EP1262934B1 - Method to detect a traffic situation - Google Patents

Abstract

The method involves the following steps: (a) determination of the positions of motor vehicles (b) determination of the corresponding speeds of vehicles (c) determination of a traffic situation criterion from the captured data (d) determination of a limiting velocity (e) comparison of measured vehicle velocities with the limiting velocity (f) determination of the traffic situation criterion by assignment of a given value to the traffic, i.e. free-flowing, if traffic velocity exceeds the limit velocity.

Description

The invention relates to a method for traffic position detection on roads according to the preamble of claim 1.

In traffic telematics traffic monitoring systems are used for traffic situation detection on roads through which traffic information is delivered. For this purpose, traffic data from land vehicles will be identified and used as a basis for recording the traffic situation on the roads. The detected traffic data may be, for example, the position and the speed of one or more land vehicles. These traffic data are determined by suitable sensors and evaluated on the basis of specific parameters. Depending on the collected traffic data, certain values (eg "undisturbed traffic", "stagnant traffic", "dense traffic" or "traffic jam") of traffic condition criteria can then be determined serve as a basis for the generation of a traffic status message, which is then made available to road users (eg traffic reports and travel times via radio or telematic terminals).

The traffic data can be obtained in different ways. For example, the position determination using the GPS ("Global Positioning System") by telematic terminals in land vehicles or by stationary cameras. The speed can be determined by stationary installations or by equipment carried in land vehicles. Essentially, there are two types of data acquisition system: the stationary acquisition system ("SES") with permanently mounted sensors (eg on a motorway) for measuring traffic flow and the floating car data ("FCD") method, in which telematic terminals (so-called "on-board units" (OBU)) are provided as mobile sensors in land vehicles, for example a sampling vehicle fleet. In this case, the same terminal, with which the driver retrieves telematics services, simultaneously serve as a transmitter for traffic data.

In the known methods for traffic situation detection, the traffic data determined are evaluated according to different algorithms. In essence, these algorithms rely on reporting a traffic jam if a certain number of land vehicles in a particular area and time interval are below a set speed value.

A prerequisite for many traffic telematic services is the accurate and up-to-date knowledge of the traffic situation. However, it has been found that the known methods for traffic situation detection do not always provide reliable results. This applies in particular to the traffic situation detection on non-intersection-free roads with traffic lights. Furthermore, the prior art for traffic situation detection in urban road networks includes only central and no terminal-side (FCD) procedures.

In the non-prepublished WO 02/27691 A, a method for the detection of jam is described. At an evaluation device, a GPS receiver, a speedometer and a GSM transceiver unit is connected. The evaluation device comprises a memory unit which stores the position data, a calculation unit which determines the direction of travel from the position data, a comparison unit for comparing the measured speed with a predefined speed limit value, a time measuring device for measuring the time in which the measured speed lies below the speed measurement value , and a connection unit, which is designed such that the current position and the direction of travel of the vehicle is forwarded to the GSM transceiver unit for transmission to a control center when the measured time Time limit exceeded. As a result, a delay-free traffic jam detection should be possible.

The invention has for its object to improve the detection of traffic jams in a method for traffic situation detection of the type mentioned.

The invention is in particular based on the object to perform the detection of traffic congestion as a function of the particular road network.

In particular, the invention is based on the object of improving the detection of traffic disturbances on non-intersection-free roads.

According to the invention this object is achieved by the features listed in the characterizing part of claim 1.

According to the invention, a limit speed is set with which the actual vehicle speed of land vehicles is compared. Depending on this comparison, a value of a traffic condition criterion is then determined, wherein the exceeding of the limit speed is used as a parameter for determining the traffic condition criterion.

Known methods for traffic monitoring on roads are optimized for supra-regional networks, in particular for expressways (and motorways) and designed, for example, for congestion detection. Travels on traffic-free and intersection-free highways are characterized by high speeds. Once the speed is sufficiently long sufficiently small, it can be assumed that a traffic jam, with only stopping at rest areas, gas stations or similar. must be filtered out. This is the basic idea of detecting disturbed traffic (e.g., congestion detection) on highways using the FCD method.

The invention is based on the recognition that such methods are not suitable for use in urban areas. For traffic recording by means of such FCD methods, higher equipment levels are required in conurbations because of lower traffic flows with the same quality than on expressways. Due to the often occurring stopping in agglomerations, eg at an intersection or at a traffic light system, a congestion detection based on falling below a limit speed is not suitable. Depending on the restrictiveness of the parameterization, traffic is erroneously reported as disturbed or undisturbed. The known methods can not quickly and safely differentiate traffic disruptions of undisturbed traffic in agglomerations, since Link lengths, durations of red phases in traffic lights, time losses in Turning maneuvers, etc. can vary within wide limits.

