Abstract:
An attachment for a traffic signal having a housing for fitting over one of the normal lights, herein the green light, of the signal and overriding the normal sequence in response to preemptive emergency signals, and a electro-optically responsive data display panel on the housing to provide clear and direct instructional messages to motorists as to the appropriate actions to be taken. A first embodiment overrides the normal green light with a reflective electro-optically responsive panel overlying the normal green light to become opaque in response to the emergency signals, with a red light source outside the panel that is activated to produce red reflected light. A second embodiment replaces the normal green (or alternatively yellow or red) signal with a panel of light-emitting elements (LEDs) that have one group capable of providing the normal green signals and a second group that are capable of providing graphic instructions in response to emergency signals. In both embodiments, the display panels provide alternate selections such as “STOP” or a halt symbol as one selection and an arrow or chevron pattern, with “RIGHT” or an abbreviation as a second selection.

Description:
REFERENCE TO PRIOR PROVISIONAL APPLICATIONS 
   This application claims the benefit of prior copending provisional applications Ser. No. 60/380,941, and 60/380,925, both filed May 17, 2002. 

   BACKGROUND OF THE INVENTION 
   This invention relates to traffic signals for controlling traffic flow at intersections of roadways, and relates more particularly to systems that modify traffic signal operation in response to emergency vehicle signals to permit the emergency vehicle to pass quickly and safely through the intersection, and to methods of controlling such signals. 
   Traffic signals have been used for many years to regulate traffic flow at intersections, typically providing a green or “go” light for traffic on one street at preselected intervals while providing traffic on the intersecting street with a red or “stop” light. During the transition from “go” to “stop”, it is customary to provide a yellow or “caution” light for a short interval, warning oncoming motorists to prepare to stop when the red light appears. All three lights often are mounted in a common housing or frame, usually in a vertical row but sometimes horizontally aligned. 
   When an emergency vehicle such as a police car, fire truck or ambulance must pass rapidly through an intersection, the oncoming emergency vehicle typically sounds an audible warning such as a siren and a visual warning such as a flashing light, and then proceeds through the intersection without regard to the existing condition of the traffic signal. For various reasons, these signals are not always sufficient to avoid collisions. Loud noises, closed vehicles with radios or other audio devices playing, and inattentive drivers in some instances lead to dangerous situations in which cross traffic does not stop for the oncoming emergency vehicle, with resulting collisions. 
   A variety of devices have been proposed to allow emergency vehicles to control traffic signals. These typically use radio transmitter systems for activating emergency preemption controls on the traffic signals that will override the normal controls of the signals and provide “stop” signals for cross traffic approaching the intersection and continuous “go” signals for the emergency vehicle. Other special signals have been provided in efforts to provide information to affected drivers regarding the presence and direction of approach of emergency vehicles, whether on intersecting streets or from one direction or the other on the same street. Such systems and devices are well known, and examples are shown in U.S. Pat. Nos. 4,775,865 and 4,704,610 (signs beside traffic signals with vehicle symbols for indicating approaching emergency vehicles); U.S. Pat. No. 6,292,109 (display at corner of intersection with sign shown in  FIG. 6  having arrows indicating the direction of an approaching vehicle, a traffic signal with a siren and a flashing red emergency light); and U.S. Pat. No. 6,362,749 (signal device installed in vehicles and having arrows for indicating the direction of the signal from an approaching emergency vehicle, which also could be installed in an undisclosed manner on a traffic signal). 
   Unfortunately, these prior devices, systems and methods have provided ambiguous and sometimes confusing information and often have been so complex and expensive in construction that they have not been universally installed. Others have been unreliable in operation and have required substantial time and money for maintenance. Accordingly, there has been an ongoing need for an improved and more effective emergency traffic signal device that will overcome the deficiencies of the prior art systems and devices. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention resides in a novel traffic signal device that can be either attached to existing traffic signals or installed in newly constructed signals, and is effective to provide improved visual warning communications to drivers regarding the approach of an emergency vehicle and the actions that are required to avoid the emergency vehicle, and the accompanying method of controlling the traffic signal. For these purposes, a first embodiment of the invention comprises an attachment to the frame or housing of the traffic signal with a special panel that overlies one if the lamps, herein the “green” signal lamp, and is transparent so as to pass the regular light during normal operations, but is electro-optically responsive to an emergency signal to display either a “stop” signal over the regular light, if the emergency vehicle is approaching on a cross street, or a lateral directional movement signal if the vehicle is approaching on the same street. In this manner, traffic not only is warned to stop but also is informed when movement to the side of the roadway is needed. The “stop” signal may be simply a red light superimposed over the regular light of the traffic signal or may be a graphic “halt” or “stop” symbol. 
   A second, preferred embodiment provides an attachment to the existing frame or housing as a replacement for one of the lamps, and substitutes for the regular lamp a combination LED array that can display the normal color signals (green, yellow or red) during normal operation, and, when activated by an emergency signal, will display a selected emergency signal as in the first embodiment. The graphic directional signal also may be a moving “chevron” or arrow directional signal, or also can be a graphic “hand” symbol indicating direction as well. 
   In both embodiments, the method of operation comprises the steps of providing the inventive attachment and then controlling the attachment to provide messages in the novel manner described. 
   Other aspects and advantages of the present invention will be evident from the following drawings, taken in conjunction with the accompanying detailed description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a enlarged fragmentary perspective view showing a portion of an approaching emergency vehicle, not to scale, and a representative traffic signal equipped with an emergency traffic signal device in accordance with a first embodiment of the present invention; 
       FIG. 2  is an enlarged side elevational view of the emergency signal device of  FIG. 1 , partially broken away and shown in cross-section; 
       FIG. 3  is a side elevational view of the electro-optically responsive panel of the emergency signal device of  FIG. 1 ; 
       FIG. 4  is a perspective view similar to  FIG. 1  with a different message on the display panel; 
       FIG. 5  is a perspective view of an improved display device that is a second embodiment of the invention; and 
       FIGS. 6 ,  7  and  8  are front elevational views illustrating alternative arrangements and signals that may be provided with the emergency signal device of the present invention. 
   

   DETAILED DESCRIPTION 
   As shown in the drawings for purposes of illustration, the invention is embodied in an attachment  10  that is mounted on the green or “go” lamp  11  of a conventional traffic signal  12  also having red and yellow lamps  13  and  14 , each comprising a suitable light source (not shown) and an open-ended shroud or shade. A representative emergency vehicle  15  is shown in a position approaching the traffic signal  12  and having a transmitter  17  of a conventional type for actuating the emergency control system. A controller  18  is enclosed in a housing on one side of the signal attachment and receives the transmitted radio signal through an antenna  19 . The controller electronically actuates various features of the invention in response to the radio signals received from emergency vehicles that are travelling on the same street or on an intersecting street. The details of construction, electronics and operation of such controllers in these systems are known, as is indicated in the several patents that are identified in the background of this invention. 
   It has been customary in past systems of this type to enable the emergency vehicles to control the normal, “stop” and “go” signals of the intersection. In addition, some systems sometimes provide signals that indicate the direction of an approaching emergency vehicle and enable drivers of other automobiles, trucks and the like, and even other emergency vehicles, to make decisions as to appropriate evasive actions to avoid interference, or even a collision, with the vehicle that is sending the emergency signal. Typically, as indicated in the cited prior patents, such signals indicate, at most, the direction from which the emergency vehicle is approaching, and leave it to the other drivers to decide what kind of evasive action is appropriate. 
   In accordance with the present invention, the attachment  10  is an improved emergency signal device that provides clear and unambiguous information to drivers as to the specific action or actions needed to avoid the oncoming emergency vehicle. In addition, the improved device is relatively simple and inexpensive in construction and may be economically retrofitted to existing traffic signals as a self-contained unit or provided as an original component of a new traffic signal that is to be installed. 
