Patent Publication Number: US-6700504-B1

Title: Method and system for safe emergency vehicle operation using route calculation

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to emergency vehicles, such as ambulances, fire engines, police cars, and so on, and more particularly the present invention relates to a system that helps make the operation of emergency vehicles safer. 
     Emergency vehicles, such as ambulances, fire engines, police cars, and so on, can pose hazards to other vehicles on the roads. While traveling to and from scenes of emergencies, emergency vehicles have been involved in accidents with other vehicles or have caused other vehicles to have accidents. There have been prior attempts to make the operation of emergency vehicles while traveling to and from scenes of emergencies safer. For example, U.S. Pat. No. 5,539,398 describes a system wherein an emergency vehicle is equipped with a GPS receiver. Equipment in the emergency vehicle uses the GPS receiver to determine the emergency vehicle&#39;s location and heading. Data indicating the emergency vehicle&#39;s location and heading are transmitted from the emergency vehicle to intersection controllers that are located at each intersection that has traffic signals. The intersection controller uses the data indicating the emergency vehicle position and heading to determine whether the emergency vehicle is on any road that might lead to the intersection. If the emergency vehicle is on any road heading toward an intersection, the intersection controller operates the traffic signals at the intersection to give the emergency vehicle the right-of-way. 
     Although the system described in U.S. Pat. No. 5,539 may address some safety issues concerning the operation of emergency vehicles, there is still room for improvement. For example, there is a need to predict the path of an emergency vehicle better so that safety measures may be implemented along the path. 
     SUMMARY OF THE INVENTION 
     To address these and other objectives, the present invention comprises a system and method that help make operation of emergency vehicles safer. When an emergency vehicle is traveling to or from an emergency, a route for the emergency vehicle to travel is calculated using a navigation system. Traffic signals along the calculated route are controlled to give the emergency vehicle the right-of-way along the calculated route. In addition, data indicating the calculated route of the emergency vehicle are transmitted to other vehicles located along the calculated route. In each of these other vehicles, warnings are provided to the vehicle drivers. These warnings indicate the presence of the emergency vehicle and optionally the expected path of travel of the emergency vehicle. 
     According to one aspect of the invention, a route for the emergency vehicle is calculated at a central location. Data representing the route are sent from the central location to the emergency vehicle where driving instructions are provided to the emergency vehicle driver for following the route. Data are also sent from the central location to the other vehicles along the route so that warnings can be provided to drivers of these other vehicles. The central database location also sends data to traffic signal controllers to provide the emergency vehicle with the right-of-way along the calculated route. 
     According to an alternative aspect of the invention, a route for the emergency vehicle is calculated using a navigation system in the emergency vehicle. The navigation system in the emergency vehicle provides driving instructions to the emergency vehicle driver for following the route. Data are also sent from the navigation system in the emergency vehicle to other vehicles within proximity to the emergency vehicle so that warnings can be provided to drivers of these other vehicles. The navigation system in the emergency vehicle also sends data to traffic signal controllers to provide the emergency vehicle with the right-of-way along the calculated route. 
     According to another aspect of the invention, data representing the traveling status (e.g., current location, heading, speed, acceleration, turn signal status, and optionally the route) of the emergency vehicle and the other vehicles located around the emergency vehicle are shared so that each vehicle (including the emergency vehicle) is informed of the traveling status of the vehicles around it. Using this information, vehicle paths and trajectories are predicted in order to identify the probability of potential accident occurrences. Warnings are provided, as appropriate, to avoid occurrences of accidents. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an illustration that shows an emergency vehicle and other vehicles located on a road network in a geographic area. 
     FIG. 2 is a block diagram showing components of an emergency vehicle warning system including an emergency vehicle dispatcher system, an emergency vehicle system, a traffic signal controller system, and an end-user vehicle warning system. 
     FIG. 3 is a flow chart showing steps performed by the emergency vehicle warning system in FIG.  2 . 
     FIG. 4 is an illustration of a dashboard in one of the other vehicles in FIG.  1  and shows a portion of the operation of the emergency vehicle warning system according to the embodiment described in FIGS. 2 and 3. 
     FIG. 5 is an illustration of a navigation system in one of the other vehicles in FIG.  1  and shows a portion of the operation of the emergency vehicle warning system according to the embodiment described in FIGS. 2 and 3. 
     FIG. 6 is a block diagram showing components of another embodiment of the emergency vehicle warning system. 
     FIG. 7 is a flow chart of an alternative embodiment that includes a path prediction program. 
    
    
     DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
     I. FIRST EMBODIMENT 
     A. Overview 
     A first embodiment of an emergency vehicle safety system is described with reference to FIGS. 1-5. According to this embodiment, a route for the emergency vehicle is calculated at a central location and data representing the route are sent from the central location to the emergency vehicle. 
     FIG. 1 shows a portion  10  of a geographic area  12 . Located in the geographic area  12  is a road network  14 . The road network  14  is comprised of roads and intersections. In FIG. 1, a road segment  16  forms that portion of a road between intersections  18  with other roads. 
     Traffic control signals  20  (e.g., stop lights) are associated with some of the intersections  18  in FIG.  1 . 
