Patent Publication Number: US-2023141273-A1

Title: Network-based vehicle traffic signal control system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/105,292, entitled “NETWORK-BASED VEHICLE TRAFFIC SIGNAL CONTROL SYSTEM” and filed on Nov. 25, 2020, soon to issue as U.S. Pat. No. 11,367,350, which is a continuation of U.S. patent application Ser. No. 16/685,929, entitled “NETWORK-BASED VEHICLE TRAFFIC SIGNAL CONTROL SYSTEM” and filed on Nov. 15, 2019, issued as U.S. Pat. No. 10,854,074, which is a continuation of U.S. patent application Ser. No. 15/976,402, entitled “NETWORK-BASED VEHICLE TRAFFIC SIGNAL CONTROL SYSTEM” and filed on May 10, 2018, issued as U.S. Pat. No. 10,482,763, which are hereby incorporated by reference herein in their entireties. Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 
    
    
     BACKGROUND 
     Light heads at a street intersection generally each include various lights, such as one or more red lights, one or more yellow lights, one or more green lights, one or more turn signal lights, etc. A typical vehicle traffic signal control system includes a control box located near an intersection at which one or more light heads are located. The control box typically includes components for controlling which lights of the light head(s) are enabled and which lights of the light head(s) are disabled. For example, the control box may include a controller, a power distribution module, relays, and a conflict monitor. 
     SUMMARY 
     The systems and methods described herein each have several aspects, no single one of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure, several non-limiting features will now be discussed briefly. 
     One aspect of the disclosure provides a system comprising a traffic control box comprising a controller; and a first light head. The first light head comprises a processor, a first red light, and a first green light, where the first light head is coupled to the controller via a wired connection and is configured to receive electrical power from the controller, and where the processor is configured with computer-executable instructions that, when executed, cause the processor to at least: process a light head control message received from the controller; process a first status message received from a second light head via the controller, where the first status message indicates that a second green light is off; process a second status message received from the second light head via the controller, where the second status message indicates that a second red light is on; in response to reception of the second status message, determine that the first green light can be activated based on the light head control message; cause the electrical power received from the controller to pass through to the first green light to cause illumination of the first green light; generate a third status message indicating that the first green light is on; and transmit the third status message to the second light head via the controller. 
     The system of the preceding paragraph can include any sub-combination of the following features: where the system further comprises a crosswalk button coupled to the controller, where the crosswalk button, when activated, causes a crosswalk sign to signal that pedestrians can cross an intersection in a first direction, and where the first light head faces a second direction that is perpendicular to the first direction; where the computer-executable instructions, when executed, further cause the processor to at least: process a fourth status message received from the crosswalk button via the controller, where the fourth status message indicates that the crosswalk sign is disabled, and in response to reception of the second and fourth status messages, determine that the first green light can be activated based on the light head control message; where the system further comprises a crosswalk button coupled to the controller, where the crosswalk button, when activated, causes a crosswalk sign to signal that pedestrians can cross an intersection in a first direction, and where the first light head faces the first direction; where the light head control message comprises an indication that the first green light is deactivated a threshold period of time after being activated, and where the computer-executable instructions, when executed, further cause the processor to at least: process a fourth status message received from the crosswalk button via the controller, where the fourth status message indicates that the crosswalk sign is enabled, determine that the threshold period of time has expired, determine that no status message indicating that the crosswalk sign is disabled has been received from the crosswalk button after reception of the fourth status message, and determine not to deactivate the first green light; where the computer-executable instructions, when executed, further cause the processor to at least: process a fifth status message received from the crosswalk button via the controller, where the fifth status message indicates that the crosswalk sign is disabled, and cause the electrical power received from the controller to no longer pass through to the first green light to deactivate the first green light; where the light head control message comprises one or more rules defining a condition under which the first light head can activate the first green light; where the first light head is coupled to the controller via an Ethernet cable; where the first light head is configured to receive the electrical power from the controller via the Ethernet cable; and where the system further comprises a vehicle sensor coupled to the controller, where the vehicle sensor is configured to receive the electrical power from the controller via an Ethernet cable. 
     Another aspect of the disclosure provides a computer-implemented method comprising, as implemented by a first light head having one or more processors and a first green light, receiving a light head control message; receiving a first status message from a second light head, where the first status message indicates that a second green light is off; receiving a second status message from the second light head, where the second status message indicates that a red light is on; in response to reception of the second status message, determining that the first green light can be activated based on the light head control message; causing electrical power to pass through to the first green light to activate the first green light; generating a third status message indicating that the first green light is on; and transmitting the third status message to the second light head. 
     The computer-implemented method of the preceding paragraph can include any sub-combination of the following features: where determining that the first green light can be activated based on the light head control message further comprises: receiving a fourth status message from a crosswalk button, where the crosswalk button, when activated, causes a crosswalk sign to signal that pedestrians can cross an intersection in a first direction, where the first light head faces a second direction that is perpendicular to the first direction, and where the fourth status message indicates that the crosswalk sign is disabled, and in response to reception of the second and fourth status messages, determining that the first green light can be activated based on the light head control message; where the light head control message comprises an indication that the first green light is deactivated a threshold period of time after being activated, and where the computer-implemented method further comprises: receiving a fourth status message from a crosswalk button, where the crosswalk button, when activated, causes a crosswalk sign to signal that pedestrians can cross an intersection in a first direction, where the first light head faces the first direction, and where the fourth status message indicates that the crosswalk sign is enabled, determining that the threshold period of time has expired, determining that no status message indicating that the crosswalk sign is disabled has been received from the crosswalk button after reception of the fourth status message, and determining not to deactivate the first green light; where the computer-implemented method further comprises: receiving a fifth status message from the crosswalk button, where the fifth status message indicates that the crosswalk sign is disabled, and causing the electrical power to no longer pass through to the first green light to deactivate the first green light; and where receiving a light head control message further comprises receiving the light head control message from one of a controller or a third light head. 
     Another aspect of the disclosure provides non-transitory, computer-readable storage media comprising computer-executable instructions, where the computer-executable instructions, when executed by a first light head comprising a processor and a first green light, cause the first light head to perform operations comprising: processing a first status message received from a second light head, where the first status message indicates that a second green light is off; processing a second status message received from the second light head, where the second status message indicates that a red light is on; in response to reception of the second status message, determining that the first green light can be activated; causing electrical power received by the first light head to pass through to the first green light to activate the first green light; generating a third status message indicating that the first green light is on; and transmitting the third status message to the second light head. 
     The non-transitory, computer-readable storage media of the preceding paragraph can include any sub-combination of the following features: where the first light head further performs operations comprising: processing a fourth status message received from a crosswalk button, where the crosswalk button, when activated, causes a crosswalk sign to signal that pedestrians can cross an intersection in a first direction, where the first light head faces a second direction that is perpendicular to the first direction, and where the fourth status message indicates that the crosswalk sign is disabled, and in response to reception of the second and fourth status messages, determining that the first green light can be activated; where the first light head is configured to deactivate the first green light a threshold period of time after activating the first light head, and where the first light head further performs operations comprising: processing a fourth status message received from a crosswalk button, where the crosswalk button, when activated, causes a crosswalk sign to signal that pedestrians can cross an intersection in a first direction, where the first light head faces the first direction, and where the fourth status message indicates that the crosswalk sign is enabled, determining that the threshold period of time has expired, determining that no status message indicating that the crosswalk sign is disabled has been received from the crosswalk button after reception of the fourth status message, and determining not to deactivate the first green light; where the first light head further performs operations comprising: processing a fifth status message received from the crosswalk button, where the fifth status message indicates that the crosswalk sign is disabled, and causing the electrical power to no longer pass through to the first green light to deactivate the first green light; and where the first light head receives the electrical power from a solar panel coupled to a pole to which the first light head is coupled. 
     Another aspect of the disclosure provides a system comprising: a traffic control box located at a street intersection, where the traffic control box comprises a controller; a first light head comprising a processor, a red light, a yellow light, and a green light; a pole extending upward from a street that forms a portion of the street intersection, the pole configured to support the first lead head above the street intersection, where the pole comprises a conduit that extends from the traffic control box to the first light head; and a single cable coupled to the controller and the processor, where the single cable passes through the conduit in the pole to couple to the controller and the processor, and where the single cable is configured to carry electrical power from the controller to the processor and to transmit data between the controller and the processor. 
     The system of the preceding paragraph can include any sub-combination of the following features: where the processor is configured to route the electrical power received via the single cable to one of the red light, the yellow light, or the green light to cause the respective light to illuminate; where the data comprises a light head control message, the light head control message comprising instructions used by the processor to determine when to enable or disable at least one of the red light, the yellow light, or the green light; where the traffic control box further comprises a power distribution module, where the power distribution module is configured to: convert alternating current (AC) electrical power into direct current (DC) power, and route the DC power to the controller; and where the single cable is a single Ethernet cable. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Throughout the drawings, reference numbers may be re-used to indicate correspondence between referenced elements. The drawings are provided to illustrate example embodiments described herein and are not intended to limit the scope of the disclosure. 
         FIG.  1 A  illustrates an exemplary block diagram depicting an improved vehicle traffic signal control system, which includes traffic control box and various light heads. 
         FIG.  1 B  illustrates an exemplary location of the traffic control box and the light heads of  FIG.  1 A  at an intersection. 
         FIG.  2    illustrates an exemplary block diagram depicting a non network-based vehicle traffic signal control system, which includes traffic control box and various light heads. 
         FIGS.  3 A- 3 B  are block diagrams of the operations performed by the components of the improved vehicle traffic signal control system to enable and/or disable light head lights. 
         FIG.  4 A  illustrates an exemplary block diagram depicting a version of the improved vehicle traffic signal control system of  FIG.  1 A  that includes various crosswalk buttons. 
         FIG.  4 B  illustrates an exemplary location of the crosswalk buttons of FIG. 
         FIGS.  5 A- 5 B  are additional block diagrams of the operations performed by the components of the improved vehicle traffic signal control system to enable and/or disable light head lights. 
         FIG.  6    illustrates an exemplary block diagram depicting a version of the improved vehicle traffic signal control system of  FIG.  1 A  that includes other components in addition to the various crosswalk buttons of  FIG.  4 A . 
         FIG.  7    is a flow diagram depicting a light control routine, according to one embodiment. 
         FIG.  8    is a flow diagram depicting a traffic signal retrofit routine, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     Introduction to an Improved Vehicle Traffic Signal Control System 
     As described above, a control box in a typical vehicle traffic signal control system may include a controller, a power distribution module, output relays, digital inputs, and a conflict monitor. The output relays may be used to control each light in a light head, each crosswalk indicator, and/or other auxiliary equipment (e.g., railroad crossing indicators, etc.). For example, one relay may be used to turn on a light in a light head. Thus, the control box can include N relays, where N represents the sum of the total number of lights in the light head(s) at the intersection, the total number of crosswalk indicators at the intersection, and/or the total number of auxiliary equipment outputs. When enabled, a relay may deliver 120VAC or other voltage to the connected light or crosswalk indicator, thereby turning on the light or crosswalk indicator. The controller in the typical control box may determine and control which relays are enabled and which are disabled. For example, the controller may be connected to each relay and send a low power signal to a relay that should be enabled. The controller can vary the duration of time that a relay is enabled based on whether a pedestrian presses a crosswalk button (e.g., relays controlling lights parallel to the direction in which a pedestrian would like to cross may remain enabled longer when a pedestrian presses a crosswalk button), the time of day, etc. The controller can also rapidly enable and disable relays, such as to cause the red lights to flash at an intersection, a crosswalk indicator to flash to indicate that the time to cross is ending, and/or the like. 