   For these purposes, the attachment  10  herein is fitted onto one of the three standard lamps  11 ,  13  and  14 , herein the lower or “go” lamp  11  of the signal  12 , and has a special panel  20  forming a lens or cover for the pre-existing lens  21  of the lamp, a special red light source  22 , and a data display panel  23  on one side of the lamp for providing directional information. The attachment  10  is operable when activated to block out the normal green light of the lower lamp  11 , to energize the special red light source  22  which is reflected toward oncoming traffic by the special panel  20 , and to activate the data display panel  23  to provide a selected directional message determined by the controller  18  in response to the directional signal from the emergency vehicle. 
   More specifically, the attachment  10  has a housing that is formed with a tubular upper portion  24  for fitting tightly over the open end of the shade of one of the lamps, herein the lower lamp  11 , as shown in  FIGS. 1 and 2 . The special panel  20  is normally is transparent to the green light and is positioned in front of the regular lens  21 , and the special red light source  22  is a series of red lights, such as red-light emitting diodes (LEDs), that are spaced around the open outer side of the tubular portion of the housing, on the side of the special lens panel  20  opposite the regular lens  21 . 
   The special panel  20  of the first embodiment is constructed in multiple laminated layers, herein three indicated at  20   a ,  20   b  and  20   c  in  FIG. 3 , with the first or outer layer  20   a  having a reflective outside surface but capable of passing light from the regular lamp when the attachment is not activated. Thus, this layer will reflect the red light from the LEDs  30  when the latter are energized. The inside layer  20   b  of the special lens is electro-optically active material that is opaque when activated, thereby to block the normal light from the regular lens  21 . The third layer is transparent and, with the outer layer  20   a , supports the electro-optically active inside layer  20   b.    
   With this arrangement, the normal signals from the green light of the traffic signal can be overridden and converted to a red light to signal that traffic approaching the signal is to stop, regardless of the condition of the normal green lamp  11 . This is the mode to be used when an emergency vehicle is approaching on an intersecting street and all that is needed of the traffic approaching the signal is to stop at the intersection. 
   The data display panel  23  is mounted in the housing on one side of the special panel  20 , typically either below the panel or to one lateral side, and has the capability of enhancing visual communication with drivers. For this purpose, the display panel also is electro-optically active, preferably in the form of an array of selectively energized LEDs covering virtually the entire panel and capable of providing alternating graphic and/or verbal displays on the panel. For example, as shown in  FIG. 1 , one display that is appropriate to accompany the red “stop” signal superimposed over the green lamp is the word “STOP” or the abbreviation “STP” that is shown on the display panel. This augments the signal given by the red light. Alternatively, the panel can be made to display the “halt” graphic symbol that is shown on the panel in the alternative embodiment of FIG.  6 . This symbol is universally recognizable as meaning “do not pass”, as is appropriate when the emergency signal is coming from a vehicle travelling on an intersecting street. 
   For use in controlling traffic signals on the street on which the emergency vehicle is travelling, the graphic signal on the display panel  23  will give directional information such as an arrow pointing toward the right-hand side of the street, to direct traffic toward the curb, as shown in FIG.  4 . This can be coupled with the verbal message “RIGHT”, or an abbreviation such as “RGT”, as shown on the panel in FIG.  4 . Further, for better attention-getting quality, the LEDs in the display panel  18  can be illuminated in a “chevron” pattern, as shown with “RGT” and the arrow symbol in  FIG. 4 , and the “chevron” pattern can be made to appear to move from left to right, through sequential control of the pattern of illumination of the LEDs. Again, this can be accomplished by the controller  18  in a manner that is well known to those skilled in the art. 
