Background of the Invention Various systems have been proposed to inform travelers of traffic hazards.

Jackson, U. S. Patent No. 5,235,329, is directed to a fleet of emergency vehicles, and to a system for permitting each of the emergency vehicles to warn each other, as well as warn other vehicles in the vicinity, of their presence.

Barsh, et. al., U. S. Patent No. 3,673,560, similarly discloses a system for alert- ing persons in vehicles of the presence of emergency vehicles. According to this system, each emergency vehicle has a transmitter and a receiver. Each transmitter has an encoder which produces a signal having a duty cycle comprising a series of 15 kHz pulses for a period of approximately 0.5 sec., followed by a period of no pulses for approximately one second. This signal is transmitted at a modulated frequency of 150 MHz. Each receiver has a detector which is deactivated during the transmission of the 15 kHz signals, so as not to detect transmission of its own signal.

Grosser et al., U. S. Patent No. 3,772,641, discloses a self-testing emergency automotive warning system for an emergency vehicle to warn drivers of nearby vehicles. The emergency signal is at 10 mHz, and use of the system in conduction with stationary situations, such as unsafe bridges, tunnels, road construction, etc., is also disclosed.

Bishop, U. S. Patent No. 4,443,790 discloses an alarm for an emergency vehicle which transmits a broadcast band carrier wave which has been modulated with a

siren signal and voice signal. The carrier frequency is swept over both an AM and FM broadcast band for detection of conventional radio receivers.

Halstead, U. S. Patent No. 4,794,394, discloses an emergency vehicle proximity warning system. An emergency vehicle transmits a continuous series of pulses. A second vehicle has a receiver which receives the pulses. Upon detection of the pulses, the receiver interrupts the connection between the radio and speaker of the second vehicle, and energizes lamps and/or sound-issuing devices within the second vehicle.

Summary of the Invention It is an object of the invention to provide a transportation information warning system for conveying information from a traffic advisory site to a traveler. The traffic warning site comprises an emergency vehicle, a roadside hazard, or the like.

In accordance with the invention, the system comprises a transmitter adapted for placement at the advisory site and a receiver adapted for placement with a receiving station.

The transmitter includes means for transmitting a first unmodulated carrier signal at a first frequency and means for transmitting a second unmodulated carrier signal at a second frequency. The first and second frequencies define the traffic information.

The receiver includes means for detecting the first and second signals, means responsive to the detecting means for determining the traffic information and means responsive to the determining means for announcing the traffic information.

It is contemplated that the announcing means includes a visual display, an audible, or both.

In one embodiment, the receiver determines the traffic information by determining the magnitude of the frequency difference between the first and second frequencies.

In another embodiment, the receiver determines the traffic information by determining the specific frequency locations of the first and second frequencies.

It is further contemplated that the transmitter can include means for selectively transmitting one of a plurality of second unmodulated carrier signals, to selective transmission of a plurality of traffic information messages.

It is further contemplated that the transmitter can be placed in a number of different locations to notify travelers of many different types of traffic information.

Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawing.

Brief Description of the Drawings It is an object of the invention to provide a transportation information warning system for conveying information from a traffic advisory site to a traveler. The traffic warning site comprises an emergency vehicle, a roadside hazard, or the like.

In accordance with the invention, the system comprises a transmitter adapted for placement at the advisory site and a receiver adapted for placement with a receiving station.

The transmitter includes means for transmitting a first unmodulated carrier signal at a first frequency and means for transmitting a second unmodulated carrier signal at a second frequency. The first and second frequencies define the traffic information.

The receiver includes means for detecting the first and second signals, means responsive to the detecting means for determining the traffic information and means responsive to the determining means for announcing the traffic information.

It is contemplated that the announcing means includes a visual display, an audible, or both.

In one embodiment, the receiver determines the traffic information by determining the magnitude of the frequency difference between the first and second frequencies.

In another embodiment, the receiver determines the traffic information by determining the specific frequency locations of the first and second frequencies.

It is further contemplated that the transmitter can include means for selectively transmitting one of a plurality of second unmodulated carrier signals, to selective transmission of a plurality of traffic information messages.

It is further contemplated that the transmitter can be placed in a number of different locations to notify travelers of many different types of traffic information.

Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawing.

Detailed Description While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail, preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiments illustrated.

A transportation information warning system, generally designated 10, for con- veying traffic information from a traffic advisory site, such as an emergency vehicle 12 or a roadside hazard 14, to a vehicle 16 is illustrated in Figure 1. The transportation information warning system 10 is generally described in U. S. Patent No. 5,497,148.

As shown in Figure 2, the system 10 comprises a transmitter 18 adapted for placement at the advisory site, such as inside the emergency vehicle 12 or alongside the roadside hazard 14. The system 10 further comprises a receiver 20 adapted for placement inside the emergency vehicle 12.

The transmitter 18 includes a first oscillator 22 for transmitting a first unmodu- lated carrier signal s, at a first frequency and a second oscillator 24 for transmitting a second unmodulated carrier signal at a second frequency s2. The first and second frequencies sl, S2 together define the traffic information, although the invention contemplates various methods for encoding the information, discussed below.

