U.S. patent number 3,906,438 [Application Number 05/332,258] was granted by the patent office on 1975-09-16 for system for monitoring traffic conditions in connection with the control thereof.
This patent grant is currently assigned to Siemens Aktiengesellschaft. Invention is credited to Dietrich Kohnert.
United States Patent |
3,906,438 |
Kohnert |
September 16, 1975 |
System for monitoring traffic conditions in connection with the
control thereof
Abstract
A system for monitoring traffic flow on streets having at least
two traffic lanes free from oppositely directed traffic,
particularly highways, wherein each traffic lane can be monitored,
at least at one common location, by respective vehicle detectors,
in which the magnitudes of time intervals between successive
vehicles at the associated detector are measured, and mean values
thereof are formed, together with mean values of another
representative corresponding magnitude between successive
intervals, with the values being stored in respective memories and
supplied therefrom over linking means with a difference-forming
device, together with similar values from other detectors, in
predetermined timing with the output of the difference-forming
device providing an evaluatable magnitude related to the traffic
flow.
Inventors: |
Kohnert; Dietrich (Eichenau,
DT) |
Assignee: |
Siemens Aktiengesellschaft
(Berlin & Munich, DT)
|
Family
ID: |
5836247 |
Appl.
No.: |
05/332,258 |
Filed: |
February 14, 1973 |
Foreign Application Priority Data
|
|
|
|
|
Feb 17, 1972 [DT] |
|
|
2207487 |
|
Current U.S.
Class: |
340/934;
340/941 |
Current CPC
Class: |
G08G
1/01 (20130101) |
Current International
Class: |
G08G
1/01 (20060101); G08G 001/01 () |
Field of
Search: |
;340/31A,31R,37,38R,38L,41R ;235/150.24 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Claffy; Kathleen H.
Assistant Examiner: Myers; Randall P.
Attorney, Agent or Firm: Hill, Gross, Simpson, Van Santen,
Steadman, Chiara & Simpson
Claims
I claim as my invention:
1. A system for monitoring traffic flow on streets having at least
two traffic lanes free from oppositely directed traffic,
particularly highways, wherein each traffic lane can be monitored,
at least at one common monitoring location, by respective vehicle
detectors, comprising for each detector a measuring system for
deriving representative magnitudes of time intervals between
successive vehicles at the associated detector, means for forming
values representative of such magnitudes and comprising a mean
value device to which interval magnitudes are supplied, and a
memory for storing successive mean interval values derived from
said mean value device, the output of said value forming means
supplying such representative values, comparison means for
effecting a predetermined comparison function between a plurality
of representative values, and means operatively connecting
corresponding outputs of the respective value-forming means of a
plurality of said detectors to said comparison means for comparison
of the respective representative values of said detectors, the
output of said comparison means being operative to provide an
evaluatable output magnitude related to the traffic flow.
2. A system according to claim 1, comprising in further
combination, timing means, operatively connected with said
measuring system, operable to simulate a vehicle by providing an
impulse if time intervals of a certain magnitude are exceeded.
3. A system according to claim 1, wherein said comparison means
comprises a quotient-forming device to which said representative
values are supplied.
4. A system according to claim 1, wherein the representative values
supplied to said comparison means are from different detectors of
the same monitoring location.
5. A system according to claim 4, wherein in further combination, a
further means forming device is provided, to which the output of
said said comparison means is supplied, the output value of which
provides an evaluatable output magnitude.
6. A system according to claim 5, comprising in further combination
a further memory for storing the output values of said further mean
value forming device, further comparison means to which the output
of said further memory is supplied, along with a similar output
from another monitoring location, the output of such further
comparison means providing an evaluatable output magnitude.
7. A system according to claim 6, wherein said further comparison
means comprises a difference-forming means, the output of which
supplies an evaluatable output magnitude.
