(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 the wheel load or axle load. It avoided inaccuracies due to vibration through the use of means for producing two signals which were proportioned to the downward force on the near and far edges of a platform as the wheel or wheels passed over it. It then averaged the weight for a period which was initiated when the ratio of the signals had a first value and terminated when the ratio of the signals had a second value.
U.S. Pat. No. 3,920,967, patented Nov. 18, 1975, by D. T. Martin et al, provided a computerized traffic control apparatus for controlling the flow of vehicular traffic through a network of intersections. Detectors in proximity to selected intersections generated electrical signals which were representative of the commencement and termination of vehicle presence. One or more field preprocessor received these signals and responsively generated secondary signals which were representative of vehicle count and speed. These secondary signals were transmitted to a computer which analyzed them and responsively generated control signals which were transmitted to, and governed, the sequential operation of traffic signal heads at controlled intersections.
U.S. Pat. No. 3,927,389, patented Dec. 16, 1975, by V. Neeloff, disclosed a system which counted the number of axles on a vehicle to enable classification of the vehicle and the calculation of an appropriate tariff for use of a toll road.
U.S. Pat. No. 3,983,531, patented Sep. 28, 1976, by T. B. Corrigan, disclosed a system, which measured the time taken for a vehicle to pass between two loop detectors and operated a visual or audible signal if the vehicle exceeded a set speed limit.
U.S. Pat. No. 4,049,069, patented Sep. 20, 1977, by R. Tamarura et al, provided a device for weighing running vehicles. That apparatus included a series of platforms with the length of each platform being shorter than the distance between axles. Means were provided for converting displacement of the platforms to electrical signals. Electronic means were provided for averaging the signals which were produced by the individual axle loads to produce the weight of the vehicle.
U.S. Pat. No. 4,163,283, patented Jul. 31, 1978, by R. A. Darby, provided an automated method to identify aircraft type. In that invention, two sensors were spaced at a known separation to produce signal pulses when activated by the wheels of a taxiing aircraft. The signals were transmitted to a processor in which the wheelbase of the aircraft could readily be calculated. Since specific aircraft types have unique wheelbase dimensions and characteristics, the type of aircraft passing the sensors was determined in a processor. Also, the time, direction, and speed of the aircraft were determined and logged by the processor.
U.S. Pat. No. 4,250,483, patented Feb. 10, 1981, by A. C. Rubner, provided a system for signalized intersection control. The patented coordinated traffic signal control system included a plurality of signalized intersections with controllers including coordination means to relate cycle timing between intersections without dedicated interconnecting communication channels. Coordination means including radio receiver tuned to receive broadcast standard time, cycle timers related to data from broadcast time after iterative broadcast data check, signal cycle program selection from a plurality of programmable signal cycle program data inputs with cycle length and offset selection through time of day or traffic count program outputs. Such a system provided fixed cycle timing relationship with other similarly equipped intersections that responded to anticipated or detected changes in traffic patterns.
U.S. Pat. No. 4,251,797, patented Feb. 17, 1981, by P. Bragas et al, provided a vehicular direction guidance system, particularly for interchange of information between road mounted units and vehicle mounted equipment. In that system, a circuit was provided to detect the direction of movement of the vehicle with respect to a fixed road-mounted loop, which could then extend over opposing lanes of a highway network. The direction detecting equipment was mounted either on the vehicle, or was connected to the road mounted unit so that correct destination guidance information could be transmitted to vehicles passing a loop which was embedded in the roadway upon transmitting from the vehicle to the roadway a target or destination code.
U.S. Pat. No. 4,284,971, patented Aug. 18, 1981, by E. G. Lowry et al, provided an overheight vehicle detection and warning system. The patented system was for alerting drivers of vehicles which had an overall height which was too great to clear an overhead obstruction in their path. Respective pairs of cooperating light sources and light sensors were spaced at appropriate distances from each other and in advance of the overhead structure, with the light beam from each light source being directed to the corresponding light sensor with which such light source was paired. The respective light beans were momentarily interrupted or broken as a vehicle having an excessive overall height passed the successive pairs of light sources and light sensors. When the light beams had been broken in sequence and within a preset, given time period, a signal was sent to the control station which, in turn, activated a visible, flashing, electric sign indicating that the approaching vehicle was too high to clear the obstruction, and warning the driver of the vehicle to stop or exit from the thoroughfare. If the light beams were not broken in sequence within the preset time period, the system automatically cleared and reset itself to ready status. A message of the overheight vehicle could be transmitted to the proper highway authorities simultaneously with the activation of the warning sign. A mechanical sensor could be located on the overhead structure, with an associated camera to take a picture of the vehicle if the driver failed to stop and collision with the overhead structure occured. A collision message could also be transmitted to proper highway authorities.
