Multimode traffic priority/preemption intersection arrangement

FIELD OF THE INVENTION

The present invention is generally directed to systems and methods that allow traffic light systems to be remotely controlled using data communication, for example, involving optical pulse transmission from an optical emitter to an optical detector that is communicatively-coupled to a traffic light controller at an intersection.

BACKGROUND OF THE INVENTION

Traffic signals have long been used to regulate the flow of traffic at intersections. Generally, traffic signals have relied on timers or vehicle sensors to determine when to change the phase of traffic signal lights, thereby signaling alternating directions of traffic to stop, and others to proceed.

Emergency vehicles, such as police cars, fire trucks and ambulances, are generally permitted to cross an intersection against a traffic signal. Emergency vehicles have typically depended on horns, sirens and flashing lights to alert other drivers approaching the intersection that an emergency vehicle intends to cross the intersection. However, due to hearing impairment, air conditioning, audio systems and other distractions, often the driver of a vehicle approaching an intersection will not be aware of a warning being emitted by an approaching emergency vehicle.

There are presently a number of optical traffic priority systems that permit emergency vehicles to preempt the normal operation of the traffic signals at an intersection in the path of the vehicle to permit expedited passage of the vehicle through the intersection. These optical traffic priority systems permit a code to be embedded into an optical communication to identify each vehicle and provide security. Such a code can be compared to a list of authorized codes at the intersection to restrict access by unauthorized users. However, the various optical traffic priority systems are incompatible because the vehicle identification code for each of the various optical traffic priority systems is embedded in the optical communication using incompatible modulation schemes.

Generally, an optical traffic priority system using a particular modulation scheme is independently purchased and implemented in each jurisdiction, such as a city. Thus, the traffic lights and the emergency vehicles for the jurisdiction are equipped to use the particular modulation scheme. However, a neighboring jurisdiction may use equipment that embeds the vehicle identification code using an incompatible modulation scheme. Frequently, a pursuit by a police car or the route of an ambulance may cross several jurisdictions each using an incompatible modulation scheme to embed the vehicle identification information. It may be burdensome and expensive to allow a vehicle from a neighboring jurisdiction to preempt traffic lights while maintaining appropriate security to prevent unauthorized preemption of traffic lights.

SUMMARY OF THE INVENTION

The present invention is directed to overcoming the above-mentioned challenges and others that are related to the types of approaches and implementations discussed above and in other applications. The present invention is exemplified in a number of implementations and applications, some of which are summarized below.

In connection with one embodiment, the present invention is directed to implementations that allow traffic light systems to be remotely controlled using multiple communication modes.

In a more particular embodiment, a traffic light control system includes at least one parameter and a signal decoding circuit. The parameter or parameters are useful for assisting in differentiating between multiple communication modes. The signal decoding circuit has a front-end circuit and a back-end circuit. The front-end circuit is adapted to receive respective signals transmitted in multiple communication modes. The front-end circuit is adapted to produce data representative of at least a portion of the respective signals. The back-end circuit is adapted to interpret and process the produced data according to at least one of multiple traffic light control protocols respectively associated with the multiple communication modes. The signal decoding circuit is adapted to access the at least one parameter and associate the produced data with one of the multiple communication modes.

The above summary of the present invention is not intended to describe each illustrated embodiment or every implementation of the present invention. The figures and detailed description that follow more particularly exemplify these embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention is believed to be applicable to a variety of different communication modes in an optical traffic preemption system. While the present invention is not necessarily limited to such approaches, various aspects of the invention may be appreciated through a discussion of various examples using these and other contexts.

The optical traffic preemption system shown inFIG. 1is presented at a general level to show the basic circuitry used to implement example embodiments of the present invention. In this context,FIG. 1illustrates a typical intersection10having traffic signal lights12. A traffic signal controller14sequences the traffic signal lights12through a sequence of phases that allow traffic to proceed alternately through the intersection10. The intersection10is equipped with an optical traffic preemption system having certain aspects and features enabled in accordance with the present invention to support multiple communication modes in an efficient, flexible and practicable manner.