8. A system according to claim 1, wherein said value-forming means
for each vehicle detector includes means, to which are supplied
other magnitudes different from said first-mentioned magnitudes,
but also representative of time intervals between respective
vehicles at the associated detector, operative to modify such
second magnitudes to form second corresponding representative
values, a second mean value forming device to which said
last-mentioned representative values are supplied, a second memory
for storing successive mean values derived from said second means
forming device, and linking means for effecting a predetermined
comparison function between mean values in said second memory with
the mean interval values stored in said first memory of the
associated detector, the output magnitude of said last-mentioned
means comprising the output of said value-forming means and
supplied to said comparison means as the representative value of
such detector, which is to be compared with a corresponding value
from another one of said detector.
9. A system according to claim 8, wherein the representative
magnitude supplied to said modifying means comprises a difference
value between the preceding mean interval value and the next
interval value.
10. A system according to claim 8, wherein said linking means
comprises a product-forming device.
11. A system according to claim 8, wherein said modifying means
comprises a product forming device operative to form the square of
such other representative magnitudes.
12. A system according to claim 8, wherein said modifying means
comprises a product-forming device operative to form the square of
such other representative magnitudes.
13. A system according to claim 8, wherein said first means value
forming device is operable to also provide the difference value
between a newly received interval magnitude and the mean value of
the immediately previous interval, which difference value is
modified by said modifying means and forms said second
representative corresponding magnitude and which is supplied to
said second mean value forming device, the linking means between
the respective memories therefor and said comparison means
including a product-forming device to which the output values of
such memories are supplied, said comparison means comprising a
quotient-forming device to which the output value of said
product-forming device is supplied, and to which is also supplied
the output value derived from another of said detectors, the output
value of such quotient-forming device being supplied to a further
mean value forming device, the output value of which is supplied to
one input of further comparison device means, the other input of
which is connected by further linking means to memories associated
with a plurality of other detectors.
14. A system according to claim 13, wherein means are provided for
the respective mean value forming devices, for adding the product
of a selected factor and the difference between the previously
respectively stored mean value and the new measured value, to the
stored old mean value.
15. A system according to claim 13, comprising in further
combination, timing means, operatively connected with said
measuring system, operable to simulate a vehicle by providing an
impulse if time intervals of a certain magnitude are exceeded.
16. A system according to claim 13, wherein the output value
supplied from said first comparison means to said further
comparison means, is also supplied to additional comparison means,
to which is supplied the immediately previous corresponding value
from said last-mentioned further mean-forming device, the outputs
of both said further and additional comparison means comprising
evaluation magnitudes related to the traffic flow.
17. A system according to claim 16, wherein each of the
mean-forming devices associated with the mean interval magnitude
and the mean difference value has operatively connected thereto
means for altering the associated difference value, between a new
magnitude and the previous value, by a predetermined factor, the
factors for the respective mean-forming devices having different
values.
18. A system according to claim 17, wherein said modifying means
comprises a product-forming device operative to form the square of
such other representative magnitudes.
19. A system according to claim 18, wherein said difference forming
device is operable to evaluate at predetermined times, the contents
of memories of a monitoring location, and operatively connected
with at least two associated traffic detectors.
20. A system according to claim 18, wherein said difference forming
device is operable to evaluate the contents of memories of two
monitoring locations which can be simultaneously supplied, under
control of the timing means, and operatively connected with at
least two associated traffic detectors.
21. A system according to claim 18, wherein the memories of a
single monitoring location are interlinked by means of a
quotient-forming device during the evaluation of only a like type
of mean time values, and both memories of a detector are
interlinked by means of a product forming device, in the case of a
common evaluation of different types of mean time values.
22. A system according to claim 18, wherein means are provided for
the respective mean value forming devices, for adding the product
of a selected factor and the difference between the previously
respectively stored mean value and the new measured value, to the
stored old mean value.
23. A system according to claim 13, wherein said modifying means
comprises a product-forming device operative to form the square of
such other representative magnitudes.
