U.S. patent number 3,710,312 [Application Number 05/124,599] was granted by the patent office on 1973-01-09 for method and apparatus for controlling traffic flow in accordance with traffic presence.
This patent grant is currently assigned to Gulf & Western Industries, Inc.. Invention is credited to Frank W. Hill.
United States Patent |
3,710,312 |
Hill |
January 9, 1973 |
METHOD AND APPARATUS FOR CONTROLLING TRAFFIC FLOW IN ACCORDANCE
WITH TRAFFIC PRESENCE
Abstract
The presence of traffic in at least one of the intersecting
passageways is monitored by developing a presence signal so long as
a vehicle is present in a predetermined area and the presence
signal is utilized to control the energization of a traffic signal
light so as to initiate termination of a go signal display for
traffic in the passageway which previously had right-of-way.
Traffic presence detectors are provided also within the
intersection itself to prevent yielding right-of-way to traffic in
an intersecting passageway until the vehicle has left the
intersection.
Inventors: |
Hill; Frank W. (Moline,
IL) |
Assignee: |
Gulf & Western Industries,
Inc. (New York, NY)
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Family
ID: |
22415802 |
Appl.
No.: |
05/124,599 |
Filed: |
March 15, 1971 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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870449 |
Oct 23, 1969 |
3602882 |
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563143 |
Jun 6, 1966 |
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Current U.S.
Class: |
340/923 |
Current CPC
Class: |
G08G
1/08 (20130101) |
Current International
Class: |
G08G
1/08 (20060101); G08G 1/07 (20060101); G08g
001/01 () |
Field of
Search: |
;340/31R,38L,37 |
Foreign Patent Documents
Other References
Manual on Uniform Traffic Control Devices for Streets and Highways,
pp. 320-1 U.S. Dept of Commerce, Bureau of Public Roads,
Washington, D.C. June 1961.
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Primary Examiner: Cooper; WIlliam O.
Parent Case Text
This application is a division of co-pending application, Ser. No.
870,449, filed Oct. 23, 1969, now U.S. Pat. No. 3,602,882, which
is, in turn, a continuation of application Ser. No. 563,143 filed
June 6, 1966 now abandoned.
Claims
What is claimed is:
1. In a traffic control system for controlling the operation of
traffic signal means displaying at least go and caution signals to
traffic in each of at least first and second intersecting traffic
lanes each providing for traffic movement in a distinct direction
the improvement comprising:
first and second presence detector means for respectively
monitoring an area in the path of said first lane and an area in
the path of said second lane, said areas being adjacent to the
intersection of said lanes and providing first and second presence
signals so long as traffic is present in said respective areas,
signal control means for controlling said signal means to display a
go signal to traffic in said first lane so long as said second
presence signal is not provided, said signal control means
including circuit means for timing an extended go interval for said
go signal display to traffic in said first lane upon the occurrence
of said second presence signal being provided during a period in
which said first presence signal is provided, said signal control
means comprising a counter means for completing successive output
circuits in response to successive stepping of said counter, one of
said output circuits being operatively connected for actuating a go
signal, one of said output circuits being operatively connected for
energizing a caution signal, said counter being stepped by said
first and second presence signals from said first and second
detector means, means for energizing the first lane caution circuit
in response to termination of the first lane go signal, means for
energizing the second lane caution signal in response to completion
of the second lane go signal, each caution signal energizing means
for a selected lane being arranged to render caution signals in
response to the presence detector means in the traffic lane of said
selected signal.
2. A method of controlling the operation of traffic signal means
displaying go, caution and stop signals to traffic in each of at
least first and second intersecting traffic lanes each providing
for traffic movement in a distinct direction and comprising the
steps of;
energizing said traffic signal means to display a go signal to
traffic in said first lane and a stop signal to traffic in said
second lane;
during said go signal display to traffic in said first lane,
electrically sensing whether traffic is present in a predetermined
area in each of said first and second lanes and providing first and
second presence signals so long as traffic is present in said
respective areas;
forming sequencing signals;
counting such sequencing signals;
producing traffic signal-energizing signals successively in
response to such sequencing signals;
utilizing said first and second presence signals for activating
said traffic signal energizing signals to control the energization
of said traffic signal means so that said go signal is displayed to
traffic in said first lane so long as only said first presence
signal is provided, and then when said second presence signal is
also provided initiating termination of said go signal display to
traffic in said first lane.
3. A method as set forth in claim 2, wherein said step of
initiating termination of said go signal display to traffic in said
first lane includes the step of first electrically timing an
extended go period during which said signal means is energized to
display a go signal to traffic in said first lane and then
energizing said signal means to display only a caution signal to
traffic in said first lane.
4. In a traffic control system for controlling the operation of
traffic signal means displaying traffic commands to traffic in at
least first and second intersecting traffic lanes each providing
for traffic movement in a distinct direction wherein the traffic
commands displayed to traffic in each lane sequentially include at
least one go interval and a caution interval, the improvement
comprising:
solid state traffic interval sequencer means for receiving trigger
signals providing interval signals sequentially and upon receipt of
each said trigger signal allocating a different one of said
intervals to one of said lanes;
first and second presence detector means for respectively
monitoring an area in the path of said first lane and an area in
the path of said second lane, said areas being adjacent to the
intersection of said lanes and providing first and second presence
signals so long as traffic is present in the respective areas;
sequencer control means for applying said trigger signals to said
sequencer means, and including go signal control means for
receiving said first and second presence signals to control said
sequencer means to allocate a go signal interval to said first lane
so long as said first presence signal is provided and said second
presence signal is not provided.
5. In a traffic control system as set forth in claim 4, a
combination wherein said go signal control means includes circuit
means for timing an extended go interval in response to said second
presence signal being provided during the period that said first
presence signal is provided and then providing one of said trigger
signals for application to said sequencer means to allocate said
caution interval to said first lane.
6. In a traffic control system as set forth in claim 4, a
combination wherein said sequencer means includes an input circuit
for receiving said trigger signals and a plurality of output
circuits which are selectively energized in accordance with the
number of trigger pulses applied to said input circuit, said output
circuits adapted to be coupled to said signal means for energizing
said signal means to display traffic commands in dependence upon
which of said output circuits are energized.
7. Traffic control apparatus comprising traffic signal means for
indicating right-of-way to at least two intersecting traffic lanes
each providing for traffic movement in a distinct direction,
respective presence detector means for monitoring areas in the
paths of said lanes, said areas being adjacent to the intersection
of said lanes and for providing respective presence signals in
response to the presence of traffic in said areas, and signal
control means for causing said signal means to indicate
right-of-way to traffic in any first one of said lanes and to deny
right-of-way to traffic in any second one of said lanes, said
signal control means including first responsive means responsive to
a presence signal from said second lane in the absence of a
presence signal from said first lane, and second responsive means
responsive to a presence signal from said second lane in the
presence of a presence signal from said first lane, so that said
signal control means causes the indication given by said signal
means to change substantially immediately, or after a delay, when
said first or second responsive means responds, respectively.
8. A method for controlling the operation of traffic signal means
for displaying alternately go and stop signals to traffic in at
least first and second intersecting traffic lanes each providing
for traffic movement in a distinct direction and comprising the
steps of:
a. energizing said traffic signal means to display a go signal to
traffic in said first lane and a stop signal to traffic in said
second lane;
b. creating a first electrical signal when traffic is present in a
first preselected area of said second lane, said first area being
adjacent the intersection of said first and second traffic
lanes;
c. creating a second electrical signal when traffic is present in a
second preselected area of said first lane, said second area of
said first lane being adjacent the intersection of said first and
second traffic lanes;
d. providing alternative circuit means for creating, upon existence
of said first signal, either a third electrical signal upon
concurrent existence of said first and said second signals or a
fourth electrical signal upon existence of said first signal and
absence of said second signal:
e. terminating said go signal to traffic in said first lane in a
first time upon creation of said fourth signal;
f. alternatively terminating said go signal to traffic in said
first lane in a second time greater than said first time upon
receipt of said third signal; and,
g. giving preference to said alternate termination.
9. A system for controlling the operation of traffic signal means
for displaying alternately go and stop signals to traffic in at
least first and second intersecting traffic lanes each providing
for traffic movement in a distinct direction, said system
comprising:
a. means for energizing said traffic signal means to display a go
signal to traffic in said first lane for a duration and a stop
signal to traffic in said second lane during said duration;
b. means for creating a first electrical signal when traffic is
present in a preselected area of said second lane, said area being
adjacent the intersection of said first and second traffic
lanes;
c. means for creating a second electrical signal when traffic is
present in a preselected area of said first lane, said area of said
first lane being adjacent the intersection of said first and second
traffic lanes;
d. means for extending the duration of said display of said go
signal to traffic in said first traffic lane; and,
e. means responsive to the concurrent existence of said first and
second signals for causing operation of said extension means.
10. A system for controlling the operation of traffic signal means
for displaying alternately go and stop signals to traffic in at
least first and second intersecting traffic lanes each providing
for traffic movement in a distinct direction, said system
comprising:
a. means for energizing said traffic signal means to display a go
signal to traffic in said first lane for a duration and a stop
signal to traffic in said second lane during said duration;
b. means for creating a first electrical signal when traffic is
present in a preselected area of said second lane, said area being
adjacent the intersection of said first and second traffic
lanes;
c. means for creating a second electrical signal when traffic is
present in a preselected area of said first lane, said area of said
first lane being adjacent the intersection of said first and second
traffic lanes;
d. means for maintaining said go signal displayed to traffic in
said first lane until said first signal is created;
e. first termination means for terminating said go signal display
to traffic in said first lane upon creation of said first
signal;
f. means for blocking operation of said first terminating means
upon concurrent existence of said first and second signal;
g. second means for terminating said go signal displayed to traffic
in said first traffic lane upon concurrent existence of said first
and second signals, and
h. said second termination means including a timing device for
extending the time of termination of said go signal displayed to
traffic in said first lane by a preselected amount.
11. A system for controlling the operation of traffic signal means
for displaying alternately go and stop signals to traffic in at
least first and second traffic lanes each providing for traffic
movement in a distinct direction, said lanes intersecting at an
intersection area including both of said lanes, said system
comprising:
a. means for cycling said signal means between a first cycle
portion having a first given time length and displaying a go signal
to traffic in said first lane and a stop signal to traffic in said
second lane and a second cycle portion having a second given time
length and displaying a stop signal to traffic in said first lane
and a go signal to traffic in said second lane;
b. means for creating a third cycle portion between said first and
second cycle portions with a stop signal displayed to traffic in
both said first and second traffic lanes;
c. a presence detector means for creating an electrical signal when
a vehicle is in said intersection area;
d. means for terminating said first portion of said cycle;
e. means responsive to termination of said first portion of said
cycle and responsive to said electrical signal for energizing said
third cycle creating means;
f. means for maintaining said third cycle means energized for the
duration of said electrical signal; and,
g. means for initiating said second cycle portion when said
electrical signal ceases.
12. A traffic control device for controlling the operation of
traffic signal means for displaying go and stop signals to traffic
in at least first and second traffic lanes each providing for
traffic movement in a distinct direction, said lanes intersecting
at an intersection area including both of said lanes, said device
comprising:
a. first detecting means for detecting the presence of traffic in a
first preselected area, said area being adjacent said intersection
area;
b. second detecting means for detecting the presence of traffic in
a second preselected area, said second preselected area being
adjacent said intersection area;
c. sequencing means having a first output for initiating a first
cycle portion when a go signal is displayed to traffic in said
first traffic lane and a stop signal is displayed to traffic in
said second traffic lane, second output means for initiating a
second cycle portion with a stop signal displayed to traffic in
said first traffic lane and a go signal displayed to traffic in
said first traffic lane and means for shifting between said first
and second output means;
d. stepping means responsive to said first and second detecting
means for causing said sequencing means to shift between said first
and second outputs;
e. means for sensing the concurrent detection of traffic by both
said first and second detecting means; and,
f. means for extending said first cycle portion in response to said
sensing means and independent of said second cycle portion.
13. A device as defined in claim 12 wherein said sequencing means
is a binary counter.
14. A device as defined in claim 12 including:
g. means for creating a third cycle portion between said first and
second cycle portions, said third portion displaying a stop signal
to traffic in both of said lanes;
h. third detecting means for detecting the presence of traffic in
said intersection area;
i. means responsive to said third detecting means for initiating
said third cycle creating means upon energization of said stepping
means; and,
j. means independent of said first and second cycle portions for
maintaining said third cycle until all traffic leaves said
intersecting area.
15. In a traffic control system for controlling operation of
traffic signal means displaying go and stop signals to traffic in
first and second traffic lanes each providing for traffic movement
in a distinct direction, said lanes intersecting at an intersection
area, the improvement comprising:
a. all red clearance control means for controlling the said signal
means to display simultaneously a stop signal to traffic in both of
said lanes; and,
b. said all red clearance control means including first circuit
means adapted to be coupled to presence detector means located in
said intersection area for providing an all red presence signal so
long as traffic is present in said area, and second circuit means
for maintaining said stop signals displayed to both of said lanes
so long as said all red presence signal is developed by said
presence detector means.
16. In a traffic control system for controlling operation of
traffic signal means displaying at least go, stop and caution
signals to traffic in first and second traffic lanes each providing
for traffic movement in a distinct direction, each lane
intersecting at an intersection area, the improvement
comprising:
a. caution signal control means for controlling the time duration
of operation of said caution signal displayed to traffic in each
phase;
b. said caution control means including a first presence detector
means in the first of said lanes and in said intersection area for
generating a first signal when a vehicle is in said first lane and
in said intersection area and a second presence detector in said
second lane and in said intersection area for generating a second
signal when a vehicle is in said second lane and in said
intersection area;
c. first control means responsive to said first signal for
controlling the length of time said caution signal displayed to
traffic in said first lane is on; and,
d. second control means responsive to said second signal for
controlling the length of time said caution signal displayed to
traffic in said second lane is on.
17. A system for controlling the operation of traffic signal means
for displaying alternately go and stop signals to traffic in at
least first and second intersecting traffic lanes each providing
for traffic movement in a distinct direction, said system
comprising:
a. means for energizing said traffic signal means to display a go
signal to traffic in said first lane for a duration and a stop
signal to traffic in said second lane during said duration;
b. means for creating a first electrical signal when traffic is
present in a preselected area of said second lane, said area being
adjacent the intersection of said first and second traffic
lanes;
c. means for creating a second electrical signal when traffic is
absent from said preselected area;
d. means for creating a third electrical signal when traffic is
present in a preselected area of said first lane, said area of said
first lane being adjacent the intersection of said first and second
lanes;
e. means for creating a fourth electrical signal when traffic is
absent from said area of said first lane;
f. means for extending the duration of the display of a go signal
to traffic in said first lane;
g. first sensing means for sensing the concurrent existence of said
first and third electrical signals;
h. means responsive to said first sensing means for causing
operation of said duration extending means;
i. second sensing means for sensing the existence of said first and
fourth electrical signals; and,
j. means responsive to said second sensing means for blocking
operation of said duration extending means.
Description
This invention relates to the art of traffic control and, more
particularly, to method and apparatus for controlling traffic flow
through an intersection of at least two traffic phases in
accordance with the presence of traffic in the phases.
Traffic control methods known heretofore for controlling traffic
flow through an intersection of at least two traffic phases based
on traffic demand, as opposed to a pretimed basis, require for
practice the use of an actuated controller designed around spot
detectors, such as the familiar treadle pad located on a roadbed.
In such a control method, a vehicle approaching an intersection,
through which it is denied right-of-way by a stop signal displayed
by a traffic signal light, must pass over and momentarily actuate a
spot detector in order to register its demand for right-of-way
movement with an actuated intersection controller controlling the
signal displays of the traffic signal light. The actuated
controller, such as a semi-actuated or full-actuated controller,
must include memory circuitry for remembering the momentary
actuation of the spot detector until the controller actually
allocates a right-of-way signal to the vehicle demanding
right-of-way movement. However, at the instant in time at the
controller actually commences allocation of a right-of-way signal
to the vehicle, the vehicle may have "disappeared" and no longer
requires right-of-way movement through the intersection. That is,
for example, a single vehicle might pass over and actuate a cross
street spot detector and then park before reaching the stop line at
the intersection of the cross street and a main street, or enter a
gasoline station before reaching the stop line, or the vehicle may
have entered the intersection and turned right on the main street,
as is permitted in some states (such as California, where many
intersections have posted signs reading RIGHT TURN PERMITTED ON RED
AFTER STOP). Accordingly, an allocation of a cross street
right-of-way signal to the "disappeared" vehicle constitutes an
unnecessary waste of right-of-way time, which must be taken away
from the main street traffic flow.
A further problem with such previous traffic control methods is
that of the "appearing vehicle". That is, for example, a vehicle
may enter a cross street from a gasoline station, or parking lot,
between a cross street spot detector and the stop line at the
intersection of the cross street and a main street. Since the cross
street spot detector has not been actuated, the vehicle is denied
right-of-way movement until the vehicle is backed up to actuate the
spot detector to register its demand for right-of-way movement
through the intersection with the intersection controller.
A still further problem with such a traffic control method is that
of "slow vehicle start". That is, for example, when a roadway
pavement ices over during severe winter conditions, vehicles
normally require a longer period of time to start moving and clear
an intersection. This period of time may be referred to as the
vehicle initial or minimum period of time, and is normally a fixed
period of time controlled by the local intersection controller for
permitting a given number of vehicles to commence movement through
an intersection, and is not sufficient to permit that given number
of vehicles to clear the intersection during adverse winter
conditions when the pavement ices over. This problem is partially
solved on a temporary basis during such adverse winter conditions
by maintenance men going to the intersection controller and
resetting the vehicle initial time so that it times a longer period
of time. The vehicle initial period is only one of many time
periods that are timed by an intersection controller during each
traffic signal cycle and, accordingly, by increasing this time
period there results an inefficiency in the operation of the
controller for the remaining periods of time to be timed during
each traffic signal cycle.