This support for multiple communication modes is provided in the optical traffic preemption system ofFIG. 1by way of optical emitters24A,24B and24C, detector assemblies16A and16B, and a phase selector18. The detector assemblies16A and16B are stationed to detect light pulses from optical emitters24A,24B and24C mounted on authorized vehicles approaching the intersection10. The detector assemblies16A and16B communicate with the phase selector18, which is typically located in the same cabinet as the traffic controller14.

InFIG. 1, an ambulance20and a bus22are approaching the intersection10. The optical emitter24A is mounted on the ambulance20and the optical emitter24B is mounted on the bus22. The optical emitters24A and24B each transmit a stream of light pulses. The stream of light pulses can transport data values that identify a requested operation, such as preemption of the normal operation of the traffic lights12to allow expedited passage of the vehicle20or22through the intersection10. The detector assemblies16A and16B receive these light pulses and send an output signal to the phase selector18. The phase selector18processes and validates the output signal from the detector assemblies16A and16B.

The optical emitters24A and24B can use incompatible communication modes and modulation schemes to embed the data values in the stream of light pulses. Various embodiments of the invention provide extraction and validation of the data values embedded in the stream of light pulses by the detector assemblies16A and16B and the phase selector18, regardless of the communication mode used by a particular emitter24A or24B. After extraction and successful validation of a requested operation, the phase selector18can issue a phase request to the traffic signal controller14to preempt the normal operation of the traffic signal lights12.

FIG. 1also shows an authorized person21operating a portable optical emitter24C, which is there shown mounted to a motorcycle23. In one embodiment, the emitter24C is used to configure parameters of the detector assemblies16A and16B and/or phase selector18, including parameters used to differentiate the various communication modes and to validate data values embedded in the stream of light pulses according to multiple traffic light control protocols respectively associated with the multiple communication modes. In another embodiment, the emitter24C is used by the authorized person21to affect the traffic signal lights12in situations that require manual control of the intersection10.

Typically, the data values for a requested operation include a vehicle identification code. Phase selectors constructed in accordance with the present invention can be configured to use a vehicle identification code in various ways. In one configuration, the phase selector18is configured with parameters providing a list of authorized identification codes. In this configuration, the phase selector18confirms that the vehicle is indeed authorized to preempt the normal traffic signal sequence. If the received vehicle identification code does not match one of the authorized identification codes on the list, preemption does not occur. In another configuration, the phase selector18is configured with parameters specifying limits for a range of values of authorized identification codes, possibly with separate ranges for emergency vehicles20and mass transit vehicles22. If the received vehicle identification code is not within the appropriate range of values, preemption does not occur.

In yet another configuration, the phase selector18logs all preemption requests by recording the time of preemption, direction of preemption, duration of preemption, identification code, confirmation of passage of a requesting vehicle within a predetermined range of a detector, and denial of a preemption request due to improper authorization. In this configuration, attempted abuse of an optical traffic preemption system can be discovered by examining the logged information.

In another embodiment of the present invention, an optical traffic preemption system helps run a mass transit system more efficiently. An authorized mass transit vehicle having an optical emitter constructed in accordance with the present invention, such as the bus22inFIG. 1, spends less time waiting at traffic signals, thereby saving fuel and allowing the mass transit vehicle to serve a larger route. This also encourages people to utilize mass transportation instead of private automobiles because authorized mass transit vehicles move through congested urban areas faster than other vehicles.

Unlike an emergency vehicle, a mass transit vehicle equipped with an optical emitter may not require total preemption. In one embodiment, a traffic signal offset is used to give preference to a mass transit vehicle, while still allowing all approaches to the intersection to be serviced. For example, a traffic signal controller that normally allows traffic to flow 50 percent of the time in each direction responds to repeated phase requests from the phase selector to allow traffic flowing in the direction of the mass transit vehicle to proceed 65 percent of the time and traffic flowing in the other direction to flow 35 percent of the time. In this embodiment, the actual offset is fixed to allow the mass transit vehicle to have a predictable advantage. Generally, proper authorization should be validated before executing an offset for a mass transit vehicle.