Description
BACKGROUND OF THE INVENTION
The invention is directed to a system for use in depicting and
controlling traffic operations on streets utilizing at least two
traffic lanes which are free from traffic in the opposite
direction, such as highways, and from which desired indications and
control of traffic may be effected, with each traffic lane being
monitored by a traffic detector at least at one common monitoring
or measuring location. As traffic continually increases in density,
even on highways, traffic surveilance and monitoring, similar in
manner to that utilized in cities becomes of greater and greater
importance, particularly in connection with possible control by
means of speed indicators and other devices. It is known in the
prior art to direct a part of the traffic to exits when an
undesirable density is reached, whereby relief can be effected. It
has heretofore been deemed necessary to detect the traffic on the
highway, if possible over the entire range or distance, and it is
already known to direct television cameras at suitable observations
points and to channel the evaluation information to a central
office. As control personnel are required in such operations, other
solutions have been sought, i.e., measuring or monitoring locations
with traffic detectors at suitable intervals to detect vehicles
entering or leaving such areas and to utilize data so obtained in
the formation of conclusions as to the traffic density and other
traffic conclusions from differences therebetween. As previously
mentioned, with the first method, substantially continuous
observation by personnel is required, but while the second method
does not require such observation, it is possible with such system
not to detect vehicles while they are driving in or out, whereby
entirely erroneous information will be transmitted due to the
addition of errors.
SUMMARY OF THE INVENTION
The invention is directed to the production of a system for
monitoring traffic on streets where at least two traffic lanes are
free from traffic in the opposing direction, preferably a highway,
which is simple in construction and does not contain the above
referred to disadvantages, and which will make accurate reflections
of the traffic flow on the highway.
These results that are achieved by the utilization of a traffic
detector for each traffic lane, at at least one common monitoring
location, and utilizing a measuring device for determining the
duration of time intervals between vehicles. Means are provided for
determining the mean value of such intervals and also the mean
value of an additional representative magnitude such as the
difference between a first monitored interval and a newly monitored
interval, preferably modifying such additional value, for example
by squaring the same, prior to deriving the mean value thereof and
with the employment of associated memories for each traffic
detector, and a difference-forming device, the contents of such
memories along with the associated memories of other traffic
detectors, being interlinked over product-forming devices, under
the control of timing means, will result in the formation by the
difference-forming device of an evaluatable magnitude relating to
the traffic flow, and by means of which obstructions to the normal
flow, either stationary or slowly moving, may be ascertained.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings wherein like characters indicate like or
corresponding parts:
FIG. 1 schematically illustrates a section of a roadway and
associated traffic detectors;
FIG. 2 is a circuit diagram of a system embodying the present
invention with, however, circuit details individual to the
respective traffic detectors being illustrated only for traffic
detector 1;
FIG. 3 is a chart illustrating changes in traffic distribution;
and
FIG. 4 is a graph of the favorable operational range of the
system.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates a section SA of a highway, comprising two
traffic lanes, F1 and F2, having a single traffic direction as
illustrated by the arrow P. Two monitoring locations A, B are
employed, provided with traffic detectors 1-4, detectors 1 and 3
being associated with lane F1 and detectors 2 and 4 being
associated with lane F2, with the distance between the locations A
and B being approximately 500 to 1,000 meters. The four traffic
detectors 1-4, in conjunction with the circuit shown in FIG. 2,
permit the monitoring of the traffic conditions along the section
SA, by means of which suitable indicator and control means may be
adjusted or controlled. In addition FIG. 1 also illustrates a
stationery obstruction Hi which is positioned on the right side of
traffic lane F1.
FIG. 2 primarily illustrates the circuitry associated with the
single detector 1, and as hereafter discussed in greater detail
like circuitry is provided for the remaining detectors.
During each occupancy of the detector 1 by a vehicle, a vehicle
impulse will be produced, which will be conducted to a measuring
device M, and which in turn controls a timing generator ZG. The
latter is operative to produce impulses, for example of 20 m/sec,
and delivers them to a time measuring unit ZM, which may be in the
form of a counter, and will count the number of impulses from
generator ZG, following triggering of the device M by the vehicle,
until another vehicle occupies the detector 1. Upon the receipt of
the new vehicle impulse at the measuring device M, the time
measuring device ZM will be reset, over the timing generator ZG, to
zero and the time total of the counter ZM will be simultaneously
conducted to a mean value forming device MW1.