     Located on the road network  14  in FIG. 1 is an emergency vehicle  22 . The emergency vehicle  22  is an ambulance, although alternatively, the emergency vehicle could be a police car, a fire engine, a tow truck, or any other type of emergency vehicle. The emergency vehicle  22  is traveling toward a destination  24 , which is located along one of the road segments  16  in the geographic area  12 . 
     Also located on the road network  14  are other vehicles  26 ( 1 ),  26 ( 2 ) . . . . The other vehicles  26  include privately owned vehicles, but may also include commercial vehicles (e.g., trucks), publicly owned vehicles (e.g., busses), or even other emergency vehicles, including other emergency vehicles heading toward the same emergency. 
     The geographic area  12  is served by an emergency vehicle safety system. FIG. 2 shows components of a first embodiment of the emergency vehicle safety system  28 . The emergency vehicle safety system  28  in FIG. 2 includes four component sub-systems. These component sub-systems include an emergency vehicle dispatcher system  30 , an emergency vehicle system  32 , an end-user vehicle warning system  34 , and a traffic signal controller system  36 . 
     B. The Emergency Vehicle Dispatcher System 
     Referring first to the emergency vehicle dispatcher system  30 , the emergency vehicle dispatcher system  30  includes a base unit navigation system  40 . The base unit navigation system  40  is a combination of hardware and software components. The hardware components in the base unit navigation system  40  may include one or more processors, memory, data storage, a user interface, and so on. 
     The base unit navigation system  40  uses geographic data. The geographic data used by the base unit navigation system  40  may be organized into one or more geographic databases  46 . The data in the geographic database  46  include information about the geographic area ( 12  in FIG.  1 ), and in particular, the geographic database  46  includes data about the roads and intersections that form the road network ( 14  in FIG. 1) located in the geographic area  12 . The kinds of data about roads and intersections include the locations of the roads and intersections, the speed limits (or ranges), address ranges, locations of traffic signals, number of lanes, lane width, names of roads, functional classes of roads, turn restrictions at intersections, and so on. 
     The software components of the base unit navigation system  40  include one or more applications  50 . In the embodiment of FIG. 2, the applications  50  include a route calculation application  50 ( 1 ), a vehicle tracking application  50 ( 2 ) and a notification application  50 ( 3 ). The emergency vehicle dispatcher system  30  may also include other applications. In one embodiment, the navigation applications  50  are written in the C programming language although in alternative embodiments other programming languages may be used, such as C++, Java, Visual Basic, and so on. 
     The route calculation application  50 ( 1 ) determines a route for the emergency vehicle  22  to travel along the road network ( 14  in FIG. 1) to reach a desired destination. In order to calculate a route, the route calculation application  50 ( 1 ) is provided with data identifying a starting location (origin) and a desired destination location. In this embodiment, the destination location may be the scene of the emergency and the starting location may be the location from which the emergency vehicle  22  starts its trip to the scene of the emergency. Alternatively, the destination location may be an emergency treatment facility, e.g., a hospital, and the starting location may be the location from which the emergency vehicle  22  starts its trip to the treatment facility, e.g., the scene of the emergency. The data used to identify these locations may include the geographic coordinates of these locations, the street addresses of these locations, the names of these locations (e.g., General Hospital) or specification of the data entities in the geographic database  46  that represent the road segments upon which these locations are located. 
     Given at least the identification of a starting location (origin) and a desired destination location, the route calculation application  50 ( 1 ) determines one or more solution routes between the starting location and the destination location. A solution route is formed of a series of connected road segments over which the emergency vehicle can travel from the starting location to the destination location. When the route calculation application  50 ( 1 ) calculates a route, it accesses the geographic database  46  and obtains data that represent road segments around and between the starting location and the destination location. The road calculation application  50 ( 1 ) uses the data to determine at least one valid solution route from the starting location to the destination location. The route calculation application  50 ( 1 ) may attempt to find a solution route that takes the least time to travel. 
     The route calculation application  50 ( 1 ) may use various means or algorithms in determining solution routes. Methods for route calculation are disclosed in Ser. No. 09/047,698, filed Mar. 25, 1998, the entire disclosure of which is incorporated by reference herein. (The methods disclosed in the aforementioned patent application represent only some of the ways that routes can be calculated and the subject matter claimed herein is not limited to any particular method of route calculation. Any suitable route calculation method now known or developed in the future may be employed.) 
     The route calculation application  50 ( 1 ) provides an output in the form of an ordered list identifying a plurality of road segments that form the continuous navigable route between the origin and the destination. 
     As stated above, the vehicle tracking application  50 ( 2 ) is another of the software applications  50  in the base unit navigation system  40 . The vehicle tracking application  50 ( 2 ) keeps track of the positions of the other vehicles  26 ( 1 ),  26 ( 2 ),  26 ( 3 ) . . . that are traveling on the road network  14 . There are several different technologies that the vehicle tracking application  50 ( 2 ) can use to keep track of the positions of the other vehicles  26 . According to one alternative, each of the other vehicles  26  includes positioning system hardware, such as a GPS system, inertial sensors, etc., by which the position of the associated vehicle can be determined. Each of the vehicles equipped in this manner transmits data indicating its position to the emergency vehicle dispatcher system  20 . Optionally, each of these vehicles also transmits data about its traveling status including such information as heading, speed, acceleration, turn signal status, etc. These data are transmitted by the other vehicles  26  on a regular basis. The transmission of vehicle position data from the vehicles  26  may be used for purposes in addition to emergency vehicle notification. As an example, the transmission of vehicle position data from the vehicles  26  may be part of a system that provides traffic and route guidance information to the other vehicles  26 . 