U.S. Pat. No. 4,560,016, patented Dec. 24, 1985, by P. Ibanez et al, provided a method and apparatus for calculating the weight of a vehicle while it is in motion. An optical fiber was embedded into a matrix and a multiplicity of microbending fixtures were distributed along the path of the optic fiber. Then, as the wheels of a vehicle passed over the pad, the force of the wheels caused the microbending fixtures over which they passed to pinch together and attenuate the light which was transmitted through the optic fiber. The light which was transmitted through the optic fiber from a light source at one end of the optic fiber was received by a light receiver at the other end of the optic fiber. Then, by measuring the amount of light input and the net amount of light output, and calibrating the device, the weight of each axle and the weight of the vehicle above that axle was measured. By successively measuring the weight of each such axle and its associated portion of the vehicle as it passed over the pad, the combined weight of the axles were linearly added together to arrive at the total weight of the vehicle.
U.S. Pat. No. 4,591,823, patented May 27, 1986, by G. T. Horvat, disclosed a complicated system using radio transceivers which were located along the roadway which broadcast speed limit signals by transceivers carried by passing vehicles. Signals returned by the vehicle mounted transceivers enabled the roadside transceivers to detect speed-violations and to report them to a central processor via modem or radio.
U.S. Pat. No. 4,727,371, patented Feb. 23, 1988, by R. M. Wulkowicz, provided a traffic control system and devices for alleviating traffic flow problems at roadway junction. Such system included a first detector for detecting the position of a first vehicle along a first vehicle path. The system included a dynamic roadway sign for displaying the junction, the vehicle paths and the relative position of the first vehicle to the junction. The dynamic roadway sign was positioned along a second vehicle path, to be visible to any vehicles on the second vehicle path approaching the junction. The dynamic roadway sign was positioned sufficiently prior to the junction to allow sufficient time for vehicles travelling on the second vehicle path to act without abrupt manuevers to avoid collision with the first vehicle at the junction. The dynamic roadway sign included a graphic display of the junction for the vehicle paths, and icons which were positioned in sequence in one of the vehicle paths. Each of the icons were illuminated to indicate the presence of a vehicle at a pre-determined position on the vehicle path and its relative position to the junction.
U.S. Pat. No. 4,750,129, patented Jun. 7, 1988, by J. Hemstmengel et al, was directed to the production of an alarm signal on the basis of data obtained only from the speed of a vehicle which had actually overtaken a slower vehicle. Consequently, speed-limited signals were only produced by signal display arrangements to warn the overtaking vehicle if there was a real risk of a collision.
U.S. Pat. No. 4,789,941, patented Dec. 6, 1985, by B. Nunberg, provided a computerized ultrasonic vehicle classification system. That system was adapted for classification of vehicular traffic, as at a toll collection booth. An ultrasonic ranging unit was mounted above the traffic lane, facing downward. The unit was activated by the presence of a vehicle and proceeded to measure repetitively the momentary vertical distance of the vehicle from the ranging unit. Processing circuitry was provided to ascertain average and maximum height, rejecting aberrational readings. The computerized system included a "look-up" of standard vehicular categories, enabling classification of vehicles by comparison of the data received with pre-programmed standard categories.
U.S. Pat. No. 4,793,429, patented Dec. 27, 1988, by R. J. Bratton et al, provided a dynamic vehicle-weighing system. In that system, one or more piezoelectric weight sensors produced charge outputs in response to the weight of a vehicle passing over the sensors. A charge amplifier converted the sensor outputs to a voltage level. A peak voltage detector detected the peak voltage, which represented the sum of all sensor outputs. The peak voltage was then converted to a weight value using the thickness sensitivity of the piezoelectric material.
