non-invasive, traffic monitoring systems have also been suggested, among them being the following:
U.S. Pat. No. 3,047,838, patented Jul. 31, 1962 by G. D. Hendricks, provided a traffic cycle length selector which automatically related the duration of a traffic signal cycle to the volume of traffic in the direction of heavier traffic along a thoroughfare. The Hendricks system did not teach the use of electro-acoustic transducers, but instead used pressure-sensitive detectors. While Hendricks employed plural, non-electro-acoustic transducers, the traffic cycle length selector system did not include spatial discrimination circuitry. Hendricks merely described the use of the output of several spatially discriminate detectors to generate a spatially indiscriminate signal.
U.S. Pat. No. 3,233,084, patented Feb. 1, 1996, by H. C. Kendall et al, was directed to a method and apparatus for obtaining traffic data. That invention utilized the output of a vehicle detector as a triggering input to a circuit which then provided an output which was the same for all vehicles. The successive output pulses produced by a succession of vehicles passing the detection point were filtered and averaged so that the resultant signal had its amplitude which was proportional to the number of vehicles passing the detection point in a unit of time.
U.S. Pat. No. 3,275,984, patented Sep. 27, 1966, by J. L. Barker, disclosed a system which detected when traffic was moving too slowly, thereby indicating that a highway was becoming congested, and activated a sign near a highway exit to divert traffic via that exit.
U.S. Pat. No. 3,397,304, patented Aug. 13, 1968, by J. J. Auer, Jr., was directed to a method and apparatus for measuring vehicular traffic. The apparatus measured the traffic parameter of lane occupancy, i.e., the percentage of pavement which was vehicle-occupied. A vehicle presence detector controlled the addition of signals at a constant rate, to a signal accumulating means throughout each vehicle detection interval. At the same time, a signal was being subtracted continually from the signal accumulating means at a rate which was proportional to the present value of the signal which was stored in the signal accumulating means. The magnitude of the stored signal at each moment represented lane occupancy.
U.S. Pat. No. 3,445,637, patented May 20, 1969 by J. M. Auer, Jr., provided apparatus for measuring traffic density in which a sonic detector produced a discrete signal which was inversely proportional only to vehicle speed for each passing vehicle. A meter, which was responsive to the discrete signals, produced a measurement which was representative of traffic density. However, this patent used only a single electro-acoustic transducer for receiving acoustic signals within a detection zone, and did not teach spatial discrimination circuitry for representing acoustic energy emanating from a detection zone.
U.S. Pat. No. 3,544,958, patented Dec. 1, 1970, by L. J. Carey et al, disclosed a system which measured the time taken for a vehicle to traverse the distance between two light beams, and displayed the measured vehicle speed on a warning sign ahead of the vehicle.
U.S. Pat. No. 3,680,043, patented Jul. 25, 1972, by P. Angeloni, disclosed vehicle speed monitoring systems. Such system included posting devices which were positioned at intervals along the highway and which were adapted to receive a speed message from a control station, and to transmit the speed message to passing vehicles in a limited region of the highway in the form of an r-f signal. Each vehicle contained an r-f receiver which was connected to the vehicle speedometer, or other vehicle indication means, in a manner that provided, upon the occurrence of some predetermined excessive speed, an indication to the driver of the vehicle that the speed limit at that particular region of the highway was being exceeded.
U.S. Pat. No. 3,788,201, patented Jan. 29, 1974, by F. Abell, provided a method for establishing vehicle identification, speed and conditions of visibility. The patented method produced a photographic record showing the identification of a moving vehicle, its speed, conditions of visibility, date and time. Conditions of visibility were established by periodically making a first photographic record of a target at a selected location along a highway. In one embodiment, identification and speed were established in a second photographic record by simultaneously photographing a vehicle moving along the highway in the vicinity of the target and a radar speed meter indicating the speed of the photographed vehicle. In a second embodiment, identification and speed were established by taking two pictures with the same photographic means of the identical portion of a moving vehicle in the vicinity of the target at a known time interval in order to make up a second photographic record, and measuring the relative sizes of the image of the identical portion of the vehicle in the two pictures. Thereafter the speed of the vehicle was calculated by interrelating the time interval and vehicle image sizes with the image size of an object in a picture taken by the photographic means located at a known distance from the object. The object had an actual dimension corresponding to an actual dimension of the portion of the moving vehicle appearing in the second photographic record. The first and second embodiments for establishing identification and speed could be combined for purposes of corroborating the speed of the moving vehicle. Date and time were established by simultaneously photographing in all exposures making up the first and second photographic records date and time means showing the date and time at which the exposures are made.
U.S. Pat. No. 3,835,945, patented Sep. 17, 1974, by M. Yamanaka et al provided a device for weighing running vehicles. That device measured the weight of a moving vehicle by measuring either t
Bergan Terry
Klashinsky Rod
International Road Dynamics Inc.
Nixon & Vanderhye P.C.
Swarthout Brent A.
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