     The conflict monitor in the typical control box may monitor the low power signals sent by the controller to the relays and/or the outputs from the relays. If there is a conflict (e.g., an output is sent to the relay controlling a green light facing North at the same time that an output is sent to the relay controlling a green light facing West such that perpendicular green lights are both enabled), the conflict monitor can override the controller and cause all the red lights at the intersection to flash, disabling the intersection until the intersection is serviced in some embodiments. 
     In total, there may be a certain number of wires that connect each light head to the typical control box, where the number depends on the number of lights in the respective light head. As an illustrative example, if a light head includes three lights (e.g., red, yellow, and green), then there may be five wires that connect the light head to the typical control box: a 120VAC power line to the red light, a 120VAC power line to the yellow light, a 120VAC power line to the green light, neutral, and ground. In another illustrative example, the power lines to each light may be 48VDC. Because of the high voltage delivered to each light in a light head, the wires can have a wide diameter (e.g., a diameter greater than 2.06 mm). In this example, if the intersection includes three other light heads with three lights each, this means that there may be 20 bulky wires (e.g., 20 wires that each have wide diameters) extending from the typical control box to the various light heads (e.g., five bulky wires extending to each light head, where the diameter of a bundled set of the five bulky wires may be 10 mm, 20 mm, etc.). The number of bulky wires increases as the number of lights and/or light heads present at an intersection increases. 
     Furthermore, bulky wires may be routed from the typical control box to underground coils (e.g., for sensing vehicles), to crosswalk buttons (e.g., to detect when a pedestrian would like to cross an intersection), and/or to other sensors that may be present at the intersection. Thus, additional bulky wires extending from the typical control box may be present to accommodate other sensors that are used to control the flow of traffic. 
     The size of all these wires can increase construction costs by requiring larger underground and/or above-ground conduits to route the wires. In some cases, space near an intersection may be limited due to the presence of other structures or other conduits near an intersection (e.g., buildings, overpasses, bridges, tunnels, gas lines, water mains, etc.). Given the space constraints, the number of lights and/or light heads that can be added to an existing intersection or placed at a new intersection may be limited, and a planner may be forced to make design choices that prevent the use of newer technologies (e.g., cameras, light emitting diode (LED) lights, Internet-of-Things (IoT) devices, etc.) at the intersection that could improve traffic flow. Even if space near an intersection is not limited, the cost of adding new conduits to route wires for new lights or technologies can be prohibitive. For example, construction crews may have to tear up an existing intersection to add new conduits. Such actions can significantly increase construction costs and negatively impact traffic (e.g., cause congestion or other delays for motorists and/or pedestrians), possibly restricting the ability to quickly roll out new technology or otherwise upgrade existing intersections. 
     Accordingly, a low-cost, feature-rich improved vehicle traffic signal control system that uses Ethernet and/or wireless technologies is described herein. For example, like the typical vehicle traffic signal control system, the improved vehicle traffic signal control system may include a control box. However, the control box in the improved vehicle traffic signal control system may include fewer components and/or fewer wires extending therefrom as compared to the typical control box. In particular, the control box in the improved vehicle traffic signal control system may not include relays, a conflict monitor, or other similar components. Rather, the improved control box may simply include a controller that is coupled to various light heads via Ethernet cables. The Ethernet cables can carry electrical power, thereby providing power to the light heads. The light heads can include processors that use network technology to control light activation, to perform conflict monitoring, to receive data from various sensors to adjust traffic flow, and/or the like. Additional details of the improved vehicle traffic signal control system are described herein with respect to  FIGS.  1 A- 1 B and  3 A through  8   . 
       FIG.  1 A  illustrates an exemplary block diagram depicting an improved vehicle traffic signal control system, which includes traffic control box  100  and various light heads  140 N,  140 S,  140 W, and/or  140 E. The traffic control box  100  and the light heads  140 N,  140 S,  140 W, and/or  140 E may be associated with a single intersection. For example, the traffic control box  100  may be an enclosure located underneath an intersection, adjacent to an intersection (e.g., above ground, such as next to a sidewalk at the intersection, or below ground, such as below a sidewalk at the intersection or below undeveloped land or a structure within a certain distance of the intersection), or remote from the intersection (e.g., located a threshold distance from the intersection, such as 1 or 2 blocks from the intersection (e.g., when one controller is used to control offset intersections), etc.). The light heads  140 N,  140 S,  140 W, and/or  140 E may be located on poles, cables, or other structures that may optionally extend upward from the street (or from a location adjacent to the street, such as a sidewalk) and that can support the light heads  140 N,  140 S,  140 W, and/or  140 E above the intersection or the streets that form the intersection. 
     As an example,  FIG.  1 B  illustrates an exemplary location of the traffic control box  100  and the light heads  140 N,  140 S,  140 W, and/or  140 E at an intersection  180 . For example, the light head  140 N may be positioned above street  182  and face vehicles heading North, the light head  140 S may be positioned above the street  182  and face vehicles heading South, the light head  140 W may be positioned above street  184  and face vehicles heading West, and the light head  140 E may be positioned above the street  184  and face vehicles heading East. The traffic control box  100  may be located adjacent to streets  182  and  184  (e.g., above and/or below ground), near the Northeast corner of the intersection  180 . 
     While  FIGS.  1 A- 1 B  depict four light heads  140 N,  140 S,  140 W, and/or  140 E, this is for illustrative purposes only and is not meant to be limiting. For example, the improved vehicle traffic signal control system can include any number of light heads facing any number of directions. As an illustrative example, two light heads could be positioned above the street  182  and face vehicles heading North, where the first light head includes lights for vehicles that intend to continue North on the street  182  through the intersection, and where the second light head includes turn signal lights for vehicles that intend to turn West onto the street  184  from the street  182 . Similarly, two (or more) light heads could be positioned above the street  182  and face vehicles heading South, two (or more) light heads could be positioned above the street  184  and face vehicles heading West, and/or two (or more) light heads could be positioned above the street  184  and face vehicles heading East. 
     Furthermore, while  FIG.  1 B  depicts an intersection of two streets  182  and  184 , this is for illustrative purposes only and is not meant to be limiting. The features of the improved vehicle traffic signal control system disclosed herein can apply to any number of intersecting streets. 
     As illustrated in  FIG.  1 A , each light head  140 N,  140 S,  140 W,  140 E includes a processor  142 N,  142 S,  142 W, or  142 E, a red light  144 N,  144 S,  144 W, or  144 E, a yellow light  146 N,  146 S,  146 W, or  146 E, and a green light  148 N,  148 S,  148 W, or  148 E. The number of lights in each light head  140 N,  140 S,  140 W,  140 E is not meant to be limiting, however. In general, each light head  140 N,  140 S,  140 W,  140 E may include one or more processors  142 N,  142 S,  142 W, and/or  142 E. However, each light head  140 N,  140 S,  140 W,  140 E can include any number of lights and/or a different number of lights. For example, the light head  140 N could include two red lights (e.g., one red light for through traffic and one red light for left turn traffic) and two green lights (e.g., one green light for through traffic and one green light for left turn traffic), but the light head  140 W could include one red light (e.g., one red light for both through and left turn traffic) and two green lights (e.g., one green light for through traffic and one green light for left turn traffic). 
     The traffic control box  100  includes a controller  120  and a power distribution module  130 . The controller  120  may include one or more processors, memory, a network interface (e.g., network switch  125 ), and/or other hardware components. The one or more processors of the controller  120  can be configured to execute computer-executable instructions stored in the memory that, when executed, cause the controller  120  to perform the operations described herein. For example, the controller  120  can be configured to generate one or more light head control messages. A light head control message may include a set of rules or instructions that define how long a red light, yellow light, and/or green light should be enabled (e.g., activated, turned on, etc.), what conditions should be satisfied in order to enable a red light, a yellow light, and/or a green light, and/or what conditions should be satisfied in order to disable (e.g., deactivate, turn off, etc.) a red light, a yellow light, and/or a green light. Additional details of the light head control message are provided below. 
     The controller  120  can include a network switch  125  used to transmit the light head control message to one or more of the processors  142 N,  142 S,  142 W, and/or  142 E of the light head(s)  140 N,  140 S,  140 W, and/or  140 E. For example, each processor  142 N,  142 S,  142 W,  142 E may be coupled to the network switch  125  via the same cable (e.g., an Ethernet cable) or via one or more different cables (e.g., processors  142 N and  142 S can be coupled to the network switch  125  via a first Ethernet cable and processors  142 W and  142 E can be coupled to the network switch  125  via a second Ethernet cable, processors  142 N,  142 S,  142 W, and/or  142 E can each be coupled to the network switch  125  via a different Ethernet cable, etc.). For simplicity,  FIG.  1 A  depicts each processor  142 N,  142 S,  142 W, and/or  142 E being coupled to the network switch  125  via a different Ethernet cable. The Ethernet cable(s) can be designed with additional shielding and/or other features that enable the cable(s) to last for an extended period of time (e.g., 30 years, 40 years, 50 years, etc.). 
     Furthermore, the light heads  140 N,  140 S,  140 W, and/or  140 E can communicate with each other via the network switch  125 . For example, the light heads  140 N,  140 S,  140 W, and/or  140 E can communicate with each other to identify the status of other light heads  140 N,  140 S,  140 W, and/or  140 E, to determine when to enable or disable lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E (e.g., using the rules or instructions included in a received light head control message as a guide), and/or to perform conflict monitoring. Additional details of the communications between light heads  140 N,  140 S,  140 W, and/or  140 E are provided below. 
     Alternatively or in addition, not shown, the processors  142 N,  142 S,  142 W, and/or  142 E and/or the controller  120  can communicate with each other wirelessly. For example, the controller  120  can include a wireless router or transmitter that is configured to transmit light head control messages to one or more of the processors  142 N,  142 S,  142 W, and/or  142 E (or to a network interface included in the light heads  140 N,  140 S,  140 W, and/or  140 E) via a wireless network (e.g., BLUETOOTH, WIFI, a cellular network, etc.). Other components described herein (e.g., sensors, camera, IoT devices, crosswalk buttons, etc.) can also communicate with the controller  120  and/or light heads  140 N,  140 S,  140 W, and/or  140 E wirelessly. 