U.S. Pat. No. 4,806,931, patented Feb. 21, 1985, by T. M. Nelson, provided a sound pattern discrimination system. The patented system was provided for the detection and recognition of pre-established sound patterns, e.g., the various patterns produced by the sirens of emergency vehicles. The system included a microprocessor which was programmed with pre-established sequence detection algorithms corresponding to the different types of emergency vehicles sirens signal patterns which were to be recognized. A first omnidirectional microphone was coupled thorough a bandpass circuit to a trigger circuit to produce square wave signals which were representative of analog signals in the band of interest. At least two directional microphones were coupled through similar bandpass amplifier circuits to analog digital converters which produced a digital output which was representative of the strength of the signals which were received by the directional microphones. This directional information along with the output of a Schmitt trigger, was supplied to the microprocessor which was used to control the signal lights at an intersection in response to the detected siren.
U.S. Pat. No. 4,908,616, patented Mar. 13, 1990, by J. P. Walker, disclosed a simple system to operate regular traffic signals or warning signs which were deployed at a traffic-signal-controlled intersection. A warning device was positioned in the approach to the intersection at a "reaction point" and gave an indication to a driver as to whether or not that vehicle was too close to the intersection to stop safely if the traffic signal had just changed. The system did not measure vehicle speed and could account for differing stopping distances for different classes of vehicle.
U.S. Pat. No. 5,008,666, patented Apr. 16, 1991, by F. J. Gebert et al., disclosed traffic measurement equipment employing a pair of coaxial cables and a presence detector for providing measurements including vehicle count, vehicle length, vehicle time of arrival, vehicle speed, number of axles per vehicle, axle distance per vehicle, vehicle gap, headway and axle weights.
U.S. Pat. No. 5,060,206, patented Oct. 22, 1991 by F. C. de Metz Sr., provided a marine acoustic detector for use in identifying a characteristic airborne sound pressure field which was generated by a propeller-driven aircraft. The detector included a surface-buoyed resonator chamber which was tuned to the narrow frequency band of the airborne sound pressure field and which had a dimensioned opening which was formed into a first endplate of the chamber for admitting the airborne sound pressure field. Mounted within the resonator chamber was a transducer circuit comprising a microphone and a preamplifier. The microphone functioned to detect the resonating sound pressure field within the chamber and to convert the resonating sound waves into an electrical signal. The pre-amplifier functioned to amplify the electrical signal for transmission via a cable to an underwater or surface marine vehicle to undergo signal processing. The sound amplification properties of the resonator air chamber were exploited in the passive detection of propeller-driven aircraft at airborne ranges exceeding those ranges of visual or sonar detection to provide 44 dB of received sound amplification at common aircraft frequencies below 100 Hz. 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. 5,109,224, patented Apr. 28, 1992, by D. Lundberg, provided a road traffic signalling system. The patented system was for signalling individually to a vehicle driver in a flow of traffic that he was too close in relation to his speed to the vehicle ahead. The system comprises a succession of interconnected electronic signalling units of the "cat's eye" type which were positioned at intervals along the road. Each signalling unit detected and timed the passage of vehicles past the unit, determined the distance to the vehicle ahead and communicated with adjacent units. Signalling to the driver may be direct by light signals emitted from units in front of his vehicle, or indirect by transmitting a local signal from each unit for detection by vehicle-borne receivers. The Lundberg sensors merely detected vehicle presence and the processor, using the distance between sensors, then computed the speed of the vehicle. Lundberg's system detected the speeds both of a lead vehicle and a following vehicle and used "pre-programmed rules" to determine whether or not the following vehicle was too close for its speed. If it was, the processor lighted up the cat's eyes in the road ahead to warn the driver of the following vehicle to slow down. The maximum safe speed was obtained from a table which listed several different maximum speeds for different weather conditions. Lundberg's system merely selected a maximum speed from that table regardless of the type of vehicle.
U.S. Pat. No. 5,146,219, patented Sep. 8, 1992, by W. Zechnall, provided a device for the output of safety-related road information in locating and navigating systems of land vehicles. The patented information output device was for a computerized locating and navigating system of motor vehicles which, in addition to stored geographical data of an electronic road map, delivered safety-related information concerning determined sections of road. The information was stored and given out, e.g., optically or acoustically, when reaching the sections of road.
