Patent Publication Number: US-2007103337-A1

Title: Backup traffic control systems and methods

Description:
TECHNICAL FIELD  
      The present invention generally relates to traffic control devices and more specifically to backup traffic control devices.  
     BACKGROUND  
      In the aftermath of major storms, traffic control devices often do not operate because of the loss of electric power to the traffic control devices. This causes confusions on the roadway, adding to the dangers during and after a storm. Often, drivers that approach an intersection with a non-functioning traffic control device are unaware of laws that require the driver to stop at the intersection and treat the non-functioning traffic control device as an all-way stop sign. The resulting confusion can lead to traffic accidents.  
      For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the specification, there is a need in the art for backup traffic control systems and methods.  
     SUMMARY  
      The Embodiments of the present invention provide methods and systems for backup traffic control systems and methods and will be understood by reading and studying the following specification.  
      In one embodiment, a traffic control device is provided. The device comprises a sensing circuit adapted to sense a voltage level of power received from a primary power source and output a low power signal when the voltage level drops below a threshold value; a rechargeable backup power supply adapted to store electrical power; at least one lamp coupled to receive power from the rechargeable backup power supply; at least one switch coupled to switch power between the rechargeable backup power supply and the at least one lamp; and a timer adapted to receive the low power signal and generate a cyclical voltage output based on the low power signal, wherein the at least one switch is adapted to receive the cyclical voltage output and cycle the power between the rechargeable backup power supply and the at least one lamp on and off based on the cyclical voltage output.  
      In another embodiment, a method for controlling traffic at an intersection of two or more roadways is provided. The method comprises sensing a power received from an external power source; when the power received is lower than a threshold value, periodically cycling power from a backup power source to one or more lamps; illuminating the one or more lamps; and controlling traffic based on the one or more lamps.  
      In yet another embodiment, a system for controlling traffic at an intersection of two or more roadways. The system comprises means for storing electric power; means for charging the means for storing electric power; means for sensing a power received from an external power source; means for illumination, the means for illumination powered from the means for storing electric power; means for cycling the means for illumination on and off, the means for cycling responsive to the means for sensing. 
    
    
     DRAWINGS  
      Embodiments of the present invention can be more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the description of the preferred embodiments and the following figures in which:  
       FIG. 1  is a block diagram illustrating a traffic control system of one embodiment of the present invention;  
       FIG. 2  is a block diagram illustrating a rechargeable backup power supply of one embodiment of the present invention;  
       FIG. 3  is a diagram illustrating a timer and switch circuit of one embodiment of the present invention; and  
       FIG. 4  is a flow chart illustrating a method of one embodiment of the present invention. 
    
    
      In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize features relevant to the present invention. Reference characters denote like elements throughout figures and text.  
     DETAILED DESCRIPTION  
      In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of specific illustrative embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense.  
      Embodiments of the present invention provide systems and methods to notify drivers to stop at intersections where the traffic control device has failed due to a loss of electric power. Embodiments of the present invention provide a backup power source and circuitry to implement a blinking red light in one or more directions of an intersection, upon loss of a primary power supply to the traffic control devices.  
       FIG. 1  is a block diagram illustrating a traffic control system  100  of one embodiment of the present invention. System  100  comprises a traffic control device  110  coupled to receive power from a primary power source  105 . In one embodiment, primary power source  105  comprises one of an AC or DC electric power distribution system. In one embodiment, traffic control device  110  comprises a rechargeable backup power source  116  coupled to receive power from one or both of primary power source  105  and a solar panel  114 . Traffic control device  110  further comprises a sensing circuit  112  coupled to monitor power received from primary power supply  105 , a timer  118  coupled to receive a low power signal from sensing circuit  112  and power from rechargeable backup power source  116 , and a switch  120  coupled to receive a flash signal from timer  118 . Traffic control device  110  further comprises at least one lamp  122  coupled to receive switched power from rechargeable backup power source  116  through switch  120 .  