The invention is further based on the finding that a feature of undisturbed traffic exists in agglomerations which has not hitherto been used to distinguish disturbed and undisturbed traffic. This feature consists of a (explicitly or implicitly determined) maximum speed, which can be achieved by all types of vehicles, in places, for example, the statutory maximum speed of 50 km / h in Germany. In this sense, undisturbed city traffic is characterized by the fact that a certain limit speed (for example 40 km / h) is not always exceeded but always exceeded.

In tests with real data, it has surprisingly been found that the method according to the invention can be used very well in all network networks, regardless of whether it is in the supraregional secondary, tertiary or regional area.

Although the inventive method can be used for local, stationary detection (SES), in which the observation of land vehicles with cameras or by aerial observation o.ä. he follows. In particular, however, the method according to the invention is suitable for FCD methods, since it operates with speed profiles of land vehicles.

The method is basically feasible by detecting the vehicle position and the vehicle speed of a single land vehicle. An individual vehicle can find a disturbed traffic, if, for example, a long time from a trailing in front of him tractor, heavily loaded trailer o.ä. is hampered. However, the method according to the invention preferably includes the detection of the vehicle positions and the associated vehicle speeds of several land vehicles, the traffic status messages (eg "undisturbed Traffic ") is determined in dependence on a plurality of the detected vehicle positions and a plurality of the detected vehicle speeds.

The value of the determined traffic condition criterion may include exceeding the limit speed of at least one land vehicle in a particular local area and / or in a certain time interval. For certain traffic reports, it is important to know in which local area and / or in which time interval the speed limit is exceeded so that, for example, a corresponding traffic message can be sent to the road users in this local area and / or in this time interval.

The process according to the invention is preferably used in combination with an FCD process. In this case, the vehicle positions of the land vehicles and the vehicle speeds associated with the respective land vehicle are detected by mobile sensors carried in land vehicles. Such sensors are known, for example, as "on-board units" (OBU).

Preferably, a time period is determined during which the value of the traffic condition criterion is maintained even if there is no limit speed crossing during this time period. As a result, the reporting volume from the vehicles can be reduced without sacrificing quality.

The limit speed which can be predetermined in the method according to the invention is determined by first setting a maximum speed and determining the limit speed as a function of this maximum speed. The specified maximum speed can be the respective legally permissible maximum speed and the determination of the limit speed is based on a specific mathematical relationship, namely the relationship ν _f = αν _H , where ν _{f is} the limit speed, α is a freely selectable control parameter with α <1 and ν _{H is} the specified maximum speed. The maximum speed ν _H can depend on the road class and assume different values, for example, for residential areas, thoroughfares and main roads. Of the Control parameter α can then be varied, for example, to take account of specific local conditions.

The predefinable maximum speed can be set explicitly by selecting the maximum speed legally allowed on the respective road class as the maximum speed. This legal maximum speed can be detected by means of a telematic terminal (OBU) of a land vehicle. For this purpose, the terminal contains a digital map, which is to be taken from the respective valid maximum speed. Furthermore, the specifiable maximum speed can also be obtained from an application-specific table, by means of which road classes and permissible maximum speeds are linked. This is particularly advantageous if the terminal only the street class is shown.

Furthermore, the predefinable maximum speed can be obtained by locating the land vehicle and centrally setting the predefinable maximum speed, with feedback being sent to the land vehicle.

The specifiable maximum speed can be determined implicitly by obtaining the maximum speed by an estimate from the driving data of the vehicle (s). This estimate can be obtained from a specific relationship in which limits of a velocity interval can enter. This relationship can be, for example, ν _H = (ν _- + ν ₊ ) / 2, where ν _{H is} the maximum speed that can be given, and ν _- and ν _{+ are} the limits of a velocity interval [ν _- , ν ₊ ], which is determined by during a certain period of time, a certain percentage of regularly repeated speed measurements lie within this speed interval [ν _- , ν ₊ ].

The determined traffic condition (eg "undisturbed traffic") can be transmitted to the road users by sending a corresponding status message.

Embodiments of the invention are the subject of the dependent claims.

Embodiments of the invention are explained below with reference to the accompanying drawings.

Brief description of the drawings

Fig. 1

shows in a block diagram an embodiment of a method for traffic situation detection.

Fig. 2

shows a typical speed profile of a vehicle with undisturbed traffic in urban areas.

Fig. 3

shows a typical speed profile of a vehicle in disturbed traffic in urban areas.

Fig. 4

shows an application-specific table that links road classes and speed limits.

Preferred embodiment of the invention

The listed embodiments relate to FCD methods in which the land vehicles are equipped with telematic terminals (OBUs). Such OBUs contain, inter alia, a GPS unit for determining the current vehicle position (x, _y), a speed sensor for detecting the current vehicle speed _is ν, a memory for storing data (for example, the current vehicle speed _is ν and the current vehicle position (x, _y)), a transmitter for transmitting data (eg, traffic data) and a receiver for receiving data (eg telematic services). Such terminals are known per se and therefore not described in detail here.

1, the sequence of an embodiment of a method for traffic situation detection is shown in a block diagram. First, a certain non-zero limit speed ν _{f is} set. This is represented by block 10. In this case, a plurality of limit velocities ν _{f, 1} ..., Ν _{f, n} (n ∈ N) can be defined, which are assigned to different local areas [x, y] ₁ ,..., [X, y] _n . It is also possible to define a specific time interval [t ₁ , t ₂ ] in which this limit velocity v _f or limit velocities v _{f, 1} ,..., V _{f, n are} valid, or different such time intervals [t ₁ , t ₂ ] ₁ , ..., [t ₁ , t ₂ ] _n for the different local areas. The determination of the limit velocities ν _{f, 1} ,..., Ν _{f, n} can take place in different ways. It can be done either centrally, for example in a traffic management center or locally in a land vehicle. Some embodiments of the determination of the limit velocities ν _{f, 1} ,..., Ν _{f, n} are described later.

If not already determined in the land vehicle itself, the set limit velocities ν _{f, 1} ,..., Ν _{f, n are} transmitted to the OBU-equipped land vehicles. This is represented by block 12. The transmission takes place by means of wireless communication. In the OBU it is determined in which local area [x, y] _i (i ∈ [1,..., N]) the land vehicle is located (block 14) and the associated limit speed v _{f, i} is determined (block 16) ). The current vehicle speed _is ν is determined (block 18) and with the valid limit velocity ν _{f, i} is compared (block 20). This comparison is repeated with a specific clock frequency (eg 1 Hz).

• Wenn ν_ist größer als ν_f,i ist, wird der Wert des Verkehrszustands-Kriteriums auf "ungestört" gesetzt. Dies ist durch Block 22 dargestellt.
• Wenn ν_ist während einer festgelegten Zeitperiode T (z.B. 20 Sekunden) kleiner als ν_f.i ist, wird der Wert des Verkehrszustands-Kriteriums auf "gestört" gesetzt. Dazu wird zunächst festgestellt, ob ν_ist kleiner als ν_f,i schon während einer längeren Zeitperiode t als T ist (Block 24). Wenn dies nicht der Fall ist ("NO"), dann wird der Wert des Verkehrszustands-Kriteriums auf "ungestört" gehalten (Block 22). Wenn jedoch ν_ist kleiner als ν_f,i, während einer längeren Zeitperiode als T bleibt ("YES"), dann wird der Wert des Verkehrszustands-Kriteriums auf "gestört" gesetzt. Dies ist durch Block 26 dargestellt.

In this way, a traffic condition criterion is determined whose value depends on this comparison, wherein at least one value "undisturbed" is assigned to the exceeding of the limit speed v _f . In the described embodiment, the determination of the value of the traffic condition criterion is as follows:

• If ν _is greater than ν _{f, i} , the value of the traffic condition criterion is set to "undisturbed". This is represented by block 22.
• If ν _is less than ν _fi during a specified time period T (eg 20 seconds), the value of the traffic condition criterion is set to "perturbed". To this end, it is first determined whether ν _is less than ν _{f, i is} already T over a longer period of time (block 24). If this is not the case ("NO"), then the value of the traffic condition criterion is kept "undisturbed" (block 22). However, if ν _is less than ν _{f, i} remains "T" (YES) for a longer period of time, then the value of the traffic condition criterion is set to "perturbed". This is represented by block 26.

The values of the traffic condition criterion are then transmitted to a traffic awareness center via a wireless communication path. The frequency of this transmission is chosen so that as little as possible messages take place. Preferably, a transmission only takes place when there is a change of state of the value of the traffic condition criterion.

In the traffic situation detection center, the traffic data reported by the land vehicles is then evaluated and a traffic status message (eg "undisturbed traffic", "undisturbed traffic during [t ₁ , t ₂ ]", "undisturbed traffic in [x, y] _i ") depending on the value (s) of the traffic condition criteria (s) and optionally the time interval ([t ₁ , t ₂ ]) and the local area ([x, y] _i ). This will be clarified with reference to FIGS. 2 and 3. Fig. 2 and 3 show the instantaneous velocity ν _is a land vehicle as a function of time t. The predetermined maximum speed ν _H and the fixed limit speed ν _f are shown by dashed lines. At a certain time t _A , the land vehicle exceeds the limit speed ν _f . As a result, the value of the traffic condition criterion is set to the value "undisturbed" and a corresponding message ("telegram") is transmitted to the traffic situation detection center. This is shown by an arrow A.

In the further course of the journey shown in FIG. 2, the limit speed ν _f is repeatedly undershot by the land vehicle, ie ν _is becomes smaller than ν _f , however, the duration of the undershoot is always shorter than the fixed time period T, so that the value of the traffic condition criterion maintains the value "undisturbed" and also no message is transmitted to the traffic situation detection center. It is therefore assumed that the traffic is undisturbed, although the speed _is ν of the land vehicle can even assume the value zero. This corresponds, for example, stopping in a red phase of a traffic light system.

In contrast, in the further course of the trip shown in Fig. 3, the limit speed ν _f from the land vehicle for a longer period than the specified time period T (here T = t _C -t _B ) is exceeded. At t _C , the value of the traffic condition criterion is then set to the value "disturbed". Since this results in a change of state of the value of the traffic condition criterion (from "undisturbed" to "disturbed"), a corresponding message transmission also takes place to the traffic situation detection center. This is shown by an arrow C. It is therefore assumed that the traffic is then disturbed.

As already mentioned above, there are various possibilities for determining the limit velocity ν _f . Some such possibilities will now be described by means of examples:

In a first example, the limit speed ν _f is determined by first setting a maximum speed ν _H and determining the limit speed ν _f as a function of this maximum speed ν _H. As stated below, the specified maximum speed ν _H may be the applicable legal maximum speed in the respective local area. The determination of the limit velocity ν _f is in accordance with the equation ν _f = αν _H , where α is a freely selectable control parameter with α <1. The maximum speed ν _{H will} depend on the road class and assume different values, for example for residential areas, thoroughfares and main roads. Since one must assume that most land vehicles do not exceed the legal maximum speed, the control parameter a, the limit speed ν _f over the maximum speed ν _{H is} slightly reduced.

The predetermined maximum speed ν _H can be set explicitly by selecting the maximum speed that is legally permitted on the respective road class as the maximum speed ν _H. This legal maximum speed can be detected using the telematic terminal (OBU) of the land vehicle. For this purpose, the terminal contains a digital map, which is to be taken from the respective valid maximum speed. Furthermore, the specifiable maximum speed can also be obtained from an application-specific table, by means of which road classes and permissible maximum speeds are linked. A section of an example of such a table is shown schematically in FIG. In Fig. 4 it can be seen that the local area [x, y], a federal highway (BAB) with a maximum speed of 130 km / h, the local area [x, y] ₂ a federal highway (B) with a maximum speed of 100 km / h and the local area [x, y] _{3 of} a city street (S) with a maximum speed of 50 km / h is assigned.

Furthermore, the predetermined maximum speed ν _{H can} be obtained by locating the land vehicle and setting the maximum speed centrally, with feedback to the land vehicle. This definition can also be made by tables similar to FIG. 4.

However, the given maximum speed ν _H can also be determined implicitly by obtaining the maximum speed ν _H by estimating from the driving data of the land vehicle (s) itself. This estimate can be obtained by the equation ν _H = (ν _- + ν ₊ ) / 2, where ν _- and ν _{+ are} the limits of a velocity interval [ν _- , ν ₊ ] (eg [63 km / h, 77 km / h ]), which is determined by the fact that during a certain time t _R (eg 10 minutes) a certain percentage p% (eg 85%) of the regularly (eg once per second) repeated speed measurements lie in this speed interval [ν _- , ν ₊ ] , Also, this way of determining the maximum speed provides values that are well-suited to the method.

In the exemplary embodiments listed here, the traffic condition criterion is bivalent with the values "undisturbed" and "disturbed". It should be noted, however, that the traffic condition criterion may of course also have more than two values. For example, several different limit speeds can be set for one and the same local area, whereby not only undisturbed and disturbed traffic but also, for example, undisturbed traffic, stagnant traffic, dense traffic and congestion can be distinguished.