The receiver 20 detects the first and second signals and responds to the detected signals to determine the traffic information. The receiver 20 then an- nounces the traffic information. The announcement may be via a visual display 21, such as a conventional LCD display, an audible display 22, a vibrational response (not shown), or any combination of these. If an audible display, the message could be announced as a tone, which tone would have a pre-arranged and defined meaning for the traveler. Alternatively, the audible message could be a stored voice message, as is well known.

For purposes of discussion, the first signal can be referred to as a reference sig- nal. One such reference signal contemplated is 24.230 GHz., which is in the K- band. The second signal would be one of various other signal frequencies, depending upon the particular traffic information. It is contemplated that if the hazard is an emergency vehicle, the second signal frequency would be 24.11 GHz.

It is further contemplated that if the hazard is a roadside hazard, the second signal frequency would be 24.07 GHz. In the event the hazard is a railroad, the reference signal frequency is contemplated to be 24.19 GHz and the second signal frequency would be 24.11 GHz. It should be apparent that any particular frequency could be utilized without departing from the scope of the invention.

Two receiver modes are contemplated for decoding the signal. According to the first mode, the receiver detects the magnitude of the frequency difference between the first and second frequencies. For example the receiver could include scanning circuitry to scan across the frequencies of interest, and the receiver

"looks"for two signals separated by a predetermined frequency difference. For example, the magnitude of the difference between the reference signal and the roadside hazard signal is 160 MHz. Thus if the receiver detects two signals spaced by 160 MHz, it determines this to represent a roadside hazard, and alarms accordingly. As is well known, the difference can be determined by utilizing a receiver with a constant sweep rate, and measuring the time between the two frequency detections.

According to the second mode, the receiver 20 looks for the presence of signals located at specific frequency locations. With the above example, the receiver 20 would specifically look for one signal at 24.230 GHz and another signal at 24.07 GHz.

The receiver 20 could also be used to detect conventional police radar signals.

However, because of its significant function to detect and warn of traffic hazards and the like, the receiver 20 ignores police radar signals in the event traffic hazard signals are detected.

It is further contemplated that a single receiver could operate to detect and distinguish any of the various signals, such that a single receiver could warn the operator of a vehicle of any of the traffic hazards, or of such other information as the situation warrants.

Transmitters 18 of the type described above can be placed at any number of traffic advisory sites. For instance, locomotives, bicycles, school buses, airplanes, snow removal equipment, and/or paint striping vehicles can be equipped with a transmitter 18 to signal a receiving station having a receiver 20 which is capable of distinguishing between the different traffic advisory sites.

It is further contemplated that the traffic advisory site could be located at a fixed location. For instance, transmitters 18 can be located at construction sites on solar powered sign boards. This type of arrangement could be used to warn

motorists that construction workers are present. Transmitters 18 can also be placed at school zones, such as mounted on school zone crossing signs, and activated upon activation of school zone crossing zone lights, to warn motorists that children are present. In marine applications, transmitters 18 could be placed at boat docks or in lighthouses to direct, guide, or warn marine vehicles having appropriate receivers.

Likewise, the receiving station could be located at a fixed location. For example, a receiver 20 can be placed at a traffic light system. In this example, the receiver 20 could trigger the traffic light system to change all the traffic lights an intersection to change to red, so traffic in all directions would stop. Thus, an emergency vehicle equipped with a transmitter 18 could pass safely through the intersection as all traffic is stopped.

Another example of the receiving station being located at a fixed location is when the receiver 20 is placed in a home. The receiver can be placed in the home to signal the arrival of a school bus, having an appropriate transmitter or the like.

This would allow a prospective passenger to wait in the comfort of their home rather than having to wait at a bus stop.

It is still further contemplated that the transportation information warning system may comprise a single unit having both a transmitter 18 and a receiver 20.

For example, if mounted on a school bus, it could transmit a signal to signal the arrival of the bus and it could receive signals, such as from emergency vehicles, trains, or the like. In addition, the transportation information warning system can be coupled with a citizens'band radio, a car stereo, or an electronic compass to provide a visual and/or audible alarm.

Finally, it is contemplated that the transmitter 18 and the receiver 20 can be programmable. This would allow the user to change warning messages and/or remotely change the transmitted signal.

In a further embodiment illustrated in Figure 4, the transmitter 18 is located within a vehicle 30 which has a hazard notification control. The hazard notification control is generally adapted to activate the vehicle's 30 hazard lights (i. e., emergency flashers) 32 when the vehicle 30 is in distress. The transmitter 18 is electrically and/or mechanically connected to the hazard notification control so that when the control system is triggered, the transmitter 10 begins to emit the first and second signals S,, S2.

Activation of the hazard lights 32 is normally accomplished through human intervention; however, it should be apparent that any particular method of activating the hazard notification control could be utilized without departing from the scope of the invention.

This device provides the driver with additional safety when he/she is in a potentially hazardous situation such as changing a tire on a busy street or being the victim of a traffic accident. The transmitter 18 sends a warning signal that notifies other vehicles of the driver in distress. This system can also be used to summon medical help or roadside assistance. This can be accomplished by having a receiving station located at a fixed location. For example, a receiver can be placed at a hospital, clinic, highway garage, or police station. The transmitter 10 can be programmable to allow the user to change warning messages and/or remotely change the transmitted signal. This device can be retrofit in a vehicle with an existing hazard notification control system.

It will be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein.