Communications: electrical – Override of traffic control indicator by command transmitter
Reexamination Certificate
1999-08-05
2001-05-15
Trieu, Van T. (Department: 2736)
Communications: electrical
Override of traffic control indicator by command transmitter
C340S902000, C340S907000
Reexamination Certificate
active
06232889
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to systems and methods for preempting traffic signals. More particularly, the present invention relates to systems and methods allowing emergency and other vehicles to control or preempt traffic signals.
2. Present State of the Art
Cities and communities are in a continual state of change. Some communities are experiencing tremendous growth, while others are attempting to attract new businesses. Additionally, each city or community is faced with a variety of problems including the problem of developing an adequate transportation system.
The scope of the transportation system is quite broad and includes topics from road construction to mass transit. One primary concern of the transportation system is the road or street system, which must be capable of handling the traffic of a community. Practically all drivers are aware of the delays caused by rush hour, construction, and signal lights. These delays can cause many problems for everyone, especially emergency vehicles.
In addition to the delays, there are different types of roads which have distinct purposes. Main roads are designed to handle large volumes of traffic, while roads built in the suburbs and residential neighborhoods, on the other hand, are different in that they are designed for slow careful driving. In short, the roads of a community are built with a variety of different concerns and purposes in mind.
Regardless of how the roads are built, the traffic on those roads must be controlled, and one method of controlling the traffic on the roads and streets of a community is to use signal lights. Many signal lights are designed with a timing mechanism. With timed signal lights, vehicles wait a certain amount of time before they are presented with a green light, at which point they proceed through an intersection. At intersections with timed signal lights, it is possible for a vehicle to be the only vehicle at the intersection, yet the vehicle must wait for the timer to expire before the signal light presents them with a green light
Today, many signal lights are being replaced or upgraded and have the ability to sense the presence of a vehicle. The advantage of these signal lights is that they can respond to actual traffic conditions. For example, at a signal light with a turn signal, the traffic light can sense when there are no more vehicles turning. When this condition is sensed, the turn signal is deactivated while other lights are activated so that other vehicles, which were waiting to enter the intersection, may proceed.
While these signal lights have improved the control and the flow of traffic, they cannot respond effectively to emergency vehicles which may need to cross or enter the intersection immediately. As a result, an emergency and other vehicles may be delayed behind traffic while waiting for the light to change.
There are many instances where it is imperative that an emergency vehicle proceed through an intersection quickly. In many accidents, time is critical and an ambulance that has green lights at intersections will be able to arrive much quicker. Police cars involved in high speed chases can prevent potentially fatal injuries by controlling the intersections through which the chase is occurring. Police cars will also be able to arrive at crime scenes faster. If the lights of an intersection are controlled or preempted, persons not hearing the sirens of an emergency vehicle are prevented from entering the intersection being preempted. In short, the public can greatly benefit by permitting emergency or other approved vehicles to control or preempt signal lights.
Several attempts have been made to address this issue. One method includes the use of optical devices to transmit the message that a vehicle is requesting a light change or preemption. This method requires that an optical device be mounted on each signal mast for each direction. This can be quite expensive and requires that the optical device and the corresponding emergency vehicle be able to see each other. Other systems employ the use of global positioning technology. This method has significant drawbacks, even though it may be effective. For instance, the system requires extensive programming, not only for the emergency vehicles, but also for the location of each intersection. Also, the position of the vehicle must constantly be reevaluated. Other methods require that a highly directional transmit or receive antenna be mounted for each direction of travel in addition to the transmit antenna in the vehicle.
OBJECT AND SUMMARY OF THE INVENTION
It is therefore an object of one embodiment of the present invention to discriminate the direction of travel of a vehicle.
It is another object of one embodiment of the present invention to preempt the normal operation of a signal light.
It is a further object of one embodiment of the present invention to allow emergency vehicles to preempt signal lights.
It is an additional object of one embodiment of the present invention to permit emergency and other types of vehicles to navigate intersections more easily.
It is yet another object of one embodiment of the present invention to permit other types of vehicles, such as mass transit vehicles, to preempt signal lights.
It is a further object of one embodiment of the present invention to control the operation of signal lights at an intersection.
In summary, the present invention assists emergency and other vehicles to proceed through an intersection quickly and easily by preempting the signal lights of an intersection. This is accomplished in one embodiment by installing a base unit at each intersection to be controlled and preempted. The base unit connects to the signal light in a manner that permits the controller to control which lights are green and which lights are red when an emergency vehicle needs to proceed through the intersection. More specifically, the base unit provides a group of control signals which may be used to decide which lights should be green and which lights should be red. The use of the control signals by the signal lights is a decision made by the relevant authority. In one embodiment, a green light is presented to the operator of the emergency vehicle when an appropriate signal is received from an emergency or other vehicle. In another embodiment, all signal lights are turned red when an appropriate signal is received from an emergency or other vehicle. In other words, the status of the signal lights depends in part on: the type of vehicle seeking to preempt the signal lights; and how the relevant authority desires the signal lights to respond to the control signals.
The signal sent to the base unit at the intersection is generated by a mobile unit, which is located in each vehicle which needs the capability to preempt or control signal lights. The mobile unit determines the direction of travel of the vehicle by measuring the magnetic heading. This heading is transmitted to the base unit, where it is processed to take into account the physical orientation of the intersection. Next, the base unit produces output signals which permit the normal operation of the signal lights to be controlled such that the signal lights are preempted by the vehicle and a green light is presented to the vehicle.
The transmission of the magnetic heading to the base unit is accomplished using a transmitter operating at a high frequency. The high frequency and controlled attenuation of the transmitted signal essentially limits the range of the transmission such that only the intersection that the vehicle is approaching and will be passing through is preempted by the vehicle. However, the range of the transmission can be extended or shortened as needed. In this manner, an emergency or other vehicle can more easily pass through intersections without interrupting the traffic flow at other intersections.
The present invention is not limited to emergency vehicles. Other types of vehicles can also preempt signal lights, if they are permitted to do so by the relevant authority.
Apitz Peter
Dyer Emery B.
LandOfFree
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