Claims (19)

1. Method for detecting a traffic situation on streets with data detection by means of sensors and data processing using parameters with the steps:

   (a) detecting the vehicle position ((x,y)_act) of land vehicles,

   (b) detecting the vehicle velocity (ν_act) attributed to each respective land vehicle,

   (c) determining a traffic state criterium depending on the detected vehicle position ((x,y)_act) and the detected vehicle velocity (ν_act),
   characterized by

   (d) setting an admissible maximum velocity (ν_H),

   (e) determining a velocity limit (ν_f) by the relationship ν_f=αν_H, wherein α is a free selectable control parameter with α<1,

   (f) comparing the detected vehicle velocity (ν_act) of a land vehicle with the velocity limit (ν_f),

   (g) determining a traffic state criterium where the exceeding of the velocity limit (ν_f) is attributed to a certain value ("undisturbed").
2. Method according to claim 1, characterized by determining a traffic state criterium where the exceeding of a velocity limit (νv) is attributed to a certain value ("undisturbed") in a certain time interval ([t₁,t₂]; [t₁,t₂]_i).
3. Method according to claim 1 or 2, characterized by determining a traffic state criterium where the exceeding of a velocity limit (ν_f) is attributed to a certain value ("undisturbed") in a certain geographical area ([x,y]).
4. Method according to claim 1-3, characterized in that the vehicle positions ((x,y)_act) and the vehicle velocities (ν_act) of several land vehicles are detected and traffic state criteria where the exceeding of a velocity limit (ν_f) is attributed to a certain value ("undisturbed") are determined for several of the detected vehicle positions ((x,y)_act) and several of the detected vehicle velocities (ν_act).
5. Method according to claim 1-4, characterized in that a period of time (T) is set, during which said value ("undisturbed") of the traffic state criterium is maintained even if no exceeding of the velocity limit (ν_f) does not occur during this period of time (T).
6. Method according to claim 1-5, characterized in that the vehicle position ((x,y)_act) of the land vehicles and the respective attributed vehicle velocitiy (ν_act) is detected by stationary sensors.
7. Method according to claim 1-5, characterized in that the vehicle position ((x,y)_act) of the land vehicles and the respective attributed vehicle velocitiy (ν_act) is detected by mobile sensors carried along in the land vehicles.
8. Method according to claim 1-7, characterized in that the set maximum velocity (ν_H) is the legally admissible maximum velocity for the respective street class.
9. Method according to claim 1-8, characterized in that the set or legally admissible maximum velocity (ν_H) is detected by means of a telematic end device (OBU) of a land vehicle.
10. Method according to claim 1-8, characterized in that the set or legally admissible maximum velocity (ν_H) is taken from a table (Fig.4) combining street classes and admissible maximum velocities.
11. Method according to claim 1-8, characterized in that the set or legally admissible maximum velocity (ν_H) is obtained from a feedback from a center.
12. Method according to claim 1-8, characterized in that the set or legally admissible maximum velocity (ν_H) is obtained through estimates from the driving data of a land vehicle.
13. Method according to claim 12, characterized in that the estimate for the set or legally admissible maximum velocity (ν_H) is obtained from the relation ν_H=(ν-+ν₊)/2 wherein ν_-+ν₊ are the limits of a velocity interval [ν_-,ν₊] which is set in that during a certain time (t_R) a certain percentage (p%) of the continuously repeated velocity measurement values are within this velocity interval ([ν_-,ν₊]).
14. Method according to claim 1 - 13, characterized by sending a traffic state message ("undisturbed traffic") depending on the value or the values ("undisturbed") of the traffic state criterium or -criteria.
15. Method according to any of claims 2 - 13, characterized by sending a traffic state message ("undisturbed traffic" during ([t₁,t₂])) depending on the value or the values ("undisturbed") of the traffic state criterium or -criteria and the time interval ([t₁,t₂]).
16. Method according to any of claims 3 - 13, characterized by sending a traffic state message ("undisturbed traffic" in ([x,y])) depending on the value or the values ("undisturbed") of the traffic state criterium or -criteria and the geografic region ([x,y]).
17. Use of the method according to any of claims 1 to 16, for the detection of the traffic situation in streets which are not free of street crossings.
18. Use of the method according to any of claims 1 to 16, for the detection of the traffic situation in streets with an admissible maximum speed.
19. Use of the method according to any of claims 1 to 16, for the detection of the traffic situation in streets with traffic lights.

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