     In addition, the controller  120  may be configured to route electrical power to one or more of the light heads  140 N,  140 S,  140 W, and/or  140 E. For example, the power distribution module  130  may be coupled to a mains electricity system (e.g., a system that provides alternating-current (AC) electrical power). The power distribution module  130  can route the electrical power to the controller  120 . The electrical power may be 120V with a frequency of 60 Hz, 230V with a frequency of 50 Hz, 230V with a frequency of 60 Hz, and/or similar voltage and frequency combinations. In some embodiments, the power distribution module  130  converts the AC electrical power into direct current (DC) electrical power and routes the DC electrical power to the controller  120 . In other embodiments, the power distribution  130  routes the AC electrical power to the controller  120 . 
     The controller  120 , via the network switch  125 , can then route the electrical power to the various light heads  140 N,  140 S,  140 W, and/or  140 E via the Ethernet cable(s). In particular, the controller  120  can use Power over Ethernet (PoE) technology to pass both electrical power and data (e.g., light head control messages) over the wires that comprise an Ethernet cable. The Ethernet cable(s) can be coupled to the controller  120  on one end, and pass through one or more conduits present in poles or other structures that support one or more of the light heads  140 N,  140 S,  140 W, and/or  140 E to couple to one or more of the light heads  140 N,  140 S,  140 W, and/or  140 E on the other end (e.g., the conduit(s) may extend from the traffic control box  100  to one or more light heads  140 N,  140 S,  140 W, and/or  140 E). As an illustrative example, the controller  120  can transmit electrical power and data over the same wires that comprise an Ethernet cable. As another illustrative example, the controller  120  can transmit electrical power over a first set of wires that partially comprises an Ethernet cable and can transmit data over a second set of wires that partially comprises the same Ethernet cable. In some embodiments, a first set of wires (e.g., a first pair of wires) that partially comprises an Ethernet cable carry positive electrical power (e.g., DC+) and a second set of wires (e.g., a second pair of wires) that partially comprises an Ethernet cable carry negative electrical power (e.g., DC−). 
     The light heads  140 N,  140 S,  140 W, and/or  140 E can use the electrical power provided over the Ethernet cables to enable the red lights  144 N,  144 S,  144 W, and/or  144 E, the yellow lights  146 N,  146 S,  146 W, and/or  146 E, and/or the green lights  148 N,  148 S,  148 W, and/or  148 E. For example, the processor  142 N can determine whether the red light  144 N, the yellow light  146 N, or the green light  148 N should be enabled. Once the determination is made, the processor  142 N (or a power distribution component in the light head  140 N, not shown) can route the received electrical power to the light  144 N,  146 N, or  148 N that is to be enabled. As an illustrative example, the processor  142 N can cause a switch or relay to close, thereby closing a circuit loop, which causes current to pass through the light  144 N,  146 N, or  148 N that is to be enabled. The closed circuit loop can include the light  144 N,  146 N, or  148 N that is to be enabled, where closure of the switch or relay causes the light  144 N,  146 N, or  148 N to be coupled to both the first set of wires in the Ethernet cable that carry positive electrical power and the second set of wires in the Ethernet cable that carry negative electrical power. The current passing through the light  144 N,  146 N, and/or  148 N causes the light  144 N,  146 N, and/or  148 N to illuminate or produce light. The light  144 N,  146 N, and/or  148 N remains on until electrical power is no longer supplied to the light  144 N,  146 N, and/or  148 N (e.g., until the processor  142 N stops supplying electrical power to the light  144 N,  146 N, and/or  148 N by, for example, causing a switch or relay to open). 
     In some embodiments, the red lights  144 N,  144 S,  144 W, and/or  144 E, the yellow lights  146 N,  146 S,  146 W, and/or  146 E, and/or the green lights  148 N,  148 S,  148 W, and/or  148 E each include a light bulb (e.g., a 120V light bulb, a 130V light bulb, a 230V light bulb, etc.) and a colored covering housing the light bulb that produces the red, yellow, or green color. Such light bulbs may each consume a large amount of power (e.g., more than 100 W). Earlier versions of the PoE standard (e.g., IEEE 802.3af-2003 and IEEE 802.3at-2009) limited the amount of electrical power that could be supplied via the Ethernet cable to less than 25.5 W. If an earlier PoE standard is implemented and the light head  140 N,  140 S,  140 W, and/or  140 E to which electrical power is being supplied includes light bulbs, then multiple PoE Ethernet cables can be coupled between the controller  120  and the light head  140 N,  140 S,  140 W, and/or  140 E such that enough electrical power is provided to the light head  140 N,  140 S,  140 W, and/or  140 E to enable the lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E. However, current and/or future versions of the PoE standard (e.g., IEEE 802.3bt, IEEE 802.3bu, etc.) define increased power limits (e.g., 5 5W, 90 W-100 W, etc.). Thus, if a newer PoE standard is implemented and the light head  140 N,  140 S,  140 W, and/or  140 E to which electrical power is being supplied includes light bulbs, then one (or two) PoE Ethernet cable coupled between the controller  120  and the light head  140 N,  140 S,  140 W, and/or  140 E may be sufficient to allow the light head  140 N,  140 S,  140 W, and/or  140 E to enable the lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E. 
     In other embodiments, the red lights  144 N,  144 S,  144 W, and/or  144 E, the yellow lights  146 N,  146 S,  146 W, and/or  146 E, and/or the green lights  148 N,  148 S,  148 W, and/or  148 E each include one or more colored light emitting diodes (LEDs) arranged in a matrix pattern. The LEDs may consume less power than the traditional light bulbs (e.g., the 
     LEDs that form a single light  144 ,  146 , or  148  may collectively consume about 1 W, whereas a light bulb may consume more than 100 W) and may last longer than the traditional light bulbs. Given the low power usage, a single PoE Ethernet cable coupled between the controller  120  and a light head  140 N,  140 S,  140 W, and/or  140 E may be sufficient to allow the light head  140 N,  140 S,  140 W, and/or  140 E to enable the lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E, regardless of which PoE standard is implemented. In addition, because of the low power usage, the Ethernet cable may require less shielding, reducing the diameter of the Ethernet cable to less than the diameter of the current wires that carry electrical power to the light head lights (e.g., the Ethernet cable diameter may be 5 mm instead of 50 mm, 100 mm, 200 mm, etc.). Thus, adding light heads  140  with LEDs instead of light bulbs to intersections or retrofitting existing light heads  140  to include LEDs instead of light bulbs may result in fewer and less bulky cables or wires being needed to supply enough electrical power to the light heads  140 . As a result, an increased number of light heads  140  and/or other components (e.g., sensors, cameras, IoT devices, etc.) can placed at an intersection even with the presence of significant physical space constraints. 
     Unlike the improved vehicle traffic signal control system illustrated in  FIGS.  1 A- 1 B , a non network-based vehicle traffic signal control system includes additional components and additional bulky wires.  FIG.  2    illustrates an exemplary block diagram depicting a non network-based vehicle traffic signal control system, which includes traffic control box  200  and various light heads  240 N,  240 S,  240 W, and/or  240 E. For simplicity, the non network-based vehicle traffic signal control system depicted in  FIG.  2    represents the control system for an intersection that includes four lights that each include a single red, yellow, and green light. 
     As illustrated in  FIG.  2   , the traffic control box  200  includes a controller  220 , a power distribution module  230 , a conflict monitor  250 , various red relays  264 N,  264 S,  264 W, and/or  264 E, various yellow relays  266 N,  266 S,  266 W, and/or  266 E, and various green relays  268 N,  268 S,  268 W, and/or  268 E. The power distribution module  230  can be coupled to a mains electricity system and supply electrical power (e.g., 120VAC) to the red relays  264 N,  264 S,  264 W, and/or  264 E, the yellow relays  266 N,  266 S,  266 W, and/or  266 E, and the green relays  268 N,  268 S,  268 W, and/or  268 E. Each relay  264 N,  264 S,  264 W,  264 E,  266 N,  266 S,  266 W,  266 E,  268 N,  268 S,  268 W,  268 E is coupled to and provides electrical power to a particular light in a light head  240 N,  240 S,  240 W, and/or  240 E when the respective relay  264 N,  264 S,  264 W,  264 E,  266 N,  266 S,  266 W,  266 E,  268 N,  268 S,  268 W,  268 E is enabled. For example, each light head  240 N,  240 S,  240 W,  240 E includes a red light  244 N,  244 S,  244 W, and/or  244 E, a yellow light  246 N,  246 S,  246 W, and/or  246 E, and a green light  248 N,  248 S,  248 W, and/or  248 E. The red relay  264 N is coupled to and provides electrical power to the red light  244 N when enabled, the yellow relay  264 N is coupled to and provides electrical power to the yellow light  246 N when enabled, the green relay  266 N is coupled to and provides electrical power to the green light  248 N when enabled, the red relay  264 S is coupled to and provides electrical power to the red light  244 S when enabled, and so on. 
     The controller  220  determines which lights to enable and/or disable, and sends appropriate control signals to the relays  264 N,  264 S,  264 W,  264 E,  266 N,  266 S,  266 W,  266 E,  268 N,  268 S,  268 W, and/or  268 E to enable or disable the receiving relay. For example, if the controller  220  determines that yellow light  264 E of the light head  240 E should be enabled, the controller  220  can transmit a control signal to the yellow relay  266 E. Reception of the control signal may cause the yellow relay  266 E to close a switch that enables the electrical power received from the power distribution module  230  to be supplied to the yellow light  246 E or the yellow relay  266 E to otherwise cause the electrical power received from the power distribution module  230  to be supplied to the yellow light  246 E. Reception of the electrical power causes the yellow light  246 E to then illuminate. 
     The relays  264 N,  264 S,  264 W,  264 E,  266 N,  266 S,  266 W,  266 E,  268 N,  268 S,  268 W, and/or  268 E are further coupled with the respective light heads  240 N,  240 S,  240 W, and/or  240 E via a neutral wire and a ground wire. Thus, if a light head  240 N,  240 S,  240 W, and/or  240 E includes three lights, then five wires (e.g., three power wires for the three lights, a neutral wire, and a ground wire) may couple the light head  240 N,  240 S,  240 W, and/or  240 E to the traffic control box  200 . As mentioned above, these wires may be shielded to protect from interference. Thus, five bulky wires may couple the light head  240 N,  240 S,  240 W, and/or  240 E to the traffic control box  200 . With four light heads  240 N,  240 S,  240 W, and/or  240 E at an intersection, this results in  20  bulky wires coupling the light heads  240 N,  240 S,  240 W, and/or  240 E to the traffic control box  200 . 
     In the improved vehicle traffic signal control system described herein, however, these 20 bulky wires and the relays  264 N,  264 S,  264 W,  264 E,  266 N,  266 S,  266 W,  266 E,  268 N,  268 S,  268 W, and/or  268 E can be removed. Rather, the electrical power can be continuously supplied directly to the light heads  140 N,  140 S,  140 W, and/or  140 E by the controller  120  via one or more Ethernet cables using the PoE standard. The light heads  140 N,  140 S,  140 W, and/or  140 E themselves can then control which lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E receive the electrical power. Specifically, the processors  142 N,  142 S,  142 W, and/or  142 E can perform the light activation decision making instead of the controller  120 , supplying electrical power only to those lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E that the processors  142 N,  142 S,  142 W, and/or  142 E determine should be enabled. Thus, the processors  142 N,  142 S,  142 W, and/or  142 E (or a power distribution component in a light head  140 N,  140 S,  140 W, and/or  140 E) can control which lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E receive the electrical power. 
