Theoretical Basics

This "hardware" system naturally can’t work on its own. It has to be supplemented by a theoretical basis on which the action taken by the system is determined. We wanted to create the concept of a system which does not merely react but also take preventive action . However this idea led to problems which we can’t fully solve at this state. These problems , mainly mathematical ones and problems in information technology respectively, are still to be overcome.The thoughts developed so far are given as the following :

Presuppositions

The first step is to integrate a map of the city in a grid. By defining an appropriate metric the shortest (quickest) route between two points can be determined.

Beside the coordinates for the actual position there is additional data that has to be considered :

traffic density and traffic flow at the in- and out take of intersections at the time
information on traffic line situation at each intersection (e.g. single/double/triple lines and/or turning lines)
information about connected intersections

At this point the system has to determine the best route for the vehicle dependent on the current traffic situation. Since this problem hasn’t been solved yet the current concept suggests the shortest way to be the one to be taken. After this has been done the traffic lights are switched appropriately to ensure smoothest travel possible for the vehicle. This is done by using the following principle :

"valve principle"

ventils

the vehicles route is drawn in yellow

The traffic lights surrounding the determined route are switched in a way that all vehicles blocking the route can move away while at the same time all intakes along the route are closed thereby ensuring no further traffic moving into the area. We tried to illustrate the effect by using the following picture sequence ( it’s not quite perfect but it may give you an idea of what we’re talking about) :

phase0 phase1 phase2

The traffic along the route is quite dense at the start of the switching. However it is reduced significantly after a short period of time.

Comments and Details

GPS

The requirements on the GPS system to be used are not too high. The average deviation of an ordinary GPS-system is around +/- 30 meters (at a cost of about 150-500 $ ). This is enough to ensure sufficient accuracy of the information on the position and the velocity of the vehicle. These two parameters allow the determination of the distances to oncoming intersections as well as the expected time of arrival. Alternatively a GPS-system with an accuracy of +/- 1 meter may be used if necessary. Today most GPS-system are easily connected to computer interfaces therefore data exchange with a computer system will not be a problem. To ensure the determination of position and velocity in case of GPS-failure the angular changes (i.e. changes in direction) could be measured constantly which, combined with the vehicle’s velocity, also allows determination of all data needed. (An appropriate system is presented in the "Elrad 7/95. The so called "Gyrostar" can measure angular acceleration with a very high accuracy. This system also is not very expensive and would supplement the GPS quite well)

Internal Computer system inside the Vehicle

The system integrated in the vehicle only needs to be a basic one. It has to transform the received data into graphical information presented to the crew. It also supplies the link between the onboard GPS-system and the mobile data net. All this can be done by an ordinary laptop.

Digital Communication Net Services

The mobile data net has to be quite powerful. Preferably it should be a mobile phone which can perform data transmission. Usually these phones are connected to a laptop by a PCMCIA-card that is present in most laptop systems. One communication net that would do the job is the "D2 Net" by "Mannesmann Mobilfunk". This supplier allows data and fax transfer at a rate of 9600 baud. However there are other communication net suppliers that allow data transmission, e.g. the "Modacom" by DeTeMobil (German telecom) which has been optimized for this specific task. Another system planned is "ERMES". It is ment to start it’s work in 1997 with a transmission rate of 6.25 Kbaud. Since the connection through the use of a mobile phone is only used during travel the costs for this also won’t be too high.

Central Computer System at ambulance headquarters

In Germany the head quarter (and it’s computer system) is maintained by a specially trained group of firemen and called the "Leitstelle". Since it’s computer system is connected to a data net already the changes to be done are changes/additions of the software used. One could also establish a connection between the head quarter system and the systems located in most hospitals in the closer surroundings which might improve cooperation.

Hospital’s Computer system

Most hospitals have a computer system which needs to be modified in a similar way to the one mentioned above.

Data Processing

The data processing to be performed by the traffic control system is one of the major tasks. A very big amount of information has to be processed within a short period of time. However considering the performance of today's computer systems this can be managed. Since the computer systems used for traffic control are high performance systems already the changes to be made will probably minor ones. (These systems are used today to process frequently incoming data on traffic density, road capacity, car velocity, traffic jams and so forth to optimize traffic flow).