Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Traffic analysis or control of surface vehicle
Reexamination Certificate
2001-04-16
2003-07-01
Louis-Jacques, Jacques H. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Traffic analysis or control of surface vehicle
C701S118000, C701S119000, C340S909000, C340S920000, C340S934000, C348S148000, C348S149000, C382S104000
Reexamination Certificate
active
06587779
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German priority document 198 35 979.9, filed Aug. 8, 1998 and PCT International Patent Application No. PCT/EP99/05689, filed Aug. 6, 1999, the disclosures of which is expressly incorporated by reference herein.
The invention relates to a method for monitoring traffic states in a road traffic system and to a method for controlling vehicle inflow as a function of the traffic states.
Various methods of this type are known in the field of traffic control technology. The traffic states are sensed at a given time for a particular monitoring point of the road traffic system, using measuring equipment with appropriate sensors. Alternatively, or in addition, the traffic states at the monitoring point are predicted in advance. An appropriately configured traffic control computer which is normally used for this purpose, suitably evaluates the measured data, and preferably also empirically determined predicted values for the traffic states to be expected at the particular monitoring point at a time in question. The traffic state information which is determined in this way can then be used for various purposes; for example for travel time prediction, for dynamic route planning and for traffic-controlling intervention such as controlling the vehicle inflow at entries into a respective section of the traffic system. The term “control” is used above, for the sake of simplicity, in its wider sense which includes both open-loop and closed-loop control systems.
Investigations have shown that the traffic states in road traffic systems can be divided into three significantly different types; specifically free traffic flow, synchronized traffic flow and wide moving traffic jams. See B. S. Kerner and H. Rehborn, Experimental features and characteristics of traffic jams, Phys. Rev. E, Vol. 53, page 1297, 1996 and B. S. Kerner and H. Rehborn, Experimental properties of complexity in traffic flow, Phys. Rev. E, Vol. 53, page R4275, 1996. Free traffic flow is understood here to be the state in which any road user can freely select its velocity and any desired overtaking maneuvers are possible. The wide moving traffic jams state signifies stationary vehicles with maximum traffic density on the road. Synchronized traffic flow, also referred to as stop-and-go traffic, constitutes a traffic state between free traffic flow and the wide moving traffic jams state, in which the traffic density (i.e., the traffic flow) may be relatively large but is significantly higher, and thus the velocity of the vehicles is significantly lower, than in free traffic flow, which very greatly increases the trip time. Owing to the higher traffic density, overtaking maneuvers are virtually impossible; for this reason the velocity of the vehicles at one location on the different lanes of a multilane road (expressway) is slow-moving when all the lanes are going in the same direction.
There are numerous known methods for detecting the wide moving traffic jams state by analyzing locally measured traffic data, including disruption detection and analysis. See, for example, German patent document DE 196 47 127 A1 and the literature referred to in it.
The control of the inflow of vehicles, also referred to as inflow metering, constitutes one of the possible ways of controlling the traffic flow when traffic disruption is detected or predicted, and thus preventing the occurrence of disruption or in any case as far as possible restricting its consequences in order to minimize increasing trip times and to maximize the efficiency of the roads. There are numerous known methods for inflow metering for entries to expressways. For example, a simple strategy frequently used in the USA has been to simply close off the entries when traffic comes to a standstill; but methods have also been used there in which the total of the inflow and upstream measurement in comparison with the downstream capacity of the road has been used as a criterion for restricting inflow, see L. E. Lipp, L. J. Corcoran, A. H. Hickman, Benefits of central computer control for Denver ramp-metering system, Transportation Res. Board No. 1320, Washington D.C., 1991 and N. L. Nihan, M. G. H. Bell, A predictive algorithm for real-time ramp control system, ITE Journal, June 1992.
In Great Britain a multilayered algorithm has been used for inflow control. In this algorithm the road capacities were monitored and an inflow control was carried out at excessively low velocities, the space/time profile of the waves of traffic density being tracked and the queue length of backed-up vehicles being used. See D. Owens, M. J. Schofield, Access control on the M
6
motorway: evaluation of Britain's first ramp-metering scheme, Traffic Engineering+Control, page 616, 1988. In the Netherlands, on the other hand, a concept of individual metering for vehicle circulation times between 4.5 seconds and 12 seconds with the latter value as the maximum possible value was investigated. This concept corresponds to metering between 300 vehicles/h and 800 vehicles/h. See H. Bujin, F. Midelham, Ramp metering control in the Netherlands, Road Traffic Control May 1990 and Projektbericht DRIVE I Project V 1035 CHRISTIANE—Isolated Ramp Metering: Real Life Study in The Netherlands, Deliverable 7a, March 1991 of the EU project CHRISTIANE.
In France, CHRISTIANE was developed and used within the EU project and subsequently the ALINEA algorithm was developed and used in field trials in Germany (and in Germany in a modified form with the traffic density instead of the degree of occupancy). See the project report DRIVE I Project V 1035 CHRISTIANE—Isolated Ramp Metering: Real Life Study in France and Software Prototypes, Deliverable 7b, October 1991 and P. Stöveken, Verfahren zur Steuerung des Verkehrsablaufs auf Stadtautobahnen mittels Geschwindigkeits- und Zuflu&bgr;regelung, Stra&bgr;enverkehrstechnik June 1992.
Both the wide moving traffic jams state and the state of synchronized traffic flow are highly significant for maintaining the greatest possible efficiency of road use. The trip times in the case of synchronized traffic flow are significantly increased in comparison with free traffic flow, which is undesirable in itself, and in addition for associated applications, for example telematics applications. There is therefore a need for a method for detecting reliably the state of synchronized traffic flow and distinguishing in particular from the state of free traffic flow so that this information can then be suitably used for inflow metering which exploits the efficiency of the road in the best possible advantage and/or for short-term prediction of trip times.
One object of the invention is to provide a method for monitoring traffic states of the type described above.
Another object of the invention is to provide a vehicle inflow control method which uses such monitoring method and with which the traffic transitions can be reliably monitored, and when necessary estimated in advance, in particular with regard to phase transitions between free traffic flow and synchronized traffic flow and/or with regard to wide moving traffic jams states.
Finally still another object of the invention is to provide a method and apparatus which achieves a high degree of efficiency of a monitored section of the traffic system, with relatively little expenditure.
These and other objects and advantages are achieved by the method and apparatus according to the invention, in which current or predicted traffic states are determined for one or more points and a distinction is made between the three types of traffic states: free traffic flow, synchronized traffic flow and wide moving traffic jams. Vehicle inflow into the traffic system is then controlled as a function of the detected traffic states. The state monitoring method is configured to detect or predict phase transitions between free traffic flow and synchronized traffic flow and/or wide moving traffic jams states, by means of specified criteria. Furthermore, according to the invention the vehicle in
Kerner Boris
Rehborn Hubert
Crowell & Moring LLP
Daimler-Chrysler AG
Louis-Jacques Jacques H.
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