   Thus, the first embodiment of the invention comprises an attachment with the ability to override the regular “green” signal of a traffic light with a constant “red” until the emergency vehicle passes, and also with the ability to provide a verbal and/or graphic directional signal ordering drivers either to stop or to pull laterally toward the curb. These two signals typically will be combined, but can be given separately as well. Since this attachment is designed to override the normal green “go” signals, it normally is fitted over the lower lamp  11  of vertically aligned lamps as shown in  FIG. 1 , but also can be placed in other positions as shown in connection with the second embodiment, to be described. 
   It is to be understood that the antenna  19  is connected by electrical circuitry (not shown) to the controller  18  inside the attachment housing, only the switch panel  25  of the controller being exposed in  FIGS. 1 ,  2  and  4 . A compass or other directional instrument  26  is shown on the attachment to assist in orienting the attachment and the controller should directional information be required. The controller has the capability of determining the direction from which a detected signal is coming, thus determining the appropriate actions to be initiated for the signal device. 
   In addition, the invention is illustrated by a second attachment  35  (FIGS.  5 - 8 ), in which a special lamp panel  37  of the general type shown in the first embodiment at  20  provides graphic directional signals as well as color signals to instruct motorists regarding necessary actions. This panel is electro-optically responsive to signals from approaching emergency vehicles to produce either a “stop” signal or a directional signal such as a moving “chevron” pattern directing the motorist toward the curb. In the U.S., this will be the right-hand side as shown in  FIG. 5. A  graphic “hand” design pointing to the right (not shown) may be provided instead of, or in combination with, such a “chevron” symbol for additional attention-getting impact and communication. To provide these features of operation, the special panel  27  of the alternative attachment  35  is formed as a flat array of LEDs capable of producing contrasting patterns, such as red on a dark background and at least one solid pattern, such as green or yellow, and the controller indicated generally at  38 , as in  FIGS. 1 and 2 , is programmable in a manner well known in the electro-optical arts to produce the desired color or graphic pattern on command. Thus, in the normal operating condition of the traffic signal equipped with the attachment  35  (as a total replacement for the normal lamp), the lamp panel  37  produces the regular signal in the proper sequence, green-colored if the attachment is mounted in the lower, “go” position at  11  as shown in  FIG. 6  or yellow-colored if the attachment is mounted in the central “caution” position at  13  as shown in FIG.  7 . LEDs of the appropriate color are energized by the controller  25  in the proper regular sequence. In such normal operation, the special display panel indicated generally at  39  can be left blank. 
   When the controller  38  receives an emergency signal, however, the special lamp panel  37  is energized by the controller  38  to produce the selected graphic and color signals and to terminate the normal color display, as appropriate. For example, when the emergency signal is received from a vehicle travelling in either direction on the same street as the receiving vehicle, the chevron signal shown in  FIG. 5  is activated, along with the “RGT” and chevron graphic display shown in FIG.  5 . The chevron symbols may be sequentially controlled for even greater impact and clearer meaning. This also is illustrated in different lamp positions in  FIGS. 7 and 8 . 
   If the emergency signal is received from an emergency vehicle approaching the intersection on the intersecting street, the controller  38  activates the lamp panel  37  and the data panel  39  in a different manner, because movement of vehicles toward the curb is not the desired response. The controller produces a red, or “stop” signal by activating red light-emitting LEDs in the lamp panel  37 , with the accompanying graphic instructional display on a data panel  39 . 
   As an incidental benefit of the presence of the data panel on the traffic light, it is possible to program the controller to receive and display emergency messages of different kinds, such as the well known “Amber Alert” messages. The only limitation in this respect is the size and available space of the data panel, since compactness is a desirable feature. 
   Accordingly, it will be seen that the invention provides greatly improved directions to motorists in response to the preemptive traffic control signals from approaching emergency vehicles, with an attachment that can be retrofitted to an existing traffic signal in a simple and relatively inexpensive manner to perform the steps of the method of the invention. It also will be evident that the embodiments disclosed are merely illustrative of the invention and that various modifications and changes may be made within the scope of the invention.