In a typical installation, the traffic preemption system does not actually control the lights at a traffic intersection. Rather, the phase selector18alternately issues phase requests to and withdraws phase requests from the traffic signal controller14, and the traffic signal controller determines whether the phase requests can be granted. The traffic signal controller may also receive phase requests originating from other sources, such as a nearby railroad crossing, in which case the traffic signal controller may determine that the phase request from the other source be granted before the phase request from the phase selector. However, as a practical matter, the preemption system can affect a traffic intersection and create a traffic signal offset by monitoring the traffic signal controller sequence and repeatedly issuing phase requests that will most likely be granted.

According to a specific example embodiment, the traffic preemption system ofFIG. 1is implemented using a known implementation that is modified to support multiple communication modes. For example, an Opticom™ Priority Control System (manufactured by 3M Company of Saint Paul, Minn.) can be modified to support one or more communication modes in addition to the communication mode for the Opticom™ Priority Control System. Consistent with features of the Opticom™ Priority Control System, one or more embodiments of U.S. Pat. No. 5,172,113 can be modified in this manner. Also according to the present invention, another specific example embodiment is implemented using another commercially-available traffic preemption system, such as the Strobecom II system (manufactured by TOMAR Electronics, Inc. of Phoenix, Ariz.), modified to support one or more additional communication modes.

FIG. 2A-2Cillustrate optical pulses transmitted between a vehicle and equipment at an intersection for various example communication modes in accordance with the present invention. A first communication mode as illustrated inFIG. 2A, can have optical pulse stream100. A second communication, as illustrated inFIG. 2B, mode can have optical pulse stream120. A third communication mode, as illustrated inFIG. 2C, can have optical pulse stream140that combines the features of optical pulse streams100and120.

Optical pulse stream100has major stroboscopic pulses of light102occurring at a particular frequency that typically is nominally either 10 Hz or 14 Hz. Between the major pulses, optional data pulses104,106, and108carry the data values embedded in the optical pulse stream100. For example, if pulse104is present then a data value has a first bit of one, and if pulse104is absent then the data value has a first bit of zero. If pulse106is present then the data value has a second bit of one, and if pulse106is absent then the data value has a second bit of zero. Similarly, if pulse108is present then the data value has a third bit of one, and if pulse108is absent then the data value has a third bit of zero. Typically, the optional pulses104,106, and108are half-way between the major pulses102. Optical pulse stream100may correspond to the communication mode of an Opticom™ Priority Control System.

Optical pulse stream120has stroboscopic pulses of light that nominally occur at a particular frequency that typically is approximately either 10 Hz or 14 Hz, but the pulses are displaced from the nominal frequency to embed the data values in the optical pulse stream120. For example, after an initial pulse122, only one or the other of pulses124and126is present and if an early pulse124is present then a data value has a first bit of zero and if late pulse126is present then the data value has a first bit of one. Only one or the other of pulses128and130is present and if early pulse128is present then the data value has a second bit of zero and if late pulse130is present then the data value has a second bit of one. Similarly, only one or the other of pulses132and134is present and if early pulse132is present then the data value has a third bit of zero and if late pulse134is present then the data value has a third bit of one.

Another optical pulse stream is similar to optical pulse stream120in having stroboscopic pulses of light that nominally occur at a particular frequency that typically is approximately either 10 Hz or 14 Hz, with the pulses displaced from the nominal frequency to embed the data values in the optical pulse stream120. However, each pulse is separated from the prior pulse with a nominal time period corresponding to the nominal frequency with the actual separation between a pulse and the prior pulse being slightly less or slightly more than the nominal time period. An early pulse with a separation from the prior pulse of slightly less than the nominal time period embeds a data bit of zero and a late pulse with a separation from the prior pulse of slightly more than the nominal time period embeds a data bit of one. Such an optical pulse stream may correspond to the communication mode of a Strobecom II system.

Optical pulse stream140combines the possible pulse positions of optical pulse streams100and120, providing the benefit that more data values can be embedded in the pulse stream in a given time period. The additional data can be used to provide additional operations, to enhance the security using encryption, and/or enhance robustness by adding error detection or correction without increasing the response time of the optical traffic control system. After the initial pulse142, the presence or absence of pulse144respectively provides a first bit of one or zero. Only one of pulses146,150, and148is present in pulse stream140. The presence of pulse146provides a second bit of zero and the presence of pulse148provides a second bit of one. The presence of pulse150could indicate that the second bit does not have a value or the second bit has an unknown value. Additional bits including a third bit through the sixth bit are similarly embedded.

It will be appreciated that an optical pulse stream similar to stream140can combine the possible pulse positions of pulse stream100and a second optical pulse stream that embeds data values by shifting the time period between each pulse and the prior pulse slightly from the nominal time period. Such a combined pulse stream can position the intermediate pulses104,106, and108of stream100halfway between the slightly shifted pulses that are substituted for pulses102of stream100.

A detection circuit arranged to extract the embedded data values for optical pulse stream140has the advantage of supporting a higher data communication rate and being compatible with both optical pulse streams100and120. After receiving an optical pulse stream140and extracting the embedded data value, a data value with any of the second, fourth, and sixth bits having an unknown value, as indicated by the presence of a pulse150,152, or154, corresponds to optical pulse stream100. None of the second, fourth, and sixth bits having an unknown value, as indicated by the absence of pulses150,152, and154, and any of the first, third, and fifth bit having a value of a one, as indicated by the presence of a pulse144,156, or158, corresponds to pulse stream140. None of the second, fourth, and sixth bits having an unknown value and none of the first, third, and fifth bits having a value of a one, as indicated by the absence of pulses144,156, and158, can correspond to pulse stream120. Thus, not only can the embedded data be extracted for either of optical pulse streams100and120by a detection circuit supporting optical pulse stream140, in addition the pulse streams100,120, and140can be readily distinguished.

The nominal frequency used to transmit pulses of an optical pulse stream100,120, and140can determine a priority. For example, a frequency of approximately 10 Hz can correspond to a high priority for an emergency vehicle and a frequency of approximately 14 Hz can correspond to a low priority for a mass transit vehicle.

FIG. 3is a block diagram showing the optical traffic preemption system ofFIG. 1. InFIG. 3, light pulses originating from the optical emitters24A and24B are received by the detector assembly16B, which is connected to a channel one and channel two of the phase selector18. The main processor40of phase selector18communicates with the traffic signal controller14, which in turn controls the traffic signal lights12.

In one embodiment, detector assembly16B is a front-end circuit receiving signals from emitters24A and24B having respective communication modes. Signal processing circuitry36A and36B and processors38A,38B, and40are a back-end circuit that interprets and processes data produced by the detector assembly16B from the received signals. Channel one signal processing circuitry36A and processor38A can interpret and process the data according to a traffic light control protocol corresponding to the communication mode of emitter24A and channel two signal processing circuitry36B and processor38B can interpret and process the data according to a traffic light control protocol corresponding to the communication mode of emitter24B. It will be appreciated that protocols for multiple communication modes may be interpreted and processed in various embodiments with a single signal processing channel as is discussed in connection withFIG. 4. Circuits16B,36A,36B,38A,38B, and40may operate using parameters stored internally to the respective circuit or stored in long term memory42and some of these parameters can be useful for differentiating between the communication modes of emitters24A and24B by the respective channel.