     As stated above, there are other ways to determine the positions of the other vehicles  26 . For example, the positions of the other vehicles  26  can be determined by using a cellular phone location determining system. (A “cellular phone” is understood to include any wireless telephone technology, including PCS, etc.) The positions of cellular phones can be determined using location determining systems that are part of the cellular phone network. These location determining systems are used to locate cellular phone users who request emergency assistance. By using a cellular phone location determining system, the cellular phones that are located in automobiles can be used to determine the locations of the automobiles. This information is provided to the emergency vehicle dispatcher system  30  where it is used by the vehicle tracking application  50 ( 2 ) to keep track of the vehicles  26  in the geographic area  12 . (According to an alternative, some cellular phones are also equipped with a GPS chip allowing for either GPS or cellular location technology.) 
     The emergency vehicle dispatcher system  30  may keep track of all the other vehicles  26  on the road network  14  or alternatively, the emergency vehicle dispatcher system  30  may keep track of only some of the other vehicles  26  on the road network  14 . 
     As further stated above, the notification application  50 ( 3 ) is included among the software applications  50  in the base unit navigation system  40 . The notification application  50 ( 3 ) receives data from the route calculation application  50 ( 1 ) that indicates the route calculated for the emergency vehicle  22 . The notification application  50 ( 3 ) also receives data indicating the positions of the other vehicles  26  from the vehicle tracking application  50 ( 2 ). The notification application  50 ( 3 ) provides an output to the traffic control devices  20 . The traffic control devices  20  use the output from the notification application  50 ( 3 ) to provide the emergency vehicle  22  with the right-of-way along the calculated route, as explained in more detail below. The notification application  50 ( 3 ) also provides an output to each of the other vehicles  26  that is located close to the calculated route of the emergency vehicle  22 , as explained in more detail below. 
     The emergency vehicle dispatcher system  30  includes an input interface  60 . The input interface  60  provides for receiving data that indicates the type of emergency vehicle to send and data indicating the origin and destination for the emergency vehicle. The input interface  60  may receive these data automatically from an emergency call handling system, e.g., a “911-type system.” Alternatively, the input interface  60  may provide for receiving these inputs from a human operator, e.g., via a keyboard, etc. After receiving data that indicate the type of emergency vehicle to send and data indicating the origin and destination for the emergency vehicle, the input interface  60  provides these data to the base unit navigation system  40 . 
     The emergency vehicle dispatcher system  30  includes a communications system  62 . The communications system  62  includes appropriate equipment (including hardware and software) for exchanging data wirelessly with the emergency vehicle system  32  and each end-user vehicle warning system  34 . The communications system  62  uses any suitable technology for sending and receiving data wirelessly in a geographic area, including cellular, PCS, etc. The communications system  62  also includes appropriate equipment for sending data or signals to each traffic signal controller system  36 . The communications system  62  is operatively coupled to the base unit navigation system  40 . The communications system  62  receives data from the base unit navigation system  40  that indicates the route calculated for the emergency vehicle  22  and sends these data to the emergency vehicle system  32 . The communications system  62  also sends the data indicating the emergency vehicle route to each end-user vehicle warning system  34 . The communications system  62  also sends data to each traffic signal controller system  36  to operate the stoplights  20 . 
     C. The Emergency Vehicle System 
     FIG. 2 shows components of the emergency vehicle system  32 . The emergency vehicle system  32  is located in the emergency vehicle ( 22  in FIG.  1 ). The emergency vehicle system  32  includes a communications system  70  and a remote unit navigation system  76 . The communications system  70  in the emergency vehicle system  32  is compatible with the communications system  62  in the emergency vehicle dispatcher system  30  in order to exchange data wirelessly therewith. 
     The remote unit navigation system  76  in the emergency vehicle system  32  is a counterpart of the base unit navigation system  40  in the emergency vehicle dispatcher system  30 . These two systems work together as part of the emergency vehicle safety system  28 . 
     The remote unit navigation system  76  in the emergency vehicle system  32  is a combination of hardware and software components. The hardware components of the remote unit navigation system  76  may include one or more processors, memory, data storage, and so on. The remote unit navigation system  76  also includes a positioning system  80  that determines the position of the emergency vehicle  22  in which it is installed. The positioning system  80  may include sensors  84  or other components that sense the speed, orientation, direction, and so on, of the emergency vehicle  22 . The positioning system  80  may also include a GPS system. 
     The remote unit navigation system  76  also includes a user interface  90 . The user interface  90  includes appropriate means  92  for receiving input from an operator in the emergency vehicle  22 . These inputting means  92  may include a keyboard, keypad, or other type of input panel, a microphone, as well as other means for accepting operator input, such as voice recognition software, and so on. The user interface  90  also includes appropriate means  96  for providing information back to the operator in the emergency vehicle  22 . The information providing means  96  may include a display and a speaker (including speech synthesis hardware and software) through which the operator in the emergency vehicle can be provided with information from the remote unit navigation system  76 . 
     The software components of the remote unit navigation system  76  include one or more applications  98 . In the embodiment of FIG. 2, the applications  98  include a route guidance application  98 ( 1 ), a vehicle positioning application  98 ( 2 ), and optionally, a map display application  98 ( 3 ). The navigation programming  98  in the remote unit navigation system  76  may include other applications in addition to these. 
     The route guidance application  98 ( 1 ) receives data indicating a route to a destination and then uses the data to develop driving instructions for following the route. In the embodiment of FIG. 2, the data indicating a route are developed by the route calculation application  50 ( 1 ) in the emergency vehicle dispatcher system  30 . The route guidance application  98 ( 1 ) uses the data to provide instructions and advice to the emergency vehicle driver to travel the route determined by the route calculation application  50 ( 1 ). The route guidance application  98 ( 1 ) may include functions that identify locations along the calculated route at which maneuvering instructions may be provided to the emergency vehicle driver. The route guidance application  98 ( 1 ) may also include functions that formulate the maneuvering instructions for visual output and/or audio output. The route guidance application  98 ( 1 ) may provide the maneuvering instructions all at once, or alternatively, the route guidance application  98 ( 1 ) may provide the maneuvering instructions one at a time as the emergency vehicle  22  is traveling. In one embodiment, each maneuvering instruction is provided separately (or in small groups of combined maneuvering instructions) in advance of when the specific maneuver is required to be taken so that the emergency vehicle driver can prepare to make the required maneuver. 
     The vehicle positioning application  98 ( 2 ) determines the position of the emergency vehicle  22  relative to the road network. The vehicle positioning application  98 ( 2 ) uses the output from the positioning system  80  and data indicating the positions of roads to determine on which road segment the emergency vehicle  22  is located and its direction of travel. The vehicle positioning application  98 ( 2 ) may obtain data indicating the positions of roads from a copy of the geographic database  99  stored locally in the emergency vehicle system  32 , or alternatively, the vehicle positioning application  98 ( 2 ) may receive data indicating the positions of roads from the emergency vehicle dispatcher system  30 . 
     Using the data indicating the position of the emergency vehicle  22  relative to the roads, the route guidance application  98 ( 1 ) can provide maneuvering instructions at appropriate times and/or locations as the emergency vehicle travels along the calculated route. For example, the maneuver instructions can be provided as the emergency vehicle approaches positions at which maneuvers are required. 
     The vehicle positioning application  98 ( 2 ) can also be used to determine whether the emergency vehicle  22  has departed from the calculated route. 
     The map display application  98 ( 3 ) is an optional application within the remote unit navigation system  76 . The map display application  98 ( 3 ) is used to show a graphical map of the area around the emergency vehicle to the emergency vehicle operator. The graphical map is shown on the display screen that is included among the output devices  96  of the user interface  90 . The data used by the map display application  98 ( 3 ) to generate the map may be obtained from the on-board geographic database  99 , if available, or may be obtained from the emergency vehicle dispatcher system  30 . The map display application  98 ( 3 ) may highlight the route for the emergency vehicle to travel on the displayed map. 
     The communications system  70  in the emergency vehicle system  32  exchanges data with the counterpart communications system  62  in the emergency vehicle dispatcher system  30 . The communications system  70  in the emergency vehicle system  32  is operatively coupled to the remote unit navigation system  76 . When data indicating the calculated route for the emergency vehicle to follow are received from the emergency vehicle dispatcher system  30  via the communication system  70 , these data are forwarded to the remote unit navigation system  76 . 
     As the emergency vehicle travels along its route, the remote unit navigation system  76  in the emergency vehicle continuously collects data regarding the emergency vehicle traveling status. The emergency vehicle traveling status data include at least the current location of the emergency vehicle (determined using the vehicle positioning application  98 ( 2 )), and preferably also include other data that indicate the heading, speed, acceleration, and turn signal status of the emergency vehicle. The emergency vehicle traveling status data may also include other information. The emergency vehicle traveling status data are sent via the communications system  70  to the emergency vehicle dispatcher system  30 . 
     D. The Warning Systems in the End Users&#39; Vehicles 
     FIG. 2 shows components of one of the end-user vehicle warning systems  34 . The end-user vehicle warning system  34  is located in one of the end users&#39; vehicles ( 26  in FIG.  1 ). The end-user vehicle warning system  34  allows the end user&#39;s vehicle  26  to receive data from the emergency vehicle dispatcher system  30  that indicate the path that the emergency vehicle is expected to follow. The end-user vehicle warning system  34  may also receive data from the emergency vehicle dispatcher system  30  that indicate other aspects of the emergency vehicle traveling status, such as the current location, the heading, speed, acceleration, and turning signal status of the emergency vehicle. The end-user vehicle warning system  34  includes a communications system  102 , a user interface  104 , and optionally a positioning system  108 . The communications system  102  in the end-user vehicle warning system  34  is compatible with the communications system  62  in the emergency vehicle dispatcher system  30  in order to receive data wirelessly therefrom. 
     The user interface  104  in the end-user vehicle warning system  34  includes a means for providing information to the driver (i.e., the end user) in the vehicle  26 . The information providing means may include a speaker and optionally a display through which the end user in the vehicle  26  can be provided with information about the presence of the emergency vehicle in the vicinity of the end user&#39;s vehicle  26  and the expected path of travel of the emergency vehicle. 
     As stated above, the end-user vehicle warning system  34  may include a positioning system  108 . The positioning system  108  is optional. If the end-user vehicle warning system  34  has a positioning system  108 , it may be similar or identical to the positioning system  80  that is part of the remote unit navigation system  76  located in the emergency vehicle. The end-user positioning system  108  may include sensors or other components that sense the speed, orientation, direction, and so on, of the end user&#39;s vehicle  26 . The positioning system  108  may also include a GPS system. The positioning system  108  also includes appropriate software to determine the position of the end user&#39;s vehicle  26 . The position determined by the end user&#39;s positioning system may be an absolute position (e.g., latitude and longitude coordinates) or may be a position relative to the road network. The end user&#39;s positioning system  108  may use a geographic database for this purpose. 
     If the end user&#39;s vehicle  26  includes a navigation system, the positioning system and user interface of the navigation system may be used as the positioning system and user interface for the end-user vehicle warning system  34 . According to this alternative, the functions of the end-user vehicle warning system  34  may be provided as a feature of the navigation system in the end user&#39;s vehicle. 
     E. The Traffic Signal Controller System 
     FIG. 2 shows components of one of the traffic signal controller systems  36 . The traffic signal controller system  36  is associated with one (or more) of the traffic signals ( 20  in FIG.  1 ). The traffic signal controller system  36  receives the data from the emergency vehicle dispatcher system  30  that indicate the desired operation of the associated traffic signal  20 . In general, the data from the emergency vehicle dispatcher system  30  will cause the traffic signals located along the route calculated for the emergency vehicle to operate to give the emergency vehicle the right-of-way. The traffic signal controller system  36  includes a communications system  120 . The communications system  120  is compatible with the communications system  62  in the emergency vehicle dispatcher system  30  in order to receive data or signals therefrom. The communications system  120  may be wireless or may be connected to a land-based communications system in order to receive data from the emergency vehicle dispatcher system  30 . 
     The traffic signal controller system  36  is operatively coupled to one or more traffic signals  20 . The data received by the traffic signal controller system  36  from the emergency vehicle dispatcher system  30  are used to control operation of the one or more traffic signals  20  associated therewith. 
     F. Operation 
     FIG. 3 is a flow chart that shows operation of the emergency vehicle safety system  28 . The operation of the emergency vehicle safety system  28  includes processes performed by the emergency vehicle dispatcher system  30 , the traffic signal controller systems  34 , the end-user warning systems  34  and the emergency vehicle system  32 . 
     Operation of the emergency vehicle safety system  28  begins with the process in the emergency vehicle dispatcher system  30 . The emergency vehicle dispatcher system  30  receives data indicating an origin and destination for the emergency vehicle (Step  200 ). These data are received by the input interface  60  of the emergency vehicle dispatcher system  30 . These data are provided to the base unit navigation system  40 . The route calculation application  50 ( 1 ) in the base unit navigation system  40  uses these data to determine a route for the emergency vehicle to follow to reach the destination (Step  204 ). The route calculation application  50 ( 1 ) provides data indicating the route to the emergency vehicle  22 . In addition, the route calculation application  50 ( 1 ) provides data indicating the route of the emergency vehicle to the notification application  50 ( 3 ) in the base unit navigation system  40 . The notification application  50 ( 3 ) identifies all the controllable traffic signals located along the route calculated for the emergency vehicle (Step  206 ). The notification application  50 ( 3 ) also determines the expected time of arrival of the emergency vehicle at each of the controllable traffic signals located along the calculated route. Based upon this information, the notification application  50 ( 3 ) sends data to each of the traffic signal controller systems  34  associated with the controllable traffic signals located along the calculated route. The data indicate the type of operation for the associated traffic signal to perform as well as the time at which the operation for the associated traffic signal is to take place in order to give the emergency vehicle a right-of-way along the calculated route (Step  208 ). 
     Each of the traffic signal controller systems  34  located along the calculated route receives the data from the notification application  50 ( 3 ) in the emergency vehicle dispatcher system  30  (Step  212 ). Using these data, each of the traffic signal controller systems  34  operates the one or more traffic signals  20  associated therewith to provide the emergency vehicle with the right-of-way (Step  216 ). 
     Referring back to the process in the emergency vehicle dispatcher system  30 , the vehicle tracking application  50 ( 2 ) in the emergency vehicle dispatcher system  30  determines the end users&#39; vehicles  26  that are located along the calculated route of the emergency vehicle (Step  220 ). The vehicle tracking application  50 ( 2 ) performs this function by continuously obtaining data indicating the positions of end users&#39; vehicles  26  as they travel along the road network  14  in the geographic area. Alternatively, the vehicle tracking application  50 ( 2 ) can perform this function while calculating a route for the emergency vehicle by sending a message to each of the end users&#39; vehicles  26  requesting that they send back data indicating their positions along the road network  14  in the geographic area. 
     After determining which of the end users&#39; vehicles are located along the calculated route of the emergency vehicle, the notification application  50 ( 3 ) sends data to these end users&#39; vehicles that indicate the path that the emergency vehicle is expected to take (Step  224 ). The data may include data indicating the entire route of the emergency vehicle or alternatively, the data may include only the data relating to that portion of the route of the emergency vehicle close to each end user&#39;s vehicle. 
     Each end-user vehicle warning system  34  receives the data from the emergency vehicle dispatcher system  30  (Step  228 ). The end-user vehicle warning system  34  uses the data to provide a warning to the end user (Step  232 ). The warning is provided to the end user using the user interface ( 104  in FIG. 2) of the end-user vehicle warning system  34 . 
     FIG. 4 illustrates one way that the end user can be provided with a warning by the end-user vehicle warning system  34 . FIG. 4 shows a dashboard  240  in one of the end users&#39; vehicles  26 . Located in the dashboard is the user interface  104  of the end-user vehicle warning system  34 . In this embodiment, the user interface  104  is part of a vehicle navigation system  244  installed in the end user&#39;s vehicle  26 . The user interface  104  includes a speaker  248 . Upon receiving data from the emergency vehicle dispatcher system  30  that indicates the path of the emergency vehicle, the end-user vehicle warning system  34  provides an audible warning using the speaker  248 . The wording of the warning may be determined by software in either the emergency vehicle dispatcher system  30  or the end-user vehicle warning system  34 . 
     FIG. 5 illustrates another way that the end user can be provided with a warning by the end-user vehicle warning system  34 . FIG. 5 shows a display screen  250 . The display screen  250  is part of the user interface  104  of the end-user vehicle warning system  34  in the end user&#39;s vehicle  26 . The display screen  250  may be part of an in-vehicle navigation system  256  located in the end user&#39;s vehicle. Upon receiving data from the emergency vehicle dispatcher system  30  that indicates the path of the emergency vehicle, the end-user vehicle warning system  34  provides a visual warning using the display screen  250 . The visual warning may include text, graphics, a map or any combination of text, graphics or a map. The visual warning may be determined by software in either the emergency vehicle dispatcher system  30 , the end-user vehicle warning system  34 , or the in-vehicle navigation system  256 . In the embodiment of FIG. 5, the end user is provided with a clear indication of the path of the emergency vehicle. 
     Referring again to FIG. 3, it was stated that when the route calculation application  50 ( 1 ) in the emergency vehicle dispatcher system  30  calculates a route for the emergency vehicle to follow, it sends data indicating the route to the emergency vehicle system  32 . In the emergency vehicle  22 , the route guidance application  98 ( 1 ) in the remote unit navigation system  76  of the emergency vehicle system  32  uses the data from the emergency vehicle dispatcher system  20  to provide the operator of the emergency vehicle with driving instructions for following the calculated route to reach the destination. While the emergency vehicle is traveling along the route to the destination, the vehicle positioning application  98 ( 2 ) in the remote unit navigation system  76  determines the position of the emergency vehicle relative to the calculated route in order to provide maneuvering instructions at appropriate times and locations. 
     If the vehicle positioning application  98 ( 2 ) determines that the emergency vehicle has reached the destination, the operation of the emergency warning safety system  28  ends (Steps  264  and  266 ). However, if at Step  264  the vehicle positioning application  98 ( 2 ) determines that the emergency vehicle is still on its way to the destination, the operation of the emergency warning safety system  28  continues. The vehicle positioning application  98 ( 2 ) in the emergency vehicle next determines whether the emergency vehicle has departed from the calculated route (Step  270 ). If the emergency vehicle has not departed from the calculated route, the operation of the emergency warning system continues by looping back to the step (Step  220 ) in the process performed by the emergency vehicle dispatcher system  20  in which the other vehicles located along the path of the emergency vehicle are determined. This step (i.e., Step  220 ), and the steps that follow it, are repeated because it is possible that some of the other vehicles  26  that were not identified as being along the path of the emergency vehicle initially (and therefore not notified initially) may travel into the path of the emergency vehicle at a later time. Also, it is possible that some other vehicles  26  were not being operated (e.g., were not turned on) when the initial notification about the emergency vehicle was sent, and therefore were not notified. Accordingly, if the emergency vehicle has not yet reached its destination (as determined at Step  264 ) and has not departed from its calculated route (as determined at Step  270 ), the process in the emergency vehicle dispatcher system  20  is repeated starting with the step in which the other vehicles along the path of the calculated route of the emergency vehicle are identified (Step  220 ). 
     The emergency vehicle may depart from traveling along the calculated route for a number of reasons. For example, the emergency vehicle driver may determine that a different route is better. Alternatively, the calculated route may be blocked. According to still another possibility, the emergency vehicle driver may mistakenly take a wrong turn. Regardless of the reason, the vehicle positioning application  98 ( 2 ) in the emergency vehicle will determine when the emergency vehicle has departed from the calculated route (Step  270 ). If the emergency vehicle has departed from the calculated route, a new calculated route is needed. Accordingly, if the vehicle positioning application  98 ( 2 ) in the emergency vehicle determines that the emergency vehicle has departed from the calculated route (at Step  270 ), the process loops back to the step (i.e., Step  200 ) in the process performed by the emergency vehicle dispatcher system  20  in which the base system navigation unit  40  receives inputs indicating the origin and destination. When the emergency vehicle has departed from the calculated route, the current position of the emergency vehicle is used as the new origin. The destination remains the same. Then, the process performed by the emergency vehicle dispatcher system  20  continues. Because a new route is calculated, the steps of determining the traffic signals along the new route (Step  206 ), providing the right-of-way along the new route (Step  208 ), determining the other vehicles along the new route (Step  220 ) and notifying the other vehicles along the new route (Step  206 ) are all performed again. 
