Emergency vehicles, such as fire-fighting vehicles, ambulances, and police cars, generally have the need to cross or pass through traffic signal control intersections in the shortest time possible in order to arrive at the site of an emergency in a timely manner. Even seconds can be critical to saving lives. In fact it is well known that the chances of survival of an emergency victim are considerably increased by the speed with which the emergency aid is administered.
When emergency vehicles normally proceed through an intersection they depend upon sirens, horns, bells, flashing lights or some other type of audible or visible alarm from the emergency vehicle to alert other vehicles and pedestrians in the area as to their approach Often however, due to confusion, impaired hearing, inattention, noise conditions, etc., serious accidents have occurred at these intersections due to the fact that drivers or pedestrians on the cross streets either do not perceive the audibile or visible alarms indicating the impending approach of the emergency vehicle or do not believe that the approach is sufficiently imminent and that they need to take evasive action. In some cases they will proceed through the intersection in the path of an emergency vehicle causing accidents which not only are serious enough to cause loss of life but prevent the emergency vehicles from reaching their destination. Additionally since today's highways, and city streets are becoming increasingly congested with automobile, truck, bus and pedestrian traffic, difficulty in the movement of emergency vehicles through crowded intersections is increasing. Therefore it would be an advantage if an emergency vehicle could approach an intersection with knowledge that it can safely proceed through the intersection at the greatest possible speed without danger of accident or injury. p Other systems have been proposed some few of which have been commercially successful to provide warnings at intersections. For one reason or another either because they were inadequate, complex or for other reasons these systems have not received widespread acceptance. One such system is typified for example, in U.S. Pat. No. 3,550,078, reissue 28,100, reissued Aug. 6, 1974 to W. H. Long entitled Traffic Signal Remote Control System. The invention described in this patent provides the ability of an emergency vehicle to remotely control traffic light signals so as to provide, for example, a green light for the approaching direction of an emergency vehicle and a red light for cross traffic. However, the system of the Long patent does not alert or forewarn vehicles and pedestrians approaching the intersection or in the vicinity of intersection that an emergency vehicle's approach is imminent. That device creates a dangerous situation by allowing traffic to flow at the intersection in advance of a non-forewarned approach of an emergency vehicle. For example, while the system of this patent allows the traffic signals to be changed by the approaching vehicle, traffic along the path of the emergency vehicle can still proceed. If the operators or pedestrians are inattentive, have impaired hearing or do not hear or see any signals they can impede the progress of the emergency vehicle or even cause an accident.
It is therefore one object of the present invention to provide means by which the emergency vehicles may safely move with deliberate speed through street and highway intersections with relative safety.
Another object of the present invention is to provide a system for automatic remote pre-emption of control of traffic signals at selected intersections.
An additional object of the present invention is to provide a system by means of which operators of emergency vehicles can remotely communicate with traffic control systems which will provide the identity and direction of approach of an emergency vehicle to indicate to traffic at the intersection the direction from which the vehicle is approaching as well as the direction from which it may be departing the intersection.
Still an additional object of the present invention is to pre-empt the control of traffic signals at an intersection to change to a desired emergency signal condition in addition to providing early warning information at the intersection to vehicles and pedestrians forewarning them of the impending approach and egress of emergency vehicles.
Yet a further object of the present invention is to provide means for pre-emptive automatic control of traffic signals to halt the normal flow of all traffic through an intersection so that an emergency vehicle can speedily and safely pass through the intersection.
Still a further object of the present invention is to provide an extremely reliable and relatively inexpensive apparatus that can be installed and adapted to existing intersections with a minimum addition of electrical interconnections or mounting structures to those already present at the intersection, and which can be used in combination with existing traffic control systems to remotely control the operation of traffic light signals.