In another embodiment, detector assembly16B and signal processing circuitry36A and36B are a front-end circuit receiving signals from emitters24A and24B having respective communication modes. Processors38A,38B, and40are a back-end circuit that interprets and process data from the signal processing circuitry36A and36B. Processor38A can interpret and process the data according to a traffic light control protocol corresponding to the communication mode of emitter24A and processor38B can interpret and process the data according to a traffic light control protocol corresponding to the communication mode of emitter24B. Circuits16B,36A,36B,38A,38B, and40may operate using parameters stored internally to the respective circuit or stored in long term memory42and some of these parameters can be useful for differentiating between the communication modes of emitters24A and24B by the processors38A,38B, and40.

The phase selector18includes the two channels, with each channel having signal processing circuitry (36A and36B) and a processor (38A and38B), a main processor40, long term memory42, an external data port43and a real time clock44. With reference to the channel one, the signal processing circuitry36A receives an analog signal provided by the detector assembly16B. The signal processing circuitry36A processes the analog signal and produces digital data that is received by the channel processor38A. The channel processor38A extracts the embedded data value from the digital data and provides the data value to the main processor40. Channel two is similarly configured, with the detector assembly16B coupled to the signal processing circuitry36B, which in turn is coupled to the channel processor38B. Each channel is dedicated to interpreting and processing data according to a respective traffic signal control protocol. It will be appreciated that channel two may process the received signal either in parallel with channel one or after channel one has determined that the received signal is not recognized as corresponding to the communication mode of channel one.

The long term memory42is implemented using electronically erasable programmable read only memory (EEPROM). The long term memory42is coupled to the main processor40and is used log data and to store configuration parameters and a list of authorized identification codes. The main processor40checks for proper authorization by checking that the received vehicle identification code matches an entry in a list authorized identification.

The external data port43is used for coupling the phase selector18to a computer. In one embodiment, external data port43is an RS232 serial port. Typically, portable computers are used in the field for exchanging data with and configuring a phase selector with parameters. Logged data is removed from the phase selector18via the external data port43and parameters and a list of authorized identification codes are stored in the phase selector18via the external data port43. The external data port43can also be accessed remotely using a modem, local-area network or other such device.

The real time clock44provides the main processor40with the actual time. The real time clock44provides time stamps that can be logged to the long term memory42and is used for timing other events, such as providing a time tag associated with each light pulse received at detector assembly16B.

FIG. 4is a block diagram of the components of an optical traffic preemption system for another embodiment in accordance with the present invention. Light pulses originating from the optical emitters24A and24B are received by the detector assembly16B, which is connected to phase selector18. Phase selector18supports multiple communication modes having corresponding traffic light control protocols. For example, optical emitter24A can use one communication mode, optical emitter24B can use another communication mode, and phase selector18can support both emitters24A and24B including extracting data values embedded in the optical pulse streams received from emitters24A and24B. Phase selector18includes a decoder160, a database162and an external port163.

Database162includes parameters to configure the operation of the decoder160including a single table164in one embodiment and multiple tables164and166in another embodiment. A single table164can include information for multiple communication modes. For example, even though different modulation schemes are used to embed a vehicle identification code for two communication modes, a single set of identification codes for both communication modes can be maintained in the table164. For another example, table164can include identification codes for one communication mode and table166can include identification codes for another communication mode.

Database162can also include logs168of preemption activity. For example, each successful and unsuccessful preemption request received can be logged in logs168, including the vehicle identification code for the preemption request and the communication mode used to make the preemption request. An external port163provides access to the database162including downloading and erasing the logs168and updating the mode tables164and166.

Front-end circuit170can include a sampling analog to digital converter (ADC) and a digital signal processor (DSP). The ADC may have configurable parameters, such as sampling rate, and the DSP can have configurable parameters, such as filter software routines, that are provided by database162. Serially produced data from front-end circuit170can be stored in memory172. Memory172can temporarily store the serial data stream until one or more complete operation requests are available for processing by back-end circuit174and until the discriminator176determines the communication mode being used using various distinguishing characteristics of the communication modes. Using the communication mode from discriminator176, the back-end circuit174extracts the data values embedded in the optical pulse stream. The back-end circuit174validates the operation request in the data values according to the traffic light control protocol corresponding to the communication mode.