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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for determining traffic
conditions using stationary data collection devices, e.g., detectors, that
are installed at installation sites along a road network. The data
collection devices collect data concerning traffic conditions at the
respective installation sites in keeping with an established measurement
procedure and then, in keeping with an established reporting procedure,
transmit information derived from this data to a traffic center for
further analysis.
2. Background of Related Art
European patent publication 0 029 201 B1 discloses an interactive dynamic
route guidance system in which specially equipped vehicles engage in
two-way communication with a traffic computer. In this system, beacons
equipped with an infrared transmitter/receiver device are installed at
important junctions in the road network. Vehicles with a corresponding
transmitter/receiver device receive from a traffic computer current
information, as for example the shortest route, with respect to time, to a
desired target or destination. The main sources of information for the
traffic computer are "float-along" sampling vehicles, which move along
with the flow of traffic. The sampling vehicles transmit information, as
for example, the time between important junctions and the waiting or delay
times at stoplights, to the traffic computer. The traffic computer, based
on this information, provides route guidance and traffic direction, for
example, traffic guidance information may be transmitted to a vehicle and
output via a control device on a display in the vehicle.
Another system for determining traffic conditions with detectors installed
in a stationary manner is disclosed in U.S. Pat. No. 5,317,311. The
detectors and associated sensor system, which is located, for example, on
overpasses above the lanes of a highway, measure the average speed of
passing vehicles and determine the number of vehicles that pass in a given
unit of time. This data is transmitted through a data transmission channel
such as a telephone line to a traffic center. In this system, the average
speeds reported by the detectors are transmitted by transmitting devices
from the traffic center to vehicles equipped with receiving devices. The
data is received by the vehicles and graphically displayed on a display as
a map of the sites of particular detectors. Drivers use this information
to detect and avoid current problem areas in the road network or system.
The detectors measure the average speeds so as to continuously monitor the
traffic.
In contrast to the method of ascertaining traffic conditions disclosed in
European patent publication 0 029 201 in which the relevant traffic data
is detected by sampling vehicles and forwarded to data collection
stations, e.g., beacons, which, in turn, transmit all of the data to a
traffic center; the system disclosed in U.S. Pat. No. 5,317,311 collects
the data using stationary sensor systems installed in the detectors
themselves and transmits or reports only a limited amount of the data
collected or detected by the detectors to the traffic center. In
particular, data is transmitted or reported to the traffic center only
when the average speed of the passing vehicles detected by the detectors
during a certain time period falls below a preestablished threshold value,
as for example a threshold value of approximately 50 km/h. As a result,
the burden and bandwidth of the communication channel for data
transmission is substantially reduced. This reduction in data
transmission, however, disadvantageously limits the use of the system to
situations in which there is very heavy traffic, e.g., traffic jams or
similar situations. Thus, this traffic detection system is not suitable
for detecting conditions in which the traffic is moderate or the roads are
completely empty because of the limited reporting or transmission of
collected data. The detection of conditions in which there is moderate
traffic or in which the roads are completely empty is only possible if all
of the information or data is reported which would require a corresponding
increase in communications expenditure between the detectors and the
traffic center.
The object of the present invention is therefore to provide a process for
determining traffic conditions which establishes relatively inexpensive
communications between the stationary detectors and the traffic center and
is not limited in the information being observed or for use in only
particular types of traffic conditions.
SUMMARY OF THE INVENTION
The present invention is directed to a process for determining traffic
conditions using data collection devices, e.g., detectors, installed in a
stationary manner at installation sites along a road network. The data
collection devices collect data concerning the traffic conditions at the
installation site of each respective data collection device in accordance
with an established measurement procedure and, in accordance with an
established reporting procedure, forward the information derived from this
data to a center for ascertaining the traffic condition for further
analysis. The analysis performed at the center comprises, for example,
deriving a current traffic report and/or deriving historical traffic
information and/or issuing traffic prognoses and/or identifying events
that characterize the traffic conditions. The center then transmits to the
data collection devices at least a portion of the results of the analysis.
Thereafter, each particular data collection device, on the basis of these
transmitted results, adjusts or modifies its measurement procedure and/or
its reporting procedure in the manner of a learning system.
The results of the analysis of the center are selected in reference to the
installation sites of individual data collection devices or a group of
data collection devices. This selection may be performed at the traffic
center or may be performed in the particular data collection device by
filtering the transmitted results.
From time-to-time a currently valid graph curve for traffic-relevant
measurement variables is derived in the traffic center and transmitted to
a data collection device. The particular data collection device then
reports to the center only detected deviations from the currently valid
graph curve. The graph curve may be transmitted to the data collection
device as a series of points of a function curve. Alternatively, a
plurality of standardized graph curves may be stored in the data
collection device whereby the center prescribes a graph curve for a data
collection device by transmitting a code that is unambiguously associated
with one of the stored graph curves. The graph curves may be based on
classified weather conditions and/or traffic-relevant events.
Traffic conditions predicted for a particular installation site are
transmitted to the data collection device in question. Assumptions about
the current traffic conditions at an installation site are forwarded by
the traffic center to the particular data collection device for checking,
and detected deviations are reported back to the center by the data
collection device. The center upon finding characteristics that indicate a
problem upstream from the installation site of a data collection device or
impending traffic congestion at the installation site (early indicators)
sends these to the data collection device in question.
The present invention is also directed to a system for determining traffic
conditions comprising a center with an electronic data processing unit for
ascertaining the traffic condition and a communications unit. The system
also includes a plurality of data collection devices installed at the side
of a road network and a bidirectional communications channel for
transmitting information from the data collection devices to the center.
Each data collection device comprises a sensor system for collecting
measurement values, an electronic data processing unit, a communications
unit and an electric power supply unit. The electronic data processing
device of each data collection device is programmed in such a way as to
adjust, in the sense of a self-learning system, the measurement procedure
and/or the reporting procedure of the data collection device on the basis
of the results of the center in the framework of ascertaining the traffic
condition.
Standardized graph curves for traffic-relevant measurement variables are
stored in the data processing device of the data collection devices. Each
graph curve is identifiable in the data collection device by a unique code
sent from the center. The data processing device is programmed as a
comparator to recognize substantial deviations of the current values of a
measurement variable from a graph curve preestablished by the center.
Alternatively, the system may be constructed so that each data collection
device has a filter for the selection of results that are transmitted from
the center and intended only for an individual data collection device or
one group of data collection devices.
In the present invention, the traffic information to be transmitted or sent
to drivers includes, in addition to detected average speeds, traffic
information obtained by analyses of the detected data and other applicable
information. In particular, these analyses include, for example, the
derivation of current and/or historical traffic data and/or the issuing of
traffic prognoses and/or the identification of events characteristic of
traffic conditions. The traffic center transmits to the data collection
devices at least a portion of the results of its analyses of the data
received from the data collection devices. On the basis of the results of
the analyses transmitted to the data collection devices from the traffic
center, the measurement and/or reporting procedures or operations of a
particular data collection device which collects data may be adjusted or
set to establish new procedures in a type of learning process or
operation. The data collection devices receive from the traffic center the
same information transmitted by the center to drivers of vehicles using
its services. This information is used to modify the procedures in order
to optimize the data being collected and reported by the data collection
devices. The measurement operation or procedure may be modified based on
such factors and considerations, as for example, whether all measurement
or detection of data should be suspended permanently, whether all
measurement or detection of data should be temporarily suspended, what
type of average values are to be detected or found and over what period of
time. In addition, the reporting operation or procedure may be modified
based on such factors, as for example, the dependence of data transmission
on the existence of certain events and the preestablishment of certain
time intervals between individual data transmissions. Optimization of data
transmission is realized by providing the traffic center at all times with
as much traffic data as is objectively required or needed, while keeping
the expense for data transmission, and in particular, the burden on the
communications channels, as small as possible.
The results of analyses by the traffic center are selectively transmitted
to individual data collection devices or a group of data collection
devices. This selection may be performed at the traffic center. In an
alternate embodiment or modification, the selection of results may be
performed in a particular data collection device by filtering means, as
for example, is known and used in digital radio receivers (RDS/TMC=Radio
Data System/Traffic Message Channel).
The traffic center from time-to-time produces a current graph curve of
traffic-relevant measurement variables, for example, average speed, and
transmits this curve to the particular data collection device to which the
variable is applicable or appropriate. Thereafter, the data collection
device transmits or reports to the traffic center only subsequently
collected measurement variables or information which deviate at all, or
alternatively deviate in excess of a predetermined acceptable range, from
the current graph curve. As a result, the volume of information or data
transmitted to the traffic center is reduced despite changes over time in
the measurement variables collected. This reduction in data transmitted to
the traffic center is based on the underlying principle that the
transmission of data from a data collection device to the traffic center
is completely superfluous or redundant so long as the "model" that the
center has of the current traffic condition at that particular measurement
point does not differ substantially from reality, that is from the values
or data being detected This comparison may be made by the particular data
collection device itself when the "model" of the center, i.e., the graph
curve for a given measurement variable, is stored in a memory device in
the data collection device or is transmitted to the data collection device
as a series of points of a function curve. In an alternate embodiment,
standardized graph curves of the traffic-relevant measurement variables
for typical traffic conditions are stored in the data collection devices
and a standardized graph curve is selected in response to unique codes
associated with the stored graph curves which are transmitted by the
traffic center. The various graph curves are based on such factors as
weather conditions (e.g., dry weather, rain, ice/snow), and/or
traffic-relevant events (e.g., road construction) and/or large public
events (e.g., trade fairs, football games, etc.).
In addition, the traffic prognosis for a particular installation site is
transmitted to the corresponding data collection device in order to
optimize the measurement and/or reporting behavior of the data collection
device. This operation is similar to the process variant in which graph
curves are preestablished for the data collection devices, because both
operations are based on future expectations of the traffic center. The
process according to the invention also transmits assumptions about
current traffic conditions at an installation site from the traffic center
to a particular data collection device for checking or confirmation of the
traffic condition. In the event that actual traffic conditions
substantially deviate from the assumptions the data collection device will
transmit an appropriate message to the traffic center.
Processes for determining traffic conditions are known in which the data
collection devices use a reporting procedure which depends on locally
recognizable traffic conditions. In other words, single or periodic
reports to the traffic center are triggered when the local conditions
exceed or fall below certain threshold values. These methods, however, are
relatively insensitive to special local features (e.g., sections of road
with hills or curves), to measurement values that indicate user-relevant
phenomena at some distance from the data collection device (e.g., traffic
problems upstream from the measurement point, to temporary external
influences (e.g., weather conditions) or to distinguishing features of
traffic conditions that have different causes but similar symptoms (e.g.,
traffic congestion at construction bottlenecks and "shifting overload
congestion"). However, the aforementioned features and factors are
reflected in characteristic movements or jumps of the working point in the
fundamental diagram, which shows the interrelations of speed, traffic flow
(e.g., vehicles per hour), and traffic density (e.g., vehicles per unit of
road length). The data collection devices of the present invention, after
completing a learning phase, identify traffic variables or information
which are relevant and measure or detect and report or transmit to the
traffic center only relevant-traffic information. Initially during the
learning phase, the entire scope of the collected measurement data is
transmitted to and analyzed at the traffic center. The analysis may be
performed using, for example, conventional statistical methods, methods
based on the training of neural networks or "fuzzy" algorithms. The
results of the analyzes are transmitted to the data collection devices
which recognize or identify traffic features or data which is to be
reported to the traffic center. During this learning process, which is
determined based on analyses over a relatively long period of time, the
data collection devices simultaneously receive historical traffic
information which is used to recognize the initial indicators of
user-relevant events. The user-relevant events are, in turn, forwarded to
the traffic center and are used to assess the traffic condition.
The current traffic information is also used to reduce the transmission of
redundant measurement data. Information may be provided to a data
collection device by sources in the process or, alternatively, may also
originate from sources outside of the present inventive process which is
checked or confirmed by the appropriate data collection device. The
information provided to a data collection device includes not only reports
about traffic problems that exist or have been cleared up, but also
includes predictions made by the traffic center that take into account
external factors known in advance, such as weather conditions or
construction plans, and may be used by a specific data collection device
to recognize deviations to be reported to the traffic center. In this
context, user-relevant deviations include unexpected problems that occur
and expected problems that do not occur. The traffic information sent to a
data collection device for checking or confirmation is not necessarily
limited to centrally collected data on current conditions and may include
predictions for a short or brief time period relative to a daily graph
curve. The traffic center detects or identifies early indicators, that is
characteristics that indicate a problem upstream from the installation
site of a data collection device or point to impending congestion at its
installation site, and transmits this information to the appropriate data
collection device.
Other objects and features of the present invention will become apparent
from the following detailed description considered in conjunction with the
accompanying drawings. It is to be understood, however, that the drawings
are designed solely for purposes of illustration and not as a definition
of the limits of the invention, for which reference should be made to the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, wherein like reference numerals denote similar elements
throughout the several views:
FIG. 1 depicts the system for determining traffic conditions using
stationary data collection devices of the present invention; and
FIG. 2 diagrammatically depicts the basic functions of the traffic center
and data collection device of the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
An illustrative example of a system for detecting a traffic condition
according to the present invention is shown in FIG. 1, including a traffic
center 1 and three data collection devices 8. It should be noted that
although three data collection devices 8 are illustrated and described it
is within the intended scope of the invention to construct the system with
one or more data collection devices. The traffic center 1 comprises an
electronic data processing unit 2 and a communications unit 3. Information
and data is transmitted between the traffic center 1 and the data
collection devices 8 over a bidirectional or two-way communications
channel 9, as for example, telephone lines, but is preferably a wireless
network such as a mobile phone wireless network. The data collection
devices are installed at roadside, as for example, on overpasses above
highways or roadways in a road network, and are designed to collect or
measure relevant data which is transmitted or reported to the traffic
center 1 where the data is analyzed to determine the traffic condition.
Each data collection device 8 includes a communications unit 4, an
electronic data processing device 5, a sensor system 6 for collecting
measurement values and an electric power supply unit 7. In a preferred
embodiment the power supply unit 7 is a battery-buffered solar cell unit.
The sensor system 6 comprises conventional sensors such as active or
passive infrared sensors or as microwave sensors and preferably includes
sensors based on different measurement principles in a single data
collection device 8. Relevant data collected at the data collection device
is transmitted by the communications unit 4 to the traffic center 1 over
the communications channel 9 in order to determine the traffic condition.
In addition, at least some of the results of the data analyses from the
traffic center is transmitted by the communication device 3 to the data
collection devices 8 over the bidirectional communications channel 9.
Based on results of the data analyses received from the traffic center 1,
the data processing devices 5 of the data collection devices 8 adjust
their measurement procedures and/or reporting procedures in a type of
self-learning phase or operation and change their procedures as needed in
order to optimize overall transmission efficiency.
In another embodiment of the invention, standardized graph curves for
traffic-relevant measurement variables are stored in a memory or storage
device (not shown separately) of the data processing unit 5 of the data
collection device 8. Particular standardized graph curves are selected in
response to unique codes associated therewith which are transmitted from
the traffic center 1. As a result, the traffic center 1 selects or
identifies a particular graph curve to a particular data collection device
8 based on the associated unique code without having to transmit a series
of points or large number of individual values which characterize the
graph curve in the particular case. The data processing device 5 is
programmed as a comparator in order to recognize any deviations or
deviations exceeding or greater than a predetermined acceptable threshold
or range between currently collected values for a measurement variable and
a graph curve preestablished by the traffic center 1. Thus, the reporting
procedures of the respective data collection devices 8 may be optimized in
that data is transmitted via the communications channel 9 to the traffic
center 1 only when deviations are detected. When deviations are not
detected, data transmissions from the data collection devices 8 to the
traffic center 1 is stopped or prevented. In an alternative embodiment of
the invention, each of the data collection devices 8 includes a filter for
selecting events that are transmitted by the traffic center 1 and intended
only for individual data collection devices 8 or a group of data
collection devices 8. Thus, the operation or performance of an individual
data collection device 8 or a group of data collection devices 8 installed
along a certain stretch of roadway or highway, for example, may be
deliberately influenced by the traffic center 1. The data collection
devices 8 determine by comparing the detected traffic data with that of
the traffic information distributed to drivers by the traffic center 1
whether the traffic condition determined by the traffic center 1 matches
or agrees with the actual traffic condition at the installation sites. If
the two sets of information do not match, then the transmission of data
from the data collection device 8 to the traffic center 1 is initiated
immediately to correct the error.
The scope of data transmissions required to determine the traffic condition
in a road network is therefore substantially reduced using this present
inventive process and apparatus. This reduction in data transmission is
due in part to the data collection devices 8 which continuously receive
and assess at least part of the analyses results of the traffic center
distributed to the drivers concerning the ascertained traffic condition as
well as targeted individual information.
FIG. 2 shows some of the functions and operations of the process according
to the invention for the two main components, the traffic center 1 and the
data collection device 8. Since the functions of each data collection
device 8 is substantially the same only one data collection device 8 is
illustrated and described in FIG. 2. The information or communication flow
between components is symbolized by arrows. A suitable sensor system 6
measures traffic-relevant data, e.g., current speeds of passing vehicles,
and the measured data is then preprocessed in the data processing device 5
of the data collection device 8. Preprocessing of the collected or
measured data may, for example, comprise finding an arithmetic mean value
over a certain observation period or compressing the collected data. The
data collection devices may be programmed based on user-relevant events
that have been defmed in advance by the traffic center 1. In addition, the
data processing device 5 of the data collection device 8 may also be
programmed to compare "sensor knowledge" (measurement values from a
certain period up to the present) with "system knowledge" (current traffic
reports, traffic predictions and historical information in the form of
graph curves, for example) and then report deviations, for example, which
are of immediate importance in assessing the current traffic condition or
supplement and/or correct the "system knowledge." Information is
communicated or transmitted between a communications unit 4 of the traffic
center 1 and the communications unit 3 of the traffic center 1 via a
two-way communications interface or bidirectional communications channel.
The data processing device 2 in the traffic center 1 is labeled "traffic
model". This data processing device receives the collected data from the
data collection device 8 and analyses this information to determine or
ascertain the traffic condition. As shown in FIG. 2, the results of the
analyses of the data processing unit 2 of the traffic center 1 may
include, for example, generated traffic reports, traffic prognoses, graph
curves and/or identification of user-relevant events. These analyses
results are then transmitted to the drivers of the vehicles to be used as
guidance. Moreover, at least a portion of the results of the analyses of
the traffic center 1 are also transmitted to particular data collection
devices 8 over the communications channel 9 to modify or influence the
measurement and/or reporting procedures of the data collection devices and
thereby reduce the amount of transmitted data.
Thus, while there have been shown and described and pointed out fundamental
novel features of the invention as applied to preferred embodiments
thereof, it will be understood that various omissions and substitutions
and changes in the form and details of the devices illustrated, and in
their operation, may be made by those skilled in the art without departing
from the spirit of the invention. For example, it is expressly intended
that all combinations of those elements and/or method steps which perform
substantially the same function in substantially the same way to achieve
the same results are within the scope of the invention. Substitutions of
elements from one described embodiment to another are also fully intended
and contemplated. It is also to be understood that the drawings are not
necessarily drawn to scale but that they are merely conceptual in nature.
It is the intention, therefore, to be limited only as indicated by the
scope of the claims appended hereto.
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