     To ensure that conflicts are prevented (e.g., situations in which two green lights in perpendicular directions and both directed to through traffic are both enabled simultaneously), the traffic control box  200  includes the conflict monitor  250 . The conflict monitor  250  can monitor the control signals transmitted by the controller  220 , identifying any situations in which the controller  220  has transmitted control signals to two or more different relays  264 N,  264 S,  264 W,  264 E,  266 N,  266 S,  266 W,  266 E,  268 N,  268 S,  268 W, and/or  268 E that should not be enabled at the same time (e.g., each of the green relays  268 N,  268 S,  268 W,  268 E). If the conflict monitor  250  identifies a situation in which control signals are transmitted to two or more different relays  264 N,  264 S,  264 W,  264 E,  266 N,  266 S,  266 W,  266 E,  268 N,  268 S,  268 W, and/or  268 E that should not be enabled at the same time, then conflict monitor  250  can override the controller  220 , transmitting one or more control signals to the relays  264 N,  264 S,  264 W,  264 E,  266 N,  266 S,  266 W,  266 E,  268 N,  268 S,  268 W, and/or  268 E to cause the red lights  244 N,  244 S,  244 W, and/or  244 E to flash. 
     In the improved vehicle traffic signal control system described herein, however, the conflict monitor  250  can be removed. Rather, the functionality provided by the conflict monitor  250  can be implemented by the processors  142 N,  142 S,  142 W, and/or  142 E in the light heads  140 N,  140 S,  140 W, and/or  140 E. For example, the light head control message, which is provided to each processor  142 N,  142 S,  142 W,  142 E, includes a set of rules or instructions that define, at least in part, what conditions should be satisfied in order to enable a red light, a yellow light, and/or a green light and/or what conditions should be satisfied in order to disable a red light, a yellow light, and/or a green light. The processors  142 N,  142 S,  142 W, and/or  142 E can communicate with each other, transmitting status messages that provide the current light status (e.g., information indicating which lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E are enabled and which are not). Thus, each processor  142 N,  142 S,  142 W,  142 E can use the status messages and the rules received as part of the light head control message to determine whether it is appropriate (e.g., in terms of avoiding conflicts) to enable or disable a red light  144 N,  144 S,  144 W, and/or  144 E, enable or disable a yellow light  146 N,  146 S,  146 W, and/or  146 E, and/or enable or disable a green light  148 N,  148 S,  148 W, and/or  148 E. As described herein, the processors  142 N,  142 S,  142 W, and/or  142 E can also receive status messages from other devices, such as cameras, sensors, IoT devices, etc., that may be considered by the processors  142 N,  142 S,  142 W, and/or  142 E when determining what actions are appropriate. 
     Light Head Communication 
     As described above, a light head control message includes a set of rules or instructions that define how long a red light, yellow light, and/or green light should be enabled, what conditions should be satisfied in order to enable a red light, a yellow light, and/or a green light, and/or what conditions should be satisfied in order to disable a red light, a yellow light, and/or a green light. As an illustrative example, a light head control message includes information indicating that green lights in the North-South direction (e.g., green lights  148 N and  148 S) are to remain enabled for 50 seconds, green lights in the East-West direction (e.g., green lights  148 W and  148 E) are to remain enabled for 30 seconds, and yellow lights in all directions are to remain enabled for 3 seconds (e.g., yellow lights  146 N,  146 S,  146 W, and/or  146 E). The light head control message further includes information indicating that green lights in the North-South direction cannot be enabled unless green and yellow lights in the East-West direction are disabled (e.g., green lights  148 W and  148 E and yellow lights  146 W and  146 E) and red lights in the East-West direction are enabled (e.g., red lights  144 W and  144 E). Similarly, the light head control message further includes information indicating that green lights in the East-West direction cannot be enabled unless green and yellow lights in the North-South direction (e.g., green lights  148 N and  148 S and yellow lights  146 N and  146 S) are disabled and red lights in the North-South direction are enabled (e.g., red lights  144 N and  144 S). Each light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E and/or each light head  140 N,  140 S,  140 W,  140 E may have a unique identifier, which can be included in the light head control message to specifically identify to which lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E and/or light heads  140 N,  140 S,  140 W, and/or  140 E the rules apply. 
     Each processor  142 N,  142 S,  142 W,  142 E can periodically transmit status messages to the other processors  142 N,  142 S,  142 W, and/or  142 E identifying the state of the associated lights via the network switch  125 . For example, a processor  142 N,  142 S,  142 W, and/or  142 E can transmit a status message when any associated light transitions from an on to off state or from an off to on state. The status message may include an identification of a light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E that has transitioned from one state to another (e.g., the unique identifier of the light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E) and the state to which the light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E transitioned. The processor  142 N,  142 S,  142 W, and/or  142 E can generate a separate status message for each independent light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E that changes state and/or the processor  142 N,  142 S,  142 W, and/or  142 E can generate a single status message for a plurality of lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E that change state (where the single status message includes information identifying each light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E that changed state and to what state the lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E changed). As an illustrative example, if the processor  142 S disables the previously enabled green light  148 S and enables the previously disabled yellow light  146 S, then the processor  142 S can either generate and transmit a single status message indicating that green light  148 S has transitioned to an off state and that yellow light  146 S has transitioned to an on state or generate and transmit two status messages, one for each light transition. 
     Because the processors  142 N,  142 S,  142 W, and/or  142 E each transmit status messages to the other processors  142 N,  142 S,  142 W, and/or  142 E, each processor  142 N,  142 S,  142 W,  142 E receives information that, in the aggregate, indicates the current status of all the lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E at the intersection. Thus, each processor  142 N,  142 S,  142 W,  142 E can use the status information and the light head control message rules to independently determine which lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E to enable and/or disable and when such transitions should take place. In this way, the improved vehicle traffic signal control system functions in a distributed manner, where each light head  140 N,  140 S,  140 W,  140 E makes its own light activation/deactivation decisions based on the state of other light heads  140 N,  140 S,  140 W, and/or  140 E. No light head  140 N,  140 S,  140 W, and/or  140 E necessarily must act as a master light head  140 N,  140 S,  140 W, and/or  140 E, instructing other slave light heads  140 N,  140 S,  140 W, and/or  140 E which lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E to enable and/or disable and when such transitions should take place. However, in other embodiments, one light head  140 N,  140 S,  140 W, or  140 E may act as a master light head  140 N,  140 S,  140 W, or  140 E and control the light activation/deactivation of other light heads  140 N,  140 S,  140 W, and/or  140 E. 
     The distributed processing of the improved vehicle traffic signal control system further allows the light heads  140 N,  140 S,  140 W, and/or  140 E to perform continuous or non-continuous self-diagnostic tests. For example, the light heads  140 N,  140 S,  140 W, and/or  140 E can perform checks to determine whether lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E are working properly, signals are being received from other light heads  140 N,  140 S,  140 W, and/or  140 E and/or the controller  120 , etc. Once a single instance of the self-diagnostic test is complete, the light heads  140 N,  140 S,  140 W, and/or  140 E can report to the controller  120  or a remote maintenance system the results of the self-diagnostic test. The controller  120  or remote maintenance system can then notify and/or dispatch technicians if a light head  140 N,  140 S,  140 W, and/or  140 E reports a problem. 
     In some embodiments, the controller  120  periodically transmits beacon signals to one or more of the processors  142 N,  142 S,  142 W, and/or  142 E to indicate that the controller  120  is still operating or functional. In addition, the controller  120  can include commands in the beacon signals that cause the processors  142 N,  142 S,  142 W, and/or  142 E to perform certain actions. For example, the controller  120  can include a termination command that causes the processors  142 N,  142 S,  142 W, and/or  142 E receiving the beacon signal to terminate an existing state. The controller  120  may include a termination command in a beacon signal if, for example, an emergency vehicle needs to cross an intersection. As an illustrative example, upon receiving a termination command in a beacon signal transmitted by the controller  120 , the processor  142 N can disable the green light  148 N (if enabled) or the yellow light  146 N (if enabled) even if it is not yet time for the green light  148 N or yellow light  146 N to transition from an on state to an off state. Optionally, if the processor  142 N receives the termination command while the red light  144 N is enabled, the processor  142 N may not transition the red light  144 N from an on state to an off state for a threshold period of time (e.g., as indicated in the termination command) even if it is time for the red light  144 N to transition from an on state to an off state. 
     In alternate embodiments, the controller  120  and/or the entire traffic control box  100  are not present. Rather, one light head  140 N,  140 S,  140 W, or  140 E can be designated as the “controller” and perform some or all of the functions described herein as being performed by the controller  120  (e.g., generate and transmit light head control messages to other light heads  140 N,  140 S,  140 W, and/or  140 E) in addition to performing the light head  140 N,  140 S,  140 W, and/or  140 E functions described herein. Because no traffic control box  100  may be present, the light heads  140 N,  140 S,  140 W, and/or  140 E can communicate wirelessly (e.g., each light head  140 N,  140 S,  140 W, and/or  140 E may include a wireless router). In addition, the light heads  140 N  140 S,  140 W, and/or  140 E can be coupled directly to an energy source. For example, solar panels, piezoelectric or other types of motion-based energy harvesting devices, and/or the like can be coupled to a light pole to which a light head  140 N,  140 S,  140 W, and/or  140 E is coupled to supply power to the light head  140 N,  140 S,  140 W, and/or  140 E. As another example, the light heads  140 N,  140 S,  140 W, and/or  140 E can be coupled to an above-ground or below-ground power source (e.g., a mains electricity system). Thus, the cost of the improved vehicle traffic signal control system can be reduced due to the absence of the controller  120  and/or traffic control box  100 . In addition, the reliability of the light heads  140 N,  140 S,  140 W, and/or  140 E may be increased because a hardware failure or other similar issue affecting a controller  120  or the traffic control box  100 , especially those issues that affect ground equipment more than aerial equipment (e.g., a vehicle hitting and damaging the traffic control box  100  and/or other equipment, flooding, etc.), is not a concern. As an illustrative example, this type of improved vehicle traffic signal control system can be set up on a rural road by a school that has a crosswalk. One of more light heads may communicate wirelessly and receive power from solar panels coupled to one or more light poles. Thus, no traffic control box  100  or other ground equipment may be present. The light heads may normally enable green lights to allow traffic on the rural road to pass the crosswalk. However, if a crosswalk button is selected, some or all the light heads may be notified accordingly, causing the light heads to disable the green lights and either enable the red lights or flash the yellow lights, thereby indicating that pedestrians are in the area and may be crossing. 