The signal thus transmitted to the device MW1 represents the time
duration of the interval between two vehicles. To avoid the
possibility of false indication due to long time intervals, a
suitable time control tm may be provided in connection with the
time generator ZG, to provide an impulse after a predetermined time
in the event no vehicle impulses have been received within the
specified time period. The measuring device M, timing generator ZG,
measuring device ZM and timing control tm may collectively be
termed the "measuring system." The respective time intervals,
arriving successively, are averaged in the mean value forming
device MW1 and the results are stored in memories, comprising
respective registers R1 and R2, after the arrival of each new time
interval, for further evaluation.
In this connection, difference-forming means is provided in the
mean value forming device MW1, which will initially form the
difference between the old mean value Za of a time interval and the
new time interval Zn. This difference (Zn - Za) is then multiplied
by a factor .alpha. 1 by means of a product generator associated
with the meanforming device MW1 whereby the mean value Zn at the
output of the latter is equal to Za + .alpha. 1 (Zn - Za), and is
added to the contents of registers R1 and R2 for storage, whereby
the register R1 stores the value Za and the register R2 stores the
value Zn.
Simultaneously, the difference (Zn - Za) is conducted to modifying
means comprising a product-forming device PB1, which is illustrated
as being in the form of a squaring device, whereby there appears at
the output thereof the value (Zn - Za).sup.2 which represents the
difference value Sn. The output of the squaring device PB1 is
supplied to a second mean-forming device MW2 which operates in the
same manner as the device MW1, but as will be apparent from the
circuit, operates with the factor .alpha. 2. The results thereof
are stored in the respective registers R3 and R4, with the register
R3 storing the last or preceeding mean value Sa while the register
R4 stores the new or latest mean value Sn.
The contents of the registers R2 and R4 are supplied to a
product-forming device PB2 operable under the control of a timing
generator TG, which provides an interrogation impulse, for example,
every 60 seconds. As a result, a product a.sub.1 is formed by the
described circuitry from the mean time interval Zn and the mean
time difference Sn for the detector 1, under the control of the
timing generator TG.
The circuitry, thus far described with respect to the detector 1 is
duplicated for each of the other detectors 2-4 whereby similar
products will be produced for each of the other detectors. The
product a.sub.1 from the product-forming device PB2 is conducted to
a quotient-forming device QB, the other input of which receives the
product a.sub.2 from the corresponding product forming device PB2,
associated with the circuit of the detector 2. The quotient values
Kn are supplied to a third mean value forming device MW3, which
device is similarly constructed to the devices MW1 and MW2 and thus
provides a mean value Kn (A) of the quotients Kn of the measuring
values received from the detectors 1 and 2 at each interrogation
impulse from the monitoring location A. The mean value Kn (A) is
conducted to a difference-forming device DB1 and to a register R5,
which is operable to store the previous quotient Ka. In like manner
the mean value Kn (B) of the quotient Kn, derived from the
detectors 3 and 4, at the monitoring location B, will be derived
from a corresponding mean value forming device and associated
circuitry.
It will be appreciated from the above description that the
product-forming device PB2, quotient-forming device QB, means value
forming device MW3 and associated circuitry thus form linking means
for memories R2 and R4 as well as linking means (at a.sub.2 of QB
and Kn(B) at DB1 for detectors 3 and 4 from monitoring location B
with detectors 1 and 2 from monitoring location A.
Thus the detection and measurement of the following magnitudes
involved in the arrangement of FIG. 1 is assured, and may be
illustrated in the following tabulation:
I. Average time gaps:
Z.sub.A1, Z.sub.A2, Z.sub.A3, Z.sub.A4 and therefrom ##EQU1##
II. Variation of the time gaps:
S.sub.A1, S.sub.A2, S.sub.A3, S.sub.A4 and therefrom S ##EQU2## X
and Y, assuming an equal lane division, are to a great extent,
independent from the traffic load and they thus do not depart from
normal range of values with small traffic density fluctuations.