     An advantage associated with having the emergency vehicle dispatching performed from a centralized location is that it facilitates coordinating multiple emergency vehicles moving across a city. Another advantage associated with having the emergency vehicle dispatching performed from a centralized location is that it enables more robust security to be implemented. 
     II. ALTERNATIVE EMBODIMENTS 
     A. First Alternative Embodiment 
     In the embodiment described above, the route for the emergency vehicle to travel is calculated on the emergency vehicle dispatcher system and transmitted to the emergency vehicle. In this first alternative embodiment, the route for the emergency vehicle to travel is calculated by the emergency vehicle system located in the emergency vehicle. Then, data are transmitted from the emergency vehicle system to warning systems located in the other vehicles. In one embodiment, the data are transmitted using a low-powered inter-vehicle communications system. Such systems provide for the exchange of data between vehicles located relatively close together, e.g., within 1 km. In addition, the low-powered communications system can be used to transmit data from the emergency vehicle system to the traffic signal controller systems. 
     FIG. 6 is a block diagram showing components of this embodiment  328 . Some of the components in FIG. 6 are similar or identical to those described in connection with FIG.  2  and like components are labeled with the same numbers. In FIG. 6, an emergency vehicle system  332  includes a remote unit navigation system  376 . The remote unit navigation system  376  is similar to the remote unit navigation system  76  described in connection with the first embodiment. In addition to the functions performed by the remote unit navigation system  76  described in connection with the first embodiment, the remote unit navigation system  376  also performs some of the functions of the emergency vehicle dispatcher system  20  in the first embodiment. 
     The remote unit navigation system  376  receives input indicating an origin and destination for a route for the emergency vehicle to travel. As in the first embodiment, the destination may be the scene of an emergency or alternatively, the destination may be an emergency treatment facility. The origin may be the current location of the emergency vehicle as determined by the vehicle positioning application  98 ( 2 ) in the remote unit navigation system  376  in the emergency vehicle. 
     The input indicating the destination may be made manually by an operator in the emergency vehicle. The operator may use the user interface  90  of the emergency vehicle system  332  for this purpose. Alternatively, the input indicating the destination may be received over a wireless communications system from another service, such as a service that handles emergency calls. 
     Upon receiving inputs indicating an origin and destination, a route calculation application  350 ( 1 ) located in the remote unit navigation system  376  calculates a route between the origin and destination. The route calculation application  350 ( 1 ) is similar or identical to the route calculation application  50 ( 1 ) located in the base unit navigation system  40  in the emergency vehicle dispatcher system  30 , described above. 
     After the route calculation application  350 ( 1 ) determines a route between the origin and destination, the data indicating the route are used to provide route guidance to the emergency vehicle driver in order to follow the route. In addition, a notification application  350 ( 3 ) in the remote unit navigation system  376  transmits data indicating the route to the end-user vehicle warning systems  34 . The data are transmitted via the communication system  370  in the emergency vehicle system  332 . The communications system  370  in the emergency vehicle system  332  is similar to the communications system  70  in the emergency vehicle system  32  in the first embodiment with the exception that it includes the capability of the emergency vehicle dispatcher system  30  of transmitting data to the end-user vehicle warning systems  34 , or at least those end-user vehicle warning systems  34  located close to the emergency vehicle  22  or along the path of the emergency vehicle. 
     The data indicating the emergency vehicle route that are sent from the emergency vehicle system  332  to each of the end users&#39; vehicle warning systems are used in each end-user vehicle warning system  34  to provide a warning to the driver in the vehicle  26  about the presence of the emergency vehicle and the expected route of the emergency vehicle. The warning may be similar or identical to the warnings described above in connection with the first embodiment. In this embodiment, each end-user vehicle warning system  34  may receive data indicating the entire route of the emergency vehicle, determine whether the associated vehicle is close to the expected route of the emergency vehicle and then provide an appropriate warning to the end user/driver of the vehicle. Alternatively, the remote unit navigation system  376  in the emergency vehicle system  332  may perform a vehicle tracking function, similar to the function performed by the vehicle tracking application  50 ( 2 ) in the first embodiment, and transmit data about the emergency vehicle route (or portion thereof) to only those other vehicles located along the expected path of the emergency vehicle. 
     The notification application  350 ( 3 ) in the remote unit navigation system  376  also transmits data to the traffic signal controller systems  36 . These data are used by the traffic signal controller systems  36  to operate the traffic signals along the calculated route to give the emergency vehicle the right-of-way. 