       FIGS.  3 A- 3 B  are block diagrams of the operations performed by the components of the improved vehicle traffic signal control system to enable and/or disable light head  140 N,  140 S,  140 W, and/or  140 E lights. As illustrated in  FIG.  3 A , the controller  120  generates a light head control message at ( 1 ). As an illustrative example, the light head control message includes data indicating that green lights  148 N and  148 S are to remain enabled for 50 seconds, green lights  148 W and  148 E are to remain enabled for 30 seconds, and yellow lights  146 N,  146 S,  146 W, and/or  146 E are to remain enabled for 3 seconds. The light head control message further includes data indicating that green lights  148 N and  148 S cannot be enabled unless green lights  148 W and  148 E and yellow lights  146 W and  146 E are disabled and red lights  144 W and  144 E are enabled, and that green lights  148 W and  148 E cannot be enabled unless green lights  148 N and  148 S and yellow lights  146 N and  146 S are disabled and red lights  144 N and  144 S are enabled. 
     The controller  120  then transmits the light head control message to the processors  142 N,  142 S,  142 W, and/or  142 E at ( 2 ). The controller  120  can periodically generate new light head control messages and transmit such messages to the processors  142 N,  142 S,  142 W, and/or  142 E. For example, traffic patterns may change based on the time of day, the day of the week, the week of the month, the month of the year, etc. In response, it may be desirable to adjust how long lights are enabled and/or disabled depending on the time, day, week, month, year, etc. The controller  120  can store a schedule of light enablement/disablement times, and generate and transmit a new light head control message when the schedule indicates that the light enablement/disablement times should change given the current time, day, week, month, year, etc. Alternatively, the initial light head control message can include a plurality of light enablement/disablement times, where each light enablement/disablement time is associated with a particular time, day, week, month, year, etc. The processors  142 N,  142 S,  142 W, and/or  142 E can then identify the current time and make light enablement and/or disablement determinations based at least in part on the current time. As another example, the controller  120  can generate and transmit a new light head control message if a new sensor or other component is added to an intersection that affects when lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E should be enabled and/or disabled. 
     In the example depicted in  FIG.  3 A , the processor  142 N has determined that the rules included in the received light head control message indicate that green light  148 N can be turned on (e.g., green lights  148 W and  148 E are off, yellow lights  146 W and  146 E are off, and red lights  144 W and  144 E are on). Thus, the processor  142 N supplies electrical power received via the Ethernet cable to the green light  148 N, thereby turning the green light  148 N on at ( 3 ). In some embodiments, not shown, the processor  142 S makes the same determination (e.g., because light heads  140 N and  140 S face opposite directions) and turns on the green light  148 S. In response to determining to turn on the green light  148 N, the processor  142 N generates and transmits a status message indicating that the green light  148 N is on at ( 4 ) to the processors  142 S,  142 W, and/or  142 E. 
     After a threshold period of time defined in the light head control message (e.g., 50 seconds), the processor  142 N determines that the green light  148 N should be disabled. Thus, after the threshold period of time, the processor  142 N turns the green light  148 N off at ( 5 ) (e.g., by stopping the supply of electrical power to the green light  148 N). In response, the processor  142 N generates and transmits a status message indicating that the green light  148 N is off at ( 6 ) to the processors  142 S,  142 W, and/or  142 E. 
     Once the green light  148 N is off, the processor  142 N can turn on the yellow light  146 N for a threshold period of time defined in the light head control message (e.g., 3 seconds), and then turn on the red light  144 N at ( 7 ) after the yellow light  146 N is turned off. The processor  142 N can then generate and transmit a status message indicating that the red light  144 N is on at ( 8 ) to the processors  142 S,  142 W, and/or  142 E. 
     In other embodiments, not shown, the processor  142 N combines one or more of the generated status messages. For example, the processor  142 N can combine the status message indicating that the green light  148 N is off and the status message indicating that the yellow light  146 N is on, transmitting a single status message to indicate the two light transitions. 
     At this stage, the processors  142 S,  142 W, and/or  142 E have received information indicating that green light  148 N is off, yellow light  146 N is off, and red light  144 N is on. Processors  142 N,  142 W, and  142 E may have also received information indicating that green light  148 S is off, yellow light  146 S is off, and red light  144 S is on (e.g., from the processor  142 S). Per the light head control message rules, the processors  142 W and  142 E can now enable green lights  148 W and  148 E, respectively. Thus, the processors  142 W and  142 E can disable the red lights  144 W and  144 E, respectively, and transmit corresponding status messages to the other processors  142 N,  142 S,  142 W, and/or  142 E. The processor  142 W can then turn on green light  148 W at ( 9 A) and the processor  142 E can turn on green light  148 E at ( 9 B), as illustrated in  FIG.  3 B . 
     Optionally, the processors  142 W and  142 E may turn on the respective green lights  148 W and  148 E a threshold time period (e.g., 1 second, 2 seconds) after receiving the status message indicating that the red light  144 N is on. Thus, the red lights  144 N,  144 S,  144 W, and/or  144 E may each be on at the same time, which may ensure that two drivers traveling in perpendicular directions could not both argue that they had a green light and the other driver had a red light if an accident were to occur, or which may allow a driver who meets the requirements of being in the intersection prior to the light turning red to exit the intersection prior to traffic in a perpendicular direction entering the intersection. 
     Alternatively, the processors  142 W and  142 E may turn on the respective green lights  148 W and  148 E after receiving the status message indicating that the red light  144 N is on and after a determination is made that no vehicles and/or pedestrians are present in the intersection  180 . For example, as discussed below, other components, such as sensors, cameras, and/or IoT devices, can be coupled to a light head. One or more sensors (e.g., a light detection and ranging (LIDAR) sensor, a radio detection and ranging (RADAR) sensor, an infrared sensor, a motion detector, a presence detector, etc.) and/or a camera can be coupled to the light head  140 N and output signals to the processor  142 N. Similarly, one or more sensors (e.g., a LIDAR sensor, a RADAR sensor, an infrared sensor, a motion detector, a presence detector, etc.) and/or a camera can be coupled to the light head  140 S output signals to the processor  142 S. The light head  140 N sensor(s) and/or camera may face South and can be used individually or in conjunction to identify objects (e.g., vehicles, pedestrians, bicyclists, etc.) that may be present in the southern half of the intersection  180 , in the northern half of the intersection  180 , in the northeastern quadrant of the intersection  180 , in the southeastern quadrant of the intersection  180 , in the northwestern quadrant of the intersection  180 , in the southwestern quadrant of the intersection  180 , and/or any combination thereof. The light head  140 S sensor(s) and/or camera may face North and can be used individually or in conjunction to identify objects (e.g., vehicles, pedestrians, etc.) that may be present in a portion of the intersection  180  not monitored by the light head  140 N sensor and/or camera (e.g., if the light head  140 N sensor(s) and/or camera identifies objects in the southern half of the intersection  180 , then the light head  140 S sensor(s) and/or camera identifies objects in the northern half of the intersection  180 , if the light head  140 N sensor(s) and/or camera identifies objects in the southeastern quadrant of the intersection  180 , then the light head  140 S sensor(s) and/or camera may identify objects in the northwestern quadrant of the intersection  180 , etc.). Similarly, light head  140 W sensor(s) and/or camera and/or light head  140 E sensor(s) and/or camera can monitor portions of the intersection  180  not monitored by the light head  140 N sensor(s) and/or camera and/or the light head  140 S sensor(s) and/or camera. Alternatively or in addition, some or all of the light head  140 N,  140 S,  140 W, and/or  140 E sensor(s) and/or camera(s) can monitor the same portions of the intersection  180 . In an embodiment, the intersection  180  includes crosswalks for monitoring purposes. If a sensor and/or camera detects an object in a monitored portion of the intersection  180 , the sensor and/or camera can transmit a signal indicating that an object is detected in the monitored portion. The processor  142 N,  142 S,  142 W, and/or  142 E that receives such a signal can transmit an object detection message to the other processors  142 N,  142 S,  142 W, and/or  142 E indicating that an object is detected in a portion of the intersection  180 . In response to receiving such a message (and/or in response to generating an object detection message themselves), the processors  142 W and  142 E may not turn on the respective green lights  148 W and  148 E even after receiving the status message indicating that the red light  144 N is on. Rather, the processors  142 W and  142 E may wait until one or more object detection messages are received (and/or generated by themselves) indicating that no object is detected in any portion of the intersection  180  before turning on the respective green lights  148 W and  148 E. As an illustrative example, if each light head sensor(s) and/or camera monitors a single quadrant of the intersection  180 , then the processor  142 W may turn on the green light  148 W after receiving a signal from the light head  140 W sensor(s) and/or camera indicating that no object is detected in the northeastern quadrant of the intersection  180 , after receiving an object detection message from the processor  142 N indicating that no object is detected in the southeastern quadrant of the intersection  180 , after receiving an object detection message from the processor  142 E indicating that no object is detected in the southwestern quadrant of the intersection  180 , and after receiving an object detection message from the processor  142 W indicating that no object is detected in the northwestern quadrant of the intersection  180 . However, the processor  142 W may not turn on the green light  148 W after receiving a signal from the light head  140 W sensor(s) and/or camera indicating that no object is detected in the northeastern quadrant of the intersection  180 , after receiving an object detection message from the processor  142 N indicating that no object is detected in the southeastern quadrant of the intersection  180 , after receiving an object detection message from the processor  142 E indicating that an object is detected in the southwestern quadrant of the intersection  180 , and after receiving an object detection message from the processor  142 W indicating that no object is detected in the northwestern quadrant of the intersection  180 . The processor  142 W may wait for another object detection message from the processor  142 E indicating that no object is detected in the southwestern quadrant of the intersection  180  before turning on the green light  148 W. Some or all of the processors  142 N,  142 S,  142 W, and/or  142 E may generate and transmit an object detection message after receiving a status message indicating that a red light  144 N,  144 S,  144 W, and/or  144 E is on. In addition, if a processor  142 N,  142 S,  142 W, and/or  142 E generates and transmits an object detection message indicating that an object is detected, the processor  142 N,  142 S,  142 W, and/or  142 E may generate another object detection message indicating that no object is detected when an object is no longer detected. Thus, processors  142 N,  1425 ,  142 W, and/or  142 E may wait for status message indicating that red lights  144 N,  144 S,  144 W, and/or  144 E are on and object detection messages that collectively indicate that no objects are detected in the intersection  180  before turning on any green lights  148 N,  148 S,  148 W, and/or  148 E. In this way, the light heads  140 N,  140 S,  140 W, and/or  140 E and corresponding sensor(s) and/or camera(s) can reduce the likelihood of accidents (e.g., T-bone collisions or other cross-traffic accidents) by preventing traffic from seeing green lights until the intersection is clear of cross-traffic. 
     In response to the green lights  148 W and  148 E being turned on, the processor  142 W generates and transmits a status message to processors  142 N,  142 S, and  142 E indicating that the green light  148 W is on at ( 10 A), and the processor  142 E generates and transmits a status message to processors  142 N,  142 S, and  142 W indicating that the green light  148 E is on at ( 10 B). By receiving the status messages, the processors  142 N and  142 S determine that the light head control message rules indicate that green lights  148 N and  148 S cannot be enabled, at least not until green lights  148 W and  148 E are disabled (e.g., after  30  seconds as defined in the light head control message). In this way, the processors  142 N,  142 S,  142 W, and/or  142 E perform their own conflict monitoring, thereby eliminating the need to include a separate, physical conflict monitoring device in the traffic signal box  100 . 
