Communications: electrical – Traffic control indicator – Plural intersections under common central station control
Reexamination Certificate
2002-03-29
2004-08-24
Pham, Toan N. (Department: 2632)
Communications: electrical
Traffic control indicator
Plural intersections under common central station control
C340S933000, C340S934000, C701S118000
Reexamination Certificate
active
06781523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a monitoring system for vehicular traffic on roads, and more specifically to a road traffic monitoring system that monitors monitoring areas consisting of ordinary roads, intersections between them, entrances to and exits from expressways, and connectors between expressways, or namely strategic traffic areas where three or more entrances or exits intersect, that is effective in monitoring the vehicular traffic situation at these monitoring areas, that determines the vehicular traffic situation in real time, that measures and monitors the vehicular traffic situation by time zone, day and month, and by season throughout the year, and that when combined with statistical processing functions, contributes to optimal traffic control and effective utilization of the road traffic network.
2. Description of the Prior Art
Conventional vehicular traffic survey methods and road traffic monitoring methods include methods involving the counting of the number of passing cars by survey personnel stationed at intersections or the like, as well as automatic measurement methods such as ultrasonic-based measurement methods, magnetic detector-based measurement methods, and methods wherein the vehicle types, number of vehicles and the like are measured using image recognition technology from image signals obtained from television cameras. This information is used to provide road traffic condition information and for road traffic control.
Examples of ultrasonic-based measurement methods include the vehicle trip time measurement disclosed in the Publication of Examined Japanese Patent Application JP-B-7-104998 and the vehicle type determination method disclosed in Japanese Patent No. 2596554.
FIG. 10
is an explanatory diagram showing an example of the construction of a road traffic monitoring system that uses known ultrasonic technology. Here, an ultrasonic transceiver
26
installed above the road emits ultrasonic, and the ultrasonic reflected from the road surface or vehicle
27
is received by the ultrasonic transceiver
26
installed above the same road. The roundtrip time from emission until the reflected wave was received is measured and compared against the time required for a wave reflected from the road to arrive, stored in advance as data. A judgment is made as to whether or not a vehicle is passing upon the road, and if a vehicle is determined to be passing, then the height of the vehicle
27
is calculated from the time for the reflected wave to arrive, thereby determining the type of vehicle. In addition, this scheme is such that the vehicle height data is measured based on the transmission spacing of the transmitted signal, and thus the vehicle type is determined to be either a small vehicle or large vehicle.
In addition, examples of magnetic sensor-based measurement methods include the vehicle detection sensor and traffic flow measurement system disclosed in Japanese Patent No. 2729977 and the vehicle type determination method disclosed in Japanese Patent No. 2709995. In these methods which use magnetic sensors, a plurality of magnetic sensors installed upon the road detect the magnetic characteristics of a vehicle, and the passage of a vehicle is determined if the difference between a pair of maxima and minima in the magnetic data present during a fixed period of time is above a fixed value. The type of vehicle is determined by the magnitude of the difference, its direction of travel is determined from the advancement or retardation of the detected phase difference, while its speed is calculated from the magnitude of the phase difference.
FIG. 11
is an explanatory diagram showing the concept of road traffic monitoring technology using a known optical reading device. In this case, a constitution that uses an optical reading device
24
for optical photography installed above the lane and an image processor
28
is adopted. In a scheme for road traffic monitoring, the image processor
28
extracts an image of the license plate portion from the image of the photographed vehicle
27
, character recognition is performed on the extracted image and the license plate information is used as vehicle-number data. Thus, the determination of the vehicle type and position can be performed by the optical reading device
24
(Publication of Examined Japanese Patent Application JP-B-06-070833), while the travel time of a vehicle passing between several points can be determined by comparison with the results of detection at other points (Japanese Patent No. 2965714). To wit, by means of the system shown in the present diagram, it is possible to measure the time required for an identified vehicle to travel and also monitor the traffic situation.
However, among the aforementioned vehicular traffic survey methods and road traffic monitoring methods, methods involving the counting of the number of passing cars by the visual observation of survey personnel become work in which people are directly involved, so they are inappropriate for constant surveys or monitoring. In addition, among the aforementioned automatic measurement methods related to road traffic monitoring, the ultrasonic-based measurement methods are schemes wherein ultrasonic emitted from an ultrasonic transceiver installed above the road is reflected from the road surface or vehicle and received, so it has drawbacks in that it is difficult to determine the type of vehicle other than how large it is, and depending on the situation of vehicle flow, errors in the count may easily occur. In addition, while schemes wherein a magnetic detector installed above the road detects the magnetic characteristics of vehicles can offer high reliability in the count of the number of passing vehicles, determination of the type of vehicle is difficult, in the same manner as in the case of an ultrasonic scheme, and it is difficult to survey or monitor the overall flow of vehicles especially at intersections where vehicles can go straight or turn left or right. Moreover, in road traffic monitoring schemes using television cameras, while it is possible to recognize and record an image of the situation of congestion from the photographed images, there are many unsolved problems regarding quantitative analysis and statistical processing. Furthermore, in a scheme wherein the passing vehicles traveling upon a road are photographed, the license plates are extracted from the image data and character recognition is performed so that the license plate information is used as vehicle-number data in a scheme using image recognition to monitor the traffic situation, while this has the possibility of permitting various types of statistical monitoring to be performed regarding the traffic flow situation, in the current state, image processing takes too much time so it is difficult to perform traffic monitoring on all traveling vehicles.
Separate from the prior art as described above, a vehicular monitoring method for road traffic using radio waves has been proposed as a scheme wherein transmission signals are output from a transceiver installed at one end of a leaky coaxial cable, the waves reflected from a target object are received and thus the position of the vehicle is detected by a vehicle-position detector (Japanese Patent No. 2981888).
However, while the constitution consisting of a leaky coaxial cable laid along the road and a transceiver installed at one end thereof is effective as one technique for capturing the movement of vehicles upon a road, as a road traffic monitoring technique, the determination of the type of vehicle is difficult, and count errors easily occur depending on the situation of the flow of vehicles on a multi-lane road, so this has drawbacks similar to those of other schemes.
On the other hand, transponder schemes wherein the simultaneous determination of positions of aircraft by radar and the triggering of automatic responses of unique identification numbers that identify aircraft serve important roles in aircraft control systems. The Publication of Unexamined Japa
Kobayashi Akira
Matsui Toshiaki
Yuzawa Harunobu
National Institute of Information and Communications Technology
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pham Toan N.
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