U.S. Pat. No. 5,231,393, patented Jul. 27, 1993, by B. F. Strickland, provided a mobile speed awareness device. That speed awareness device allowed passing traffic to perceive their true speed from a source other than their own speedometers. A trailer supported a container within which a radar source was contained and was operatively connected to a display panel. A suitable source of power operated the radar and display and included a battery, an optional photo voltaic source to power the battery and a plurality of instrumentalities to preclude or render less likely that the trailer will be moved by unauthorized personnel. These instrumentalities included a removable trailer hitch, an axle lock, support stands for elevating the trailer and an internal alarm system.
U.S. Pat. No. 5,250,946, patented Oct. 5, 1993, by D. Stanzcyk, provided a device for estimating the behaviour of crowd users. In that device, each person was the driver of a moving body. The device measured the average speeds of a same group or more generally of different groups in one location or at different locations. The device included a casing which was concealable inside an envelope which included a display unit which was programmable by the threshold of the selected speed, and alternatively, two counters, one indicating the number of moving bodies exceeding the threshold value and the other counter indicating the total number of moving bodies. The components included a Doppler sensor, an amplification stage, a logic stage for the control of the counters, and a power source (i.e., batteries). The device and method for the measurement of average speeds of road users was used in relation to traffic security, and to the measurement of instantaneous speeds, of lengths of the bodies and to their classification in relation to rolling bodies on roads.
U.S. Pat. No. 5,315,295, patented May 24, 1994, by Y. Fujii provided a vehicle speed control system. The patented vehicle speed control system was used, with a vehicle navigation system, for indicating a location of the vehicle on a road map as the vehicle traveled and for providing information related to the road, including curves of the road. The vehicle speed control system received information which was related to curves of a road on which the vehicle navigation system indicated that the vehicle location was before the curve. The system calculated a limit vehicle speed, at which the vehicle can negotiate and pass safely through the curve, based on the vehicle speed and the radius of curvature of the curve. When the vehicle speed was higher than the limit vehicle speed, the vehicle speed control system provided a warning and/or automatically braked the vehicle, or automatically closed a throttle of the vehicle, so as to lower cause the vehicle speed to fall below the limit vehicle speed.
The known systems did not, however, deal with the fact that a particular site will not be a hazard for one type of vehicle, for example an automobile, but will be a hazard for a truck. When commercial vehicles, especially large trucks, are involved in accidents, the results are often tragic. Statistics show that, although commercial vehicles are involved in a relatively small percentage of all motor vehicle accidents, they are involved in a higher percentage of fatal accidents than other vehicles. Consequently, they warrant special monitoring.
U.S. Pat. No. 5,617,086, patented Apr. 1, 1997, by R. Klashinsky et al, and assigned to International Road Dynamics Inc., provided an improved traffic monitoring system which was especially suited to monitoring commercial vehicles. That invention was concerned with assessing whether or not the site constituted a hazard for a particular vehicle depending upon its size, weight, speed and the like. The essence of that invention was to use a variable parameter (vehicle speed) and a fixed parameter (vehicle weight) to provide information relative to the maximum speed at which a hazard may be safely negotiated based upon the site-specific data of that hazard.
That invention was therefore concerned with the fact that a hazard (e.g., a particular curve, incline, controlled intersection, or the like) will not be a hazard for one type of vehicle, for example an automobile, travelling at a particular speed, but will be a hazard for another type of vehicle, for example, a truck travelling at the same speed. Recognizing this, that system had sensors to measure the weight and, if desired, one or more other physical parameters of the vehicle, e.g., height, number of axles or the like, and a processor for storing data specific to the site, e.g., severity of an incline, curvature and camber of a bend, or distance from the sensors to a controlled intersection.
The processor used both the particular vehicle data and the site-specific data to compute a maximum speed for that particular vehicle safely to negotiate that particular hazard. In essence, therefore, the system used the weight and, if desired, one or other more of the physical parameters of the vehicle to assess the forward momentum of that vehicle and to determine whether or not that vehicle can negotiate the hazard safely.