     Alternatively, not shown, the controller  120  may not transmit one or more light head control messages, allowing the processors  142 N,  142 S,  142 W, and/or  142 E to control light transitions thereafter. Rather, the controller  120  can periodically (e.g., every second) transmit a light head control message to each processor  142 N,  142 S,  142 W, and/or  142 E indicating in which state each respective light should be. For example, the light head control message can indicate whether lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E should be on or off. The status (e.g., whether a light should be on or off) for each of the lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E can be included in the same light head control message, the status for each light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E corresponding to a particular light head  140 N,  140 S,  140 W, and/or  140 E can be included in a light head control message associated with and transmitted to the particular light head  140 N,  140 S,  140 W, and/or  140 E, the status for a single light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, or  148 E or a group of lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E can be included in a single light head control message, and/or any combination thereof. Each processor  142 N,  142 S,  142 W, and/or  142 E can then enable or disable the respective lights according to the information provided in the received light head control message. 
     By periodically transmitting light head control messages to the processors  142 N,  142 S,  142 W, and/or  142 E indicating in which state each respective light should be, the controller  120  can ensure that clock errors do not lead to potential accidents. For example, the processors  142 N,  142 S,  142 W, and/or  142 E may use internal clocks to determine when lights should transition from one state to another. If there is an error in any one of the clocks of the processors  142 N,  142 S,  142 W, and/or  142 E, lights may transition at the wrong time, leading to situations like green light  148 N turning on before red light  144 E turns on. The controller  120  then can use light head control messages to avoid issues that arise from clock errors. 
     Additional Components in the Improved Vehicle Traffic Signal Control System 
       FIG.  1 A  illustrates a basic example of the improved vehicle traffic signal control system in which an intersection includes four light heads  140 N,  140 S,  140 W, and/or  140 E. However, by implementing the PoE standard and network technology, the improved vehicle traffic signal control system is flexible and can support the inclusion of sensors, cameras, IoT devices, and/or other components. For example, intersections often include crosswalk buttons and signs, where a crosswalk button, when activated, causes a crosswalk sign to signal to a pedestrian that it is safe to cross the street. One or more crosswalk buttons can be configured to communicate with the light heads  140 N,  140 S,  140 W, and/or  140 E via the network switch  125 . 
       FIG.  4 A  illustrates an exemplary block diagram depicting a version of the improved vehicle traffic signal control system of  FIG.  1 A  that includes various crosswalk buttons  440 . For example, the crosswalk buttons  440  may be located on poles or other structures present near the intersection, such as on poles that support the light heads  140 N,  140 S,  140 W, and/or  140 E. 
     As an example,  FIG.  4 B  illustrates an exemplary location of the crosswalk buttons  440 . For example, ( 1 ) crosswalk button  440 N- 1  can be located on the pole that supports the light head  140 N and, when selected, allow pedestrians to cross from the East side of the street  182  to the West side of the street  182 ; ( 2 ) crosswalk button  440 N- 2  can be located on a pole near the Northeast corner of the intersection  180  and, when selected, allow pedestrians to cross from the North side of the street  184  to the South side of the street  184 ; ( 3 ) crosswalk button  440 S- 1  can be located on the pole that supports the light head  140 S and, when selected, allow pedestrians to cross from the West side of the street  182  to the East side of the street  182 ; ( 4 ) crosswalk button  440 S- 2  can be located on a pole near the Southwest corner of the intersection  180  and, when selected, allow pedestrians to cross from the South side of the street  184  to the North side of the street  184 ; ( 5 ) crosswalk button  440 W- 1  can be located on the pole that supports the light head  140 W and, when selected, allow pedestrians to cross from the North side of the street  184  to the South side of the street  184 ; ( 6 ) crosswalk button  440 W- 2  can be located on a pole near the Northwest corner of the intersection  180  and, when selected, allow pedestrians to cross from the West side of the street  182  to the East side of the street  182 ; ( 7 ) crosswalk button  440 E- 1  can be located on the pole that supports the light head  140 E and, when selected, allow pedestrians to cross from the South side of the street  184  to the North side of the street  184 ; and ( 8 ) crosswalk button  440 E- 2  can be located on a pole near the Southeast corner of the intersection  180  and, when selected, allow pedestrians to cross from the East side of the street  182  to the West side of the street  182 . 
     When a crosswalk button  440  is enabled and causes an associated crosswalk sign to transition from signaling that pedestrians may not cross (e.g., represented as a red hand) to signaling that pedestrians may cross (e.g., represented as a white pedestrian symbol) and/or when the crosswalk sign transitions from signaling pedestrians may cross to signaling that pedestrians may not cross, the crosswalk button  440  can generate and transmit a status message to the light heads  140 N,  140 S,  140 W, and/or  140 E. The status message may include information indicating which crosswalk button  440  is transmitting the status message (e.g., each crosswalk button  440  may be associated with a unique identifier that can be included in the status message) and whether the crosswalk button  440  is enabled and allowing pedestrians to cross (e.g., the crosswalk sign signals pedestrians may cross) or whether the crosswalk button  440  is disabled and not allowing pedestrians to cross (e.g., the crosswalk sign signals pedestrians may not cross). 
     In addition to including information identifying what state other lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E must be in for a processor  142 N,  142 S,  142 W, and/or  142 E to enable or disable a light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E, the light head control message previously transmitted by the controller  120  to the light heads  140 N,  140 S,  140 W, and/or  140 E may include one or more rules or instructions defining what states the crosswalk buttons  440  must be in for the processor  142 N,  142 S,  142 W, and/or  142 E to enable or disable a light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E. As an illustrative example, a light head control message includes information indicating that green lights in the North-South direction (e.g., green lights  148 N and  148 S) cannot be enabled unless crosswalk buttons that allow pedestrians to cross in the East-West direction (e.g., crosswalk buttons  440 N- 1 ,  440 S- 1 ,  440 W- 2 , and  440 E- 2 ) are disabled, and green lights in the East-West direction (e.g., green lights  148 W and  148 E) cannot be enabled unless crosswalk buttons that allow pedestrians to cross in the North-South direction (e.g., crosswalk buttons  440 N- 2 ,  440 S- 2 ,  440 W- 1 , and  440 E- 1 ) are disabled. 
     In some embodiments, the rules in the light head control message can conflict. For example, the light head control message may indicate that green lights in the East-West direction (e.g., green lights  148 W and  148 E) and red lights in the North-South direction (e.g., red lights  144 N and  144 S) are to remain enabled for 30 seconds, but crosswalk buttons that allow pedestrians to cross in the East-West direction (e.g., crosswalk buttons  440 N- 1 ,  440 S- 1 ,  440 W- 2 , and  440 E- 2 ) may cause crosswalk signs to signal that pedestrians may cross for 40 seconds. Because the rules may further indicate that green lights in the North-South direction (e.g., green lights  148 N and  148 S) cannot be enabled while the crosswalk buttons that allow pedestrians to cross in the East-West direction are enabled, the green lights in the East-West direction and the red lights in the North-South direction may remain enabled for longer than 30 seconds in situations in which the East-West crosswalk buttons are enabled. Accordingly, the light head control message may indicate a priority or hierarchy of rules such that the processors  142 N,  142 S,  142 W, and/or  142 E may not inadvertently perform conflicting actions (e.g., allowing green lights in the North-South direction to turn on while the East-West crosswalk buttons are still enabled). In the example described above, the priority of rules may be as follows:
         1. Green lights in the North-South direction (e.g., green lights  148 N and  148 S) cannot be enabled unless green and yellow lights in the East-West direction (e.g., green lights  148 W and  148 E and yellow lights  146 W and  146 E) are off, red lights in the East-West direction (e.g., red lights  144 W and  144 E) are on, and crosswalk buttons in the East-West direction (e.g., crosswalk buttons  440 N- 1 ,  440 S- 1 ,  440 W- 2 , and  440 E- 2 ) are disabled   2. Crosswalk buttons in the East-West direction (e.g., crosswalk buttons  440 N- 1 ,  440 S- 1 ,  440 W- 2 , and  440 E- 2 ) are enabled for 40 seconds   3. Green lights in the East-West direction (e.g., green lights  148 W and  148 E) and red lights in the North-South direction (e.g., red lights  144 N and  144 S) remain enabled while the crosswalk buttons in the East-West direction (e.g., crosswalk buttons  440 N- 1 ,  440 S- 1 ,  440 W- 2 , and  440 E- 2 ) are enabled   4. Red lights in the North-South direction (e.g., red lights  144 N and  144 S) are enabled for 30 seconds   5. Green lights in the East-West direction (e.g., green lights  148 W and  148 E) are enabled for 30 seconds       

       FIGS.  5 A- 5 B  are additional block diagrams of the operations performed by the components of the improved vehicle traffic signal control system to enable and/or disable light head  140 N,  140 S,  140 W, and/or  140 E lights. As illustrated in  FIG.  5 A , the crosswalk button  440 N- 2  receives an indication that the crosswalk button  440 N- 2  has been activated at ( 1 ). In response, the crosswalk button  440 N- 2  can instruct the associated crosswalk sign to turn on a crosswalk message signaling that pedestrians may cross at ( 2 ). In some embodiments, the crosswalk buttons  440  can receive light head control messages and/or status messages in addition to the light heads  140 N,  140 S,  140 W, and/or  140 E. The crosswalk button  440 N- 2  may then instruct the associated crosswalk sign to turn on the crosswalk message after receiving status messages indicating that green lights  148 W and  148 E are off, yellow lights  146 W and  146 E are off, and red lights  144 W and  144 E are on (e.g., the light head control message may include a rule indicating that this condition must be satisfied in order for the associated crosswalk sign to be allowed to turn on the crosswalk message). 
     After causing the crosswalk message to turn on, the crosswalk button  440 N- 2  can generate and transmit a status message to the processors  142 N,  142 S,  142 W, and/or  142 E indicating that the crosswalk is on at ( 3 ). Thus, the processors  142 N,  142 S,  142 W, and/or  142 E can receive information indicating that a North-South crosswalk is enabled, thereby preventing the processors  142 W and  142 E from enabling the East-West green lights  148 W and  148 E, respectively. 
     Because the North-South crosswalk being enabled does not prevent a North-South green light  148 N and  148 S from being enabled, the processor  142 N may turn the green light  148 N on at ( 4 ). In response, the processor  142 N generates and transmits a status message to the processors  142 S,  142 W, and/or  142 E indicating that the green light  148 N is on at ( 5 ). Similarly, the processor  142 S may turn the green light  148 S on transmit a corresponding status message. 
     The processor  142 N may then determine that a threshold period of time has expired at ( 6 ). For example, the threshold period of time may be the period of time that the green light  148 N is to remain on as defined by the light head control message (e.g., 30 seconds). However, the processor  142 N has not yet received a status message from the crosswalk button  440 N- 2  indicating that the crosswalk message signaling that pedestrians may cross has been turned off. Thus, the processor  142 N determines at ( 7 ) not to turn the green light  148 N off and the red light  144 N on even though the threshold period of time has expired because the crosswalk message is still on. 