      In one embodiment, during normal operations (i.e. when power is available from primary power source  105 ), lamp  122  receives electric power supplied by primary power source  105  and is controlled by traffic controller  130 . In one embodiment during normal operations, when lamp  122  is a red lamp, traffic controller  130  additionally controls one or more of a green lamp  133  and a yellow lamp  132  in order to control the flow of traffic. In one embodiment, traffic controller  130  includes all the necessary circuitry, including passing of power from primary power source  105 , for the normal operation of lamp  122 , green lamp  133  and yellow lamp  132  to control traffic. In one embodiment, traffic controller  130  is one of any number of systems for controlling standard traffic light signals, as would be appreciated by one skilled in the art upon reading this specification.  
       FIG. 2  illustrates a rechargeable backup power source  116  of one embodiment of the present invention. In one embodiment, rechargeable backup power source  116  comprises at least one battery  117  coupled to a charger  115 . In one embodiment, during normal operations rechargeable backup power source  116  receives power from primary power source  105  to operate battery charger  115 . Battery charger  115  in turn maintains the charge of battery  117 .  
      In one embodiment, sensing circuit  112  monitors the power received by traffic control device  110  from primary power source  105 . In one embodiment, when the voltage of electric power supplied by primary power source  105  drops below a predefined threshold, sensing circuit  112  outputs a low power signal to timer  118 . In one embodiment, sensing circuit  112  comprises a voltage sensing relay, a voltage comparator, or similar power sensing device. Upon receiving the lower power signal, timer  118  cycles switch  120  periodically on and off, allowing current from battery  117  of rechargeable backup power source  115  to periodically flow to lamp  122 . Thus, lamp  122  will appear to drivers as a flashing light. In one embodiment, when lamp  122  is a red lamp, the flashing of lamp  122  notifies drivers approaching the intersection to stop before proceeding. In one embodiment, traffic control device  110  further comprises one or more additional lamps  126  each of which flash on and off as directed by timer  118 . In one embodiment, timer  118  further cycles one or more additional switches  124  on and off, allowing current from battery  117  of rechargeable backup power source  115  to periodically flow and illuminate additional lamps  126 . In an alternate embodiment, additional lamps  126  receive power from rechargeable backup power source  115  via switch  120 .  
      Although this specification uses the term “lamp” to describe lamp  122  and additional lamps  126 , one skilled in the art would readily appreciate that “lamp” is not limited to an incandescent bulb, and encompasses any number of light emitting means now existing or developed in the future. For example, in one embodiment, one or both of lamp  122  and additional lamps  126  comprise one or more of, but not limited to, a neon light and an array of light emitting diodes. In one embodiment, solar panel  114  powers battery charger  115  to maintain the charge of battery  117  while traffic control device  110  operates during a loss of primary power source  105 . In one embodiment, during normal operation, (i.e. when power from of primary power source  105  is available), solar panel  114  powers battery charger  115  to maintain a trickle charge to the rechargeable battery in order to assure proper operation during a power outage.  
      As would be appreciated by one skilled in the art upon reading this specification, there are numerous means to realize timer  118  and switch  120 , of which this specification provides just an example.  FIG. 3  illustrates a timer  118  coupled with a switch  120  of one embodiment of the present invention. In one embodiment, timer  118  is an RC timer comprising a timing device  310 , resistors  320 - 1  (R 1 ) and  320 - 2  (R 2 ), and a capacitor  330  (C) coupled to timing device  310  as shown in  FIG. 3 . In one embodiment, timing device  310  is a 555 timer or similar device. In one embodiment, timing device  310  is powered by rechargeable backup power supply  116 . In one embodiment, time device  310  outputs a cyclical voltage output with a period that is a function of the resistance of resistors  320 - 1  and  320 - 2  and the capacitance of capacitor  330 . In one embodiment, switch  120  comprises a transistor  350  having a source  352  coupled to rechargeable backup power source  115 , a drain  353  coupled to one or both of lamp  120  and additional lamps  126 , and a gate  354  coupled to the output of timing device  310 .  