Several different embodiments of that invention were taught. One embodiment of that invention was directed to a traffic monitoring system which included a set of sensors which were disposed in a traffic lane approaching a hazard for providing signals which were indicative of the speed, and also indicative of at least the weight of a vehicle traversing the set of sensors. A processor had a memory for storing site-specific dimensional data related both to the hazard and to signals from the set of sensors. A traffic signalling device was associated with the traffic lane and was disposed downstream of the set of sensors, the traffic signalling device being controlled by the processor. The processor was responsive to the signals from the set of sensors for computing the actual vehicle speed. The processor also computed a maximum safe vehicle speed, which was derived from the site-specific dimensional data and from at least the weight of the vehicle. The computed maximum vehicle safe speed was thus the maximum speed for the vehicle safely to negotiate the hazard. The computed actual vehicle speed was compared with the computed maximum safe vehicle speed. The traffic signalling device was then operated if the computed actual vehicle speed exceeded the computed maximum safe vehicle speed.
Another embodiment of that invention was a traffic monitoring system for use in association with a traffic-signal-controlled intersection having a set of traffic signals and a traffic signal controller. The system included a plurality of sensors which was disposed in a traffic lane upstream of the traffic-signal-controlled intersection. The plurality of sensors included a final sensor which was disposed a predetermined distance in advance of the intersection, a preceding sensor which was disposed a predetermined distance preceding a final sensor in the direction of traffic flow, and a further sensor which sensed weight of the vehicle for providing signals indicative of the weight of the vehicle. A processor was included which had a memory for storing site-specific dimensional data including the predetermined distance. The processor was responsive to signals from the vehicle weight sensor, from the preceding sensor, and from the final sensor to compute a predicted vehicle speed at the final sensor. From the site-specific dimensional data, the processor then determined whether or not the predicted vehicle speed exceeded a computed maximum speed, at which speed the vehicle can safely stop at the intersection, should the traffic signals require it. If the vehicle cannot safely stop at the intersection, the processor transmitted a pre-emption signal to the traffic signal controller, thereby causing the traffic signal controller to switch, or to maintain, the traffic signal to afford right-of-way through the intersection to that vehicle.
Yet another embodiment of that invention provided a traffic monitoring system for determining potential rollover of a vehicle, The sensor comprised a set of sensor arrays which was disposed in a traffic lane approaching a curve and a vehicle height sensor. The site-specific data included characteristics of the curve, e.g., camber and curvature. The traffic signal device included a variable message sign which was associated with the traffic lane and which was disposed between the sensor arrays and the curve. The processor was responsive to the signals from the sensor array for computing, as the vehicle speed, a predicted speed at which the vehicle will be travelling on arrival at the curve, and derived a maximum safe speed for the particular vehicle to negotiate the curve safely on the basis of vehicle parameters, including weight and height. The processor compared the predicted speed with the maximum speed and operated the traffic signal to display a warning to the driver of the vehicle if the predicted speed exceeded the maximum safe speed. Such a system could be deployed, for example, at the beginning of an exit road from a highway, between the highway exit and a curved exit ramp, and would warn the driver of a tall vehicle was travelling so quickly that there would be a risk of rollover as it attempted to negotiate the curve. In such embodiment of that invention, it was necessary also to measure the height of the vehicle as it approached a curve, since the lateral momentum of the vehicle in the curve can be predicted to determine the safe speed at which the vehicle can negotiate the curve without rollover. Thus, the system of that invention computed a safe maximum speed for a particular vehicle in dependence upon, among other things, the weight and height of the vehicle.
Thus, the following systems have now been provided:
A truck rollover advisory system, which is a system designed to reduce truck rollover accidents which occur on highway exit ramps, in which in-road and off-road sensors determine individual truck speed, weight, height and type. From this real time data/information, the probability of a particular truck rolling over is computed by a controller. A warning sign is automatically activated if an unsafe configuration is detected.
A downhill truck speed advisory system, which is a variable message sign to advise individual trucks of a safe descent speed prior to beginning a long downhill grade, in which, as trucks approach the downhill grade, a controller computes individual truck weight and configuration and determines the maximum safe descent speed for that particular truck using FHWA (Federal Highway Administration) guidelines. A variable message sign displays the safe descent speed for individual trucks.
A runaway truck signal control system, which reduces the possibility of disastrous intersection accidents resulting from a runaway truck. As trucks proceed down a slope, the speed, weight and classification of each individual truck is determined. If the truck is travelling too fast to stop safely at the intersection downstream, a signal will be transmitted from a controller to the traffic signal lights. The lights will either hold or change to green until the oncoming truck travels through the intersection.