     At a later time, such as after a crosswalk threshold period of time (e.g., as defined by the light head control message, such as 40 seconds) has expired, the crosswalk button  440 N- 2  causes the crosswalk sign to turn off the crosswalk message signaling that pedestrians may cross at ( 8 ), as illustrated in  FIG.  5 B . In response, the crosswalk button  440 N- 2  generates and transmits to the processors  142 N,  142 S,  142 W, and/or  142 E a status message indicating that the crosswalk is off at ( 9 ). 
     Because the threshold period of time for keeping the green light  148 N enabled has already expired, the processor  142 N may turn the green light  148 N off at ( 10 ) after receiving the status message from the crosswalk button  440 N- 2 . In response, the processor  142 N generates and transmits to the processors  142 S,  142 W, and/or  142 E a status message indicating that the green light  148 N is off at ( 11 ). The processor  142 N can then enable the yellow light  146 N for a defined period of time (e.g., 3 seconds), transmitting a corresponding status message indicating that the yellow light  146 N is on and transmitting a corresponding status message indicating that the yellow light  146 N is off after the defined period of time. The processor  142 N can then turn the red light  144 N on at ( 12 ) and generate and transmit a status message to the processors  142 S,  142 W, and/or  142 E indicating that the red light  144 N is on at ( 13 ). 
     In some embodiments, not shown, the status messages transmitted by the  142 N,  142 S,  142 W, and/or  142 E and/or other crosswalk buttons  440  are also transmitted to the crosswalk button  440 N- 2 . The crosswalk button  440 N- 2  can use the status messages to determine when to cause the associated crosswalk sign to turn on the crosswalk message signaling that pedestrians may cross. 
       FIGS.  3 A- 3 B and  5 A- 5 B  are not meant to be limiting as other sequences of operations, not shown, can be performed by the controller  120  and/or the processors  142 N,  142 S,  142 W, and/or  142 E to enable and/or disable lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E and/or crosswalk buttons  440 N- 1 ,  440 N- 2 ,  440 S- 1 ,  440 S- 2 ,  440 W- 1 ,  440 W- 2 ,  440 E- 1 , and/or  440 E- 2 . In general, typical vehicle traffic signal control systems include a centralized processing unit that then activates outputs and receives data from sensors, using the received data to make decisions. However, the improved vehicle traffic signal control system can use multiple processing units located throughout the intersection (e.g., in the different light heads  140 N,  140 S,  140 W, and  140 E) to make decisions. 
     In some embodiments, other components in addition to the crosswalk buttons  440  can be included in the improved vehicle traffic signal control system and/or affect the light activation/deactivation determinations made by the processors  142 N,  142 S,  142 W, and/or  142 E.  FIG.  6    illustrates an exemplary block diagram depicting a version of the improved vehicle traffic signal control system of FIG. lA that includes other components in addition to the various crosswalk buttons  440 . For example, as illustrated in  FIG.  6   , the improved vehicle traffic signal control system includes one or more of a camera  650 , a temperature sensor  660 , a transponder  670 , a router  680 , or a vehicle sensor  690 . While  FIG.  6    depicts a single camera  650 , temperature sensor  660 , transponder  670 , router  680 , and vehicle sensor  690 , this is not meant to be limiting. Rather,  FIG.  6    depicts example components that optionally may be present at or near an intersection. Any number of these components can be present at or near an intersection. In addition, any number of other similar components, like IoT devices, can also be present at or near the intersection, be powered via the electrical power carried over the Ethernet cables, and/or interact with the traffic control box  100  and/or light heads  140  in a similar manner as described herein. 
     The camera  650  can be located on a pole supporting a light head and face traffic in the intersection to capture images and/or video. For example, the camera  650  can be located on a pole supporting the light head  140 N and face traffic traveling North. The camera  650  can be coupled to the network switch  125  via an Ethernet cable, and thus can be powered using the electrical power carried over the Ethernet cable. 
     The camera  650  may simply capture images and/or video for transmission via the traffic control box  100  and a network to a remote system (e.g., a traffic monitoring system). The images and/or video captured by the camera  650  can also be used by the light heads  140 N,  140 S,  140 W, and/or  140 E in making the light activation/deactivation determinations. For example, the camera  650  can transmit captured images and/or video to one or more of the processors  142 N,  142 S,  142 W, and/or  142 E. A processor  142 N,  142 S,  142 W, and/or  142 E can process the images and/or frames of the video to, for example, determine whether a vehicle is waiting at the intersection or is about to approach the intersection. As an illustrative example, if the camera  650  is located on the pole supporting the light head  140 N and faces traffic traveling North, the red light  144 N is on, and the green and yellow lights  148 N and  146 N are off, the processors  142 W and/or  142 E (e.g., the processors of the East-West light heads) can process the images and/or the frames of the video to identify whether there are any vehicles traveling North present at the intersection or approaching the intersection. If there are one or more vehicles traveling North present at the intersection or approaching the intersection, the time that the green lights  148 W and  148 E should be enabled has expired, and/or there are no vehicles traveling East or West present at the intersection or approaching the intersection (e.g., as determined based on processing images and/or video frames captured by another camera facing East and/or West, based on vehicle sensors present at the intersection, etc.), then the processors  142 W and/or  142 E can turn off the corresponding green lights  148 W and  148 E, respectively, and turn on the corresponding red lights  144 W and  144 E, respectively. This would then allow the processor  142 N to turn the green light  148 N on and allow the vehicle(s) traveling North to pass through the intersection. On the other hand, if there are no vehicles traveling North present at the intersection or approaching the intersection and the time that the green lights  148 W and  148 E should be enabled has expired, the processors  142 W and  142 E can keep the green lights  148 W and  148  E on even though the green light on time has expired given that there are no vehicles traveling North waiting to pass through the intersection. Thus, the improved vehicle traffic signal control system can more efficiently control the flow of traffic. 
     The temperature sensor  660  can be located on a pole supporting a light head or on another structure near an intersection. The temperature sensor  660  can be coupled to the network switch  125  via an Ethernet cable, and thus can be powered using the electrical power carried over the Ethernet cable. The temperature sensor  660  can measure temperatures at the intersection, transmitting the measured temperatures to the traffic control box  100  via the Ethernet cable (or via a wireless connection). The traffic control box  100  can then forward the measurements to a remote system via a network such that the measurements can be available, for example, on a content page (e.g., a network page, a web page, etc.). Alternatively or in addition, the temperature sensor  660  can measure temperatures at the intersection, transmitting the measured temperatures to the various processors  142 N,  142 S,  142 W, and/or  142 E via the Ethernet cable (or via a wireless connection). The processors  142 N,  142 S,  142 W, and/or  142 E can use the measured temperatures to, for example, modify when and for how long lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E are enabled and/or disabled. As an illustrative example, if the temperature drops below a certain value (e.g., 32° F.), vehicles may have a harder time stopping due to ice, snow, and/or the like. Thus, when the temperature drops below this value and a processor  142 N,  142 S,  142 W, and/or  142 E receives a status message indicating that a red light  144 N,  144 S,  144 W, and/or  144 E in a first direction (e.g., North) is now enabled, the processor  142 N,  142 S,  142 W, and/or  142 E may wait a longer than normal period of time (e.g., 5 seconds instead of 1 second) before enabling a green light  148 N,  148 S,  148 W, and/or  148 E in a second direction (e.g., West) to prevent possible accidents resulting from the low temperature. The same techniques can be applied to other sensors that measure weather conditions and that may be present at the intersection and communicate and receive electrical power via an Ethernet cable, such as humidity sensors, wind sensors, rain sensors, etc. 
     The transponder  670  can be located on a pole supporting a light head or on another structure near an intersection. The transponder  670  can be coupled to the network switch  125  via an Ethernet cable, and thus can be powered using the electrical power carried over the Ethernet cable. The transponder  670  can be used to override one or more light heads  140 N,  140 S,  140 W, and/or  140 E, causing one or more light heads  140 N,  140 S,  140 W, and/or  140 E to enable and/or disable specific lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E. For example, the transponder  670  can be used by law enforcement during emergencies to immediately turn green lights on in the direction being traveled by law enforcement and to turn red lights off in the direction(s) not being traveled by law enforcement. 
     The router  680  can be located on a pole supporting a light head or on another structure near an intersection. The router  680  can be coupled to the network switch  125  via an Ethernet cable, and thus can be powered using the electrical power carried over the Ethernet cable. The router  680  can be used to transmit communications to other intersections, such as information indicating the volume of vehicles that have traveled through the present intersection and that are expected to arrive at a next intersection and/or when the vehicles are expected to arrive at the next intersection. The router  680  can receive the relevant information from the light heads  140 N,  140 S,  140 W, and/or  140 E, the controller  120 , vehicle sensors (e.g., vehicle sensor  690 ), etc. 
     The vehicle sensor  690  can be located at an intersection or a certain distance from an intersection (e.g.,  50  feet from the intersection,  100  feet from the intersection,  200  feet from the intersection, etc.). For example, the vehicle sensor  690  can be an inductive coil located in and/or below the street asphalt at the intersection (e.g., adjacent to a crosswalk) or a certain distance from the intersection. If multiple vehicle sensors  690  are present, the vehicle sensors  690  can be located in different lanes of the street at the intersection, spaced apart between the intersection and a certain distance from the intersection (e.g., a vehicle sensor  690  can be placed at the intersection and every 50 feet away from the intersection for a total distance of 400 feet), and/or the like. 
     The vehicle sensor  690  can be coupled to the network switch  125  via an Ethernet cable, and thus can be powered using the electrical power carried over the Ethernet cable. When a vehicle is detected or a certain type of vehicle is detected (e.g., a car, a van, a truck, a motorcycle, etc.), the vehicle sensor  690  can transmit information corresponding to the detection to one or more of the processors  142 N,  142 S,  142 W, and/or  142 E via the network switch  125 . One or more of the processors  142 N,  142 S,  142 W, and/or  142 E can then use the information in a manner similar to as described above with respect to the camera  650  to more efficiently control the flow of traffic. 
     In further embodiments, the improved vehicle traffic signal control system includes an independent conflict monitor that may receive electrical power via one or one or more Ethernet cables coupled to the network switch  125 . For example, each light head  140 N,  140 S,  140 W,  140 E can include one or more current sensors configured to monitor the current passing through one or more of the lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E. The current sensors can transmit status messages to each other, where the status messages indicate which lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E have a current greater than zero (e.g., indicating the respective light  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E is on). If a current sensor determines that two or more green lights  148 N,  148 S,  148 W, and/or  148 E are on that would create a conflict (e.g., green lights perpendicular to each other are both on), then the current sensor can notify one or more of the processors  142 N,  142 S,  142 W, and/or  142 E, and the processors  142 N,  142 S,  142 W, and/or  142 E may then correct the issue (e.g., turning off a conflicting green light) or cause the red lights  144 N,  144 S,  144 W, and/or  144 E to flash. 