     B. Path Prediction Program Embodiment 
     In another alternative embodiment, the emergency vehicle warning systems in the end users&#39; vehicles and the system in the emergency vehicle include path prediction programs. These path prediction programs use traveling status data which are exchanged between the emergency vehicle and the other vehicles. As mentioned above, the emergency vehicle is equipped to collect traveling status data. The traveling status data of the emergency vehicle may include (but are not necessarily limited to) the current location, heading, speed, acceleration, turn signal status, and route of the emergency vehicle. Each of the other vehicles located in the area of the emergency vehicle may also be equipped to collect its associated traveling status data. The traveling status data of the emergency vehicle are transmitted to the other vehicles located close to the emergency vehicle. Similarly, the traveling status data of each other vehicle are also transmitted to the emergency vehicle (as well as the other vehicles located close by). Using the traveling status data from the emergency vehicle, the path prediction program in each warning system in each of the other vehicles predicts the path of the emergency vehicle. The path prediction program compares the predicted path of the emergency vehicle with the predicted path of the vehicle in which the warning system is installed. Based on this comparison, a probability of an accident between the emergency vehicle and the vehicle in which the warning system is installed is calculated. If a significant probability of an accident exists, the path prediction program in the end user&#39;s vehicle (and the navigation system in the emergency vehicle) provides a warning. The path prediction program may indicate a recommended action to the end user vehicle driver (e.g., pull over, stop, and so on). The path prediction program may also recommend an action to the emergency vehicle driver. 
     FIG. 7 is a flow chart that shows the steps performed by the notification program in the emergency vehicle and the path prediction program in one of the end user&#39;s vehicles. In FIG. 7, a notification program  400  in the emergency vehicle system  402  collects traveling status data (Step  404 ). The traveling status data include the current location, heading, speed, acceleration, turn signal status, and route of the emergency vehicle. These data may be collected from the route calculation application  98 ( 1 ), the vehicle positioning application  98 ( 2 ), and the sensors  84  in the emergency vehicle. These data are then transmitted to other vehicles in the area (Step  410 ). The data are transmitted using the communications system of the emergency vehicle. In one embodiment, the communications system is the low powered, short-range communications system, described above. 
     The traveling status data are received by the path prediction program  416  which is part of the end-user vehicle warning system  418  (Step  424 ). The path prediction program  416  uses the traveling status data from the emergency vehicle, along with similar data collected by the path prediction program for the vehicle in which the path prediction program  416  is installed, to predict the paths of the emergency vehicle and the vehicle in which the path prediction program is installed (Step  430 ). These predicted paths are compared (Step  434 ) and a probability of an accident is computed (Step  438 ). Based on the level of the probability, a warning or other advice is provided by the path predication program  416  to the vehicle driver (Step  442 ). 
     The process described in FIG. 7 relates to a notification program in the emergency vehicle that transmits traveling status data which are received and used by a path prediction program in an end user&#39;s vehicle to provide the end user/operator with a warning about a possible collision with the emergency vehicle. In order to provide the emergency vehicle operator with a warning about a possible collision, a notification program in each of the end users&#39; vehicles and a path prediction program in the emergency vehicle would perform similar steps. 
     In addition to exchanging data between the emergency vehicle and the other vehicles located around the emergency vehicle, the emergency vehicle also exchanges data with the traffic signal controllers located along the vehicle path. 
     C. Other Alternative Embodiments 
     In the first embodiment described above, the route guidance function was described as being performed by the remote unit navigation system  76  in the emergency vehicle system  32 . In an alternative embodiment, the route guidance function can be performed by the base unit navigation system  40  in the emergency vehicle dispatcher system  30 . Then, data indicating all the required maneuvers are sent to the emergency vehicle system  32  which explicates them at appropriates times and locations using data indicating the emergency vehicle&#39;s position as determined by the vehicle positioning application  98 ( 2 ) located in the emergency vehicle system  32 . 
     In the first embodiment described above, the notification application  50 ( 3 ) in the base unit navigation system  40  determines the expected time of arrival of the emergency vehicle at each of the controllable traffic signals located along the calculated route in order to operate the controllable traffic signals at appropriate times to give the emergency vehicle the right-of-way. If the calculated route is relatively short, the notification application  50 ( 3 ) does not have to determine the expected time of arrival of the emergency vehicle at the controllable traffic signals. Instead, all the controllable traffic signals are operated immediately to provide the emergency vehicle with the right-of-way along the calculated route. 
     In connection with the first embodiment, it was stated that the emergency vehicle warning systems in the end users&#39; vehicles received data concerning the route of the emergency vehicle, and possibly other information such as the traveling status of the emergency vehicle, from the emergency vehicle dispatcher system. In an alternative embodiment, the emergency vehicle warning systems in the end users&#39; vehicles receive data concerning the route of the emergency vehicle and/or the traveling status of the emergency vehicle from the emergency vehicle&#39;s communications system. 
     In the embodiments described above, the traveling status of the emergency vehicle was provided to other vehicles around the emergency vehicle and to traffic signal controllers. The traveling status of the emergency vehicle may also be provided to the emergency vehicle destination, e.g., the hospital, in order to inform staff about the arrival of the emergency vehicle. 
     It is intended that the foregoing detailed description be regarded as illustrative rather than limiting and that it is understood that the following claims including all equivalents are intended to define the scope of the invention.