If no obstacle is present, the following will be applicable:
X.sub.A .apprxeq. X.sub.B, Y.sub.A .apprxeq.Y.sub.B
If an obstacle is present in the case illustrated, the following
will be applicable:
Z.sub.B3 > Z.sub.A1 Due to density fluctua- tions caused by lane
Z.sub.B4 < Z.sub.A2 changes X.sub.B >> X.sub.A and
S.sub.B3 > S.sub.A1 Since S.sub.B3 involve free traffic of
fairly small S.sub.B4 > S.sub.A2 density and S.sub.B4 involves
forced traffic of higher density
Y.sub.B >> Y.sub. A
also
X.sub.B . Y.sub.B = K.sub.B >>> X.sub.A . Y.sub.A =
K.sub.A
Thus, the difference of the quotients Kn (A); Kn (B) is formed
every 60 seconds and is supplied to an evaluation system AW. As it
has been explained, this difference thus is an evaluatable
magnitude, representative of the obstructed condition of the
traffic path SA. No obstacle is present in the case of a different
"zero" value, whereby each deviation from the "zero" value serves
as a measure or evaluation of the obstruction.
Additively, a difference of the quotients (Kn - Ka) of a monitoring
location A (or, of course, of other monitoring locations such as B)
can be formed for each individual measuring loctions such as A,
between two or several successive interrogation intervals, for
example, by a second difference forming device DB2, and thus
conclusions may be obtained with respect to the measurement of the
time change of the obstruction. In order to differentiate between
locally fixed and mobile obstructions Hi, the first differences are
taken into account accordingly, with respect to space and location.
As can be described in detail from the following tabulation:
Locally fixed obstructions and moving obstructions
The following is applicable for normal non-obstructed traffic:
K.sub.i,.sub.j .apprxeq. K.sub.i.sub.-1,.sub.j .apprxeq.
K.sub.i,.sub.j.sub.-1 .apprxeq. "constant"
thus
K.sub.i,j - K.sub.i.sub.-1,j .apprxeq. 0 since the quotient K is
independent from density K.sub.i,j - K.sub.i,j.sub.-1 .apprxeq. 0
fluctuations to a great extent, the following is true i: Measuring
cross section j: Time interval
The following is applicable for a locally fixed obstruction:
.vertline.K.sub.i,j - K.sub.i.sub.-1,j .vertline.>> 0
.fwdarw. obstruction
.vertline.K.sub.i,j - K.sub.i,j.sub.-1 .vertline..apprxeq. 0
.fwdarw. Time constancy
The following is applicable for moving obstructions:
.vertline.K.sub.i,j - K.sub.i.sub.-1,j .vertline.> 0 .fwdarw.
obstruction
.vertline.K.sub.i,j - K.sub. 1,j.sub.-1 .vertline.>> 0
.fwdarw. Time change
Diagrams of the frequency distribution H of the time gaps are
illustrated in FIG. 3. The solid line C represents the traffic flow
of a given strength in the normal case, and the dotted line C' the
same traffic flow in the case of an obstruction. It can be seen
from the diagrams that the true characteristic values, namely the
mean value Z (as the mean value of the time interval) and the
variation or dispersion S, (as a measure or evaluation for the
dispersion of the time interval), change substantially according to
the values Z' or S', respectively.
In order to explain these changes, the surfaces F or F',
respectively, were considered with the curves C or C',
respectively, which, according to definition of S or S',
respectively amount to 75% of the entire surfaces of their
associated curve C or C'.
The surfaces F or F' are equally large in the case of an equal
number of observed vehicles. The nature of the shifting of the
surfaces F or F', respectively, is clearly defined by the
magnitudes Z and S or Z' and S', respectively, whereby S or S'
represents the concentration of the surface upon the abscissa.
Finally, the extent of obstruction K upon a highway is illustrated
in FIG. 4, wherein a distinction is made between areas with no
traffic jam (not hatched) and the area where a jam is produced
(cross-hatched). It will be noted therefrom that with the
obstruction K for the area with no jam (not hatched), good
measuring results are achieved with the aboved mentioned system.
If, however, a traffic jam (cross-hatched area) occurs, the
magnitude K will only supply valuable results up to a certain
boundary value > KG. In such case the loop occupation B can be
introduced as an additional criteria, which will enable the
achievement of a continuous supervision for all possible traffic
conditions, including that involving the obstruction K.
Having thus described my invention, it is obvious that although
minor modifications might be suggested by those versed in the art,
it should be understood that I wish to embody within the scope of
the patent warranted hereon all such modifications as reasonably
and properly come within the scope of my contribution to the
art.
* * * * *