      In operation, in one embodiment, when timing device  310  receives the low power signal from sensing circuit  112 , timing device  310  outputs a cyclical voltage signal to gate  354  of transistor  350 . In one embodiment, the low power signal comprises a logical high signal from sensing circuit  112 . As the voltage at gate  354  rises, transistor  350  turns on and allows current to flow from battery  117  to one or both of lamp  120  and additional lamps  126 , allowing them to illuminate. As the voltage at gate  354  falls, transistor  350  turns off and interrupts the current flow from battery  117  to one or both of lamp  120  and additional lamps  126 , causing them to darken.  
      In one embodiment one or both of lamp  120  and additional lamps  126  comprise red lamps allowing traffic control device  110  to stop traffic in two or more directions. For example, in one embodiment, when traffic control device  110  controls traffic at a four-way intersection, lamp  120  comprises a red lamp and additional lamps  126  comprise three red lamps so that, upon a loss of primary power source  105 , traffic control device  110  flashes red lamps in all four directions of the intersection. In one embodiment, one or more of lamp  122  and additional lamps  126  comprise at least one yellow lamp. For example, one embodiment, when traffic control device  110  controls traffic at a four-way intersection, upon a loss of primary power source  105 , traffic control device  110  flashes two red lamps in to stop traffic flowing on a first roadway before entering the intersection, and flashes two yellow lamps to caution divers approaching the intersection on a second, intersecting roadway.  
       FIG. 4  is a flow chart illustrating a method for controlling traffic at an intersection of two or more roadways of one embedment of the present invention. In one embodiment, the method begins at  410  with receiving light with a solar panel. The solar panel generates electricity ( 420 ) which is used to charge a backup power source ( 430 ). In one embodiment, the backup power source comprises one or more batteries. The method further comprises sensing a power received from an external power source at  440 . In one embodiment, the external power source provides the electric power required to operate a traffic control device, such as a typical red-yellow-green traffic light. In normal operation, the traffic control device regulates the flow of traffic through the intersection of two or more roadways. When the external power source is not available (e.g. due to loss of power from a storm), traffic control devices not adapted with embodiments of the present invention will go dark. Under these circumstances drivers approaching the intersection must rely on their knowledge of the law to remember that an out of service traffic control device should be regarded as a stop sign. Embodiments of the present invention relieve drivers of that burden by enabling a flashing red light at intersections that have lost external power. In one embodiment, the method proceeds to  450 , when power received from the external power source is lower than a threshold value, and cycles power from the backup power source to one or more lamps, thus illuminating the one or more lamps ( 460 ) in a flashing manner.  
      As would be appreciated by one skilled in the art, the threshold value can be any arbitrary value less than a nominal power level usually provided by the external power source, which would indicate a fault or other instability affecting the supply of power from the external power source. In one embodiment, the threshold value is based on one or both of the voltage and frequency of the power received from the external power source.  
      With the one or more lamps flashing, the flow of traffic approaching the intersection is controlled ( 470 ) by alerting drivers of the need to stop before entering the intersection. In one embodiment, the flashing lamps include at least one red lamp flashing in the direction of traffic on a roadway approaching an intersection to notify drivers to stop before entering the intersection. In one embodiment, the flashing lamps include at least one yellow lamp flashing in the direction of traffic on a roadway approaching an intersection to notify drivers to proceed thought the intersection with caution.  
      As previously discussed above in this specification, there are a number of ways to cycle power from the backup power source to one or more lamps. In one embodiment, cycling power from the backup power source to one or more lamps further comprises generating a cyclical voltage output with a timer. In one embodiment, the timer may be optionally powered from the backup power source. The method then switches power from the backup power source to one or more lamps on and off based on the cyclical voltage output.  
      Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.