     As another example, one or more cameras powered via one or more Ethernet cables can be positioned to face one or more of the lights  144 N,  144 S,  144 W,  144 E,  146 N,  146 S,  146 W,  146 E,  148 N,  148 S,  148 W, and/or  148 E. For example, the camera(s) can be mounted to poles supporting light head(s)  140 N,  140 S,  140 W, and/or  140 E. Images and/or video captured by the camera(s) can be transmitted to one or more processors  142 N,  142 S,  142 W, and/or  142 E, and the processors  142 N,  142 S,  142 W, and/or  142 E can process the images and/or video frames to determine whether a conflict is present. If a conflict is present, the processors  142 N,  142 S,  142 W, and/or  142 E can communicate with each other to correct the issue (e.g., turning off a conflicting green light) or cause the red lights  144 N,  144 S,  144 W, and/or  144 E to flash. 
     In some embodiments, the light heads  140 N,  140 S,  140 W, and/or  140 E can collect traffic data independent of the controller  120 . For example, the light heads  140 N,  140 S,  140 W, and/or  140 E can power cameras used to monitor traffic conditions during different times of the day, week, year, etc. The light heads  140 N,  140 S,  140 W, and/or  140 E (e.g., via the processors  142 N,  142 S,  142 W, and/or  142 E) can transmit the traffic data directly to an historical traffic data collection system via or not via the controller  120 . In typical vehicle traffic signal control systems, any collected traffic data passes through the controller before being forwarded to an historical traffic data collection system. However, transmitting the data via the controller can increase data transmission latency. In addition, the extra step that results from first transmitting the traffic data to the controller provides an additional opportunity for data loss to occur (e.g., via severed wires, power outages, signal interference, etc.). On the other hand, because the light heads  140 N,  140 S,  140 W, and/or  140 E have data processing capabilities, the controller  120  can be bypassed when collecting and transmitting such traffic data, thereby reducing data transmission latency and reducing the likelihood that data loss will occur. 
     Light Control Routine 
       FIG.  7    is a flow diagram depicting a light control routine  700 , according to one embodiment. As an example, a light head  140 N,  140 S,  140 W, and/or  140 E (e.g., a processor  142 N,  142 S,  142 W, and/or  142 E) of FIG. lA can be configured to execute the light control routine  700 . The light control routine  700  begins at block  702 . 
     At block  704 , a light head control message is received. For example, the light head control message may be received from the controller  120 . The light head control message may include rules that define when a light head can enable and/or disable lights. 
     At block  706 , a status message is received from a light head or sensor. For example, the sensor can be a crosswalk button  440 , a camera  650 , a transponder  660 , a vehicle sensor  690 , an IoT device, and/or the like. The status message may indicate a change in the state of a light head or the sensor. 
     At block  708 , a determination is made as to whether a green light condition is present. For example, the green and yellow lights of the light head executing the light control routine  700  may be off and the red light of the light head executing the light control routine  700  may be on. A green light condition may be present, as defined by the rules in the light head control message, if certain red lights are on, certain green and yellow lights are off, and/or certain crosswalks are off. The determination can be made using the received status message and any previously received status messages. If the green light condition is present, then the light control routine  700  proceeds to block  710 . Otherwise, if the green light condition is not present, then the light control routine  700  proceeds back to block  706 . 
     At block  710 , the red light is turned off. In response to turning the red light off or in response to making the determination that the red light should be turned off, the light head can generate and transmit a status message corresponding to the change in state of the red light from on to off. 
     At block  712 , the green light is turned on. For example, the green light can be turned on by allowing electrical power received from the network switch  125  via the Ethernet cable to pass through to the green light. 
     At block  714 , a status message is transmitted to other light heads indicating that the green light is on. The status message can be generated and/or transmitted in response to turning the green light on or in response to making the determination that the green light should be turned on. After transmitting the status message, the light control routine  700  ends, as shown at block  716 . 
     Traffic Signal Retrofit Routine 
       FIG.  8    is a flow diagram depicting a traffic signal retrofit routine, method, or process  800 , according to one embodiment. As an example, a technician, contractor, civil engineer, and/or other similar individual can perform the traffic signal retrofit routine  800  to retrofit an existing intersection to implement the features of the improved vehicle traffic signal control system described herein. The traffic signal retrofit routine  800  begins at block 
     At block  804 , wires in conduit(s) that couple relays to light heads are removed. For example, these wires can include the wires that carry 120VAC from relays to each light head light, the neutral wires, and the ground wires. As an illustrative example, if a light head includes five lights, seven wires are removed from the conduit(s): the 120VAC wire from relay #1 to light #1, the 120VAC wire from relay #2 to light #2, the 120VAC wire from relay #3 to light #3, the 120VAC wire from relay #4 to light #4, the 120VAC wire from relay #5 to light #5, the neutral wire, and the ground wire. If each light head at the intersection includes five lights and there are four light heads total at the intersection, then 28 total wires are removed from the conduit(s). 
     At block  806 , relays are removed. For example, the relays that are removed may be the relays originally used to control whether electrical power is supplied to the various light head lights. In further embodiments, other components are also removed from the traffic signal box, including a conflict monitor. 
     At block  808 , a processor (e.g., a microprocessor) is added to the light heads at the intersection. For example, each light head may be modified to include one or more processors programmed to execute computer-executable instructions that, when executed by the processor(s), cause the processor(s) to perform the operations described herein, including supplying or not supplying electrical power to the light head lights. The computer-executable instructions can be stored in memory also added to each of the light heads, and may be derived from the rules or instructions included in the light head control message. For example, a light head can store the rules or instructions included in the light head control message in the memory once the light head control message is received. The rules or instructions can be stored in the form of computer-executable instructions. The light head processor can then retrieve some or all of the computer-executable instructions from the memory for execution, causing the processor to perform the operations described herein. 
     At block  810 , a network switch is added to the controller. For example, the network switch can be an Ethernet switch. Alternatively, the original controller in the traffic signal box is replaced with another controller that includes a network switch or that is configured to couple to a network switch. 
     At block  812 , an Ethernet cable is routed between the controller and each light head processor via the conduit(s). Thus, the bulky wires originally present in the conduit(s) can be replaced with one or more Ethernet cables. In particular, the bulky wires associated with a single light head originally present in the conduit(s) to couple relays to the associated light head can be replaced with a single Ethernet cable that couples the controller to the light head. As an illustrative example, if a light head includes five lights, seven wires are removed from the conduit(s) and replaced with a single Ethernet cable. After the Ethernet cable(s) are routed between the controller and light heads, the traffic signal retrofit  802  routine ends, as shown at block  814 . 
     As is apparent, the traffic signal retrofit routine  800  allows technicians, contractors, civil engineers, and/or other similar individuals to reuse existing infrastructure (e.g., conduits, poles, etc.) to implement the improved vehicle traffic signal control system. Because existing infrastructure can be reused, the improved vehicle traffic signal control system can be implemented to include a wide variety of technology (e.g., cameras, light emitting diode (LED) lights, Internet-of-Things (IoT) devices, etc.) at a modest upgrade cost. 
     Optionally, a retrofit kit may be provided with some or all of the components and/or instructions necessary to perform the traffic signal retrofit routine  800 . For example, the retrofit kit may include a processor (e.g., processor  142 N,  142 S,  142 W, and/or  142 E) that can be added to a light head (e.g. attached to a light head, installed within a light head, etc.) and be coupled to the various lights in the light head. The retrofit kit can also include an Ethernet cable that can be coupled between the light head and the controller  120 . Thus, the retrofitted light head would, in total, receive 120VAC for each light, neutral, ground, and the Ethernet cable (e.g., the existing wires may not be removed). The processor of the retrofit kit could then be used to control the enabling and/or disabling of the lights in the light head. 
     While the improved vehicle traffic signal control system is described herein primarily with reference to automobiles or other street-capable vehicles, this is not meant to be limiting. The features described herein can be implemented in any type of vehicle traffic control system, such as an air traffic taxiing control system, a train traffic control system, a ship traffic control system, and/or the like. 
     Terminology 
     All of the methods and tasks described herein may be performed and fully automated by a computer system. The computer system may, in some cases, include multiple distinct computers or computing devices (for example, physical servers, workstations, storage arrays, cloud computing resources, etc.) that communicate and interoperate over a network to perform the described functions. Each such computing device typically includes a processor (or multiple processors) that executes program instructions or modules stored in a memory or other non-transitory computer-readable storage medium or device (for example, solid state storage devices, disk drives, etc.). The various functions disclosed herein may be embodied in such program instructions, or may be implemented in application-specific circuitry (for example, ASICs or FPGAs) of the computer system. Where the computer system includes multiple computing devices, these devices may, but need not, be co-located. The results of the disclosed methods and tasks may be persistently stored by transforming physical storage devices, such as solid state memory chips or magnetic disks, into a different state. In some embodiments, the computer system may be a cloud-based computing system whose processing resources are shared by multiple distinct business entities or other users. 
     Depending on the embodiment, certain acts, events, or functions of any of the processes or algorithms described herein can be performed in a different sequence, can be added, merged, or left out altogether (for example, not all described operations or events are necessary for the practice of the algorithm). Moreover, in certain embodiments, operations or events can be performed concurrently, for example, through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. 
     The various illustrative logical blocks, modules, routines, and algorithm steps described in connection with the embodiments disclosed herein can be implemented as electronic hardware (for example, ASICs or FPGA devices), computer software that runs on computer hardware, or combinations of both. Moreover, the various illustrative logical blocks and modules described in connection with the embodiments disclosed herein can be implemented or performed by a machine, such as a processor device, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A processor device can be a microprocessor, but in the alternative, the processor device can be a controller, microcontroller, or state machine, combinations of the same, or the like. A processor device can include electrical circuitry configured to process computer-executable instructions. In another embodiment, a processor device includes an FPGA or other programmable device that performs logic operations without processing computer-executable instructions. A processor device can also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. Although described herein primarily with respect to digital technology, a processor device may also include primarily analog components. For example, some or all of the rendering techniques described herein may be implemented in analog circuitry or mixed analog and digital circuitry. A computing environment can include any type of computer system, including, but not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a device controller, or a computational engine within an appliance, to name a few. 
     The elements of a method, process, routine, or algorithm described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor device, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of a non-transitory computer-readable storage medium. An exemplary storage medium can be coupled to the processor device such that the processor device can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor device. The processor device and the storage medium can reside in an ASIC. The ASIC can reside in a user terminal. In the alternative, the processor device and the storage medium can reside as discrete components in a user terminal. 
     Conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” “for example,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements or steps. Thus, such conditional language is not generally intended to imply that features, elements or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without other input or prompting, whether these features, elements or steps are included or are to be performed in any particular embodiment. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations, and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some, or all of the elements in the list. 
     Disjunctive language such as the phrase “at least one of X, Y, or Z,” unless specifically stated otherwise, is otherwise understood with the context as used in general to present that an item, term, etc., may be either X, Y, or Z, or any combination thereof (for example, X, Y, or Z). Thus, such disjunctive language is not generally intended to, and should not, imply that certain embodiments require at least one of X, at least one of Y, and at least one of Z to each be present. 
     While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it can be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the spirit of the disclosure. As can be recognized, certain embodiments described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others. The scope of certain embodiments disclosed herein is indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.