In addition to the foregoing problems, traffic actuated controllers
known heretofore for practicing such previous traffic control
methods are, of necessity, quite complex. More particularly,
whereas the vehicle initial time period discussed above is
frequently a fixed, manually adjusted interval of time set on an
intersection controller, many controllers allocate a variable
initial period of time. A variable initial period of time, for
example, is dependent on the number of vehicles which have actuated
a spot detector. Accordingly, an intersection controller for
allocating a variable initial period of time must include circuitry
for counting the number of vehicles which actuated a spot detector
and converting the count to a time period which is variable in
accordance with the number of registered vehicle actuations. Many
controllers also include circuitry for allocating vehicle extension
periods in accordance with vehicle actuations of a spot detector.
Still further, many controllers are further complicated by the
inclusion of circuitry for placing a recall signal when a maximum
vehicle interval has been timed out before all of the spot detected
vehicles had a theoretical opportunity to enter the intersection so
that they may be allocated a right-of-way interval during the next
traffic signal cycle.
Further, many municipalities require that an all red clearance
interval be allocated to all traffic phases, or movements, at an
intersection controlled by a traffic controller each time one of
the phases is giving up right-of-way movement and another phase is
about to be given right-of-way movement. One reason for an all red
clearance interval is to insure that an intersection is clear
before a traffic phase is given right-of-way movement, thereby
avoiding accidents due to vehicles "jumping the light." Traffic
controllers known heretofore for practicing methods of traffic
control for allocating an all red clearance interval, allocate a
fixed time interval for the all red clearance based on traffic
studies, as opposed to the actual conditions prevailing at the
controlled intersection. Thus, in the event that no vehicles are
present in the controlled intersection, the time allotted for the
all red clearance interval is wasted time during the traffic signal
cycle.
Most municipalities require that a yellow clearance signal be
displayed to a traffic movement between the go signal and the stop
signal displayed to that movement. The yellow clearance signal is
displayed while the other movements controlled by the intersection
controller are denied right-of-way movement by a stop signal. Thus,
the yellow clearance signal serves as a safety interval to allow
vehicles arriving late in the intersection to clear the
intersection before the next movement receives a go signal. The
yellow signal is allocated by the intersection controller on a
fixed timed basis, as opposed to the actual traffic conditions
prevailing at the controlled intersection. Thus, if no vehicles are
present at the intersection, the time allocated to the yellow
clearance signal is wasted time during the traffic signal
cycle.
The present invention is directed toward a new method and apparatus
for its practice of controlling traffic flow through an
intersection of at least two traffic phases based on whether a
vehicle is actually present within a particular area in at least
one of the movements approaching an intersection and/or within the
intersection itself, whereby the noted disadvantages, and others,
of previous traffic control methods and apparatuses for their
practice are overcome.
In accordance with the invention, the new traffic control method
and apparatus for its practice provide for monitoring a
predetermined area in the path of at least one traffic phase for
the presence of traffic; developing a presence signal so long as a
vehicle is present in the predetermined area; and, utilizing the
presence signal to control the energization of a traffic signal
light so as to initiate termination of a go signal display to the
phase having right-of-way.
In accordance with another aspect of the present invention, the
presence signal is utilized to energize a timing means for timing a
predetermined period of time and then developing a termination a
termination signal, which is utilized for energizing the traffic
signal means in such a manner to terminate a go display to the
movement having right-of-way and commence display of a caution
signal to that movement.
In accordance with a still further aspect of the present invention,
a predetermined area located at the intersection of the movements
is monitored for the presence of traffic, and a caution signal is
developed so long as a vehicle is present in the intersection area
with the caution signal being utilized to control the time duration
that the traffic signal means displays a caution signal to the
movement previously having right-of-way.
In accordance with a still further aspect of the present invention,
an all red clearance signal is developed so long as a vehicle is
present in the intersection area, with the all red clearance signal
being utilized to control the time duration that the traffic signal
means displays a stop signal to all of the traffic movements.
The primary object of the present invention is to provide method,
and apparatus for its practice, for efficiently controlling traffic
flow based on whether vehicles are actually present in the
approaches to an intersection.
Another object of the present invention is to provide a method of
traffic control wherein the problem of the disappearing vehicle is
solved.
A still further object of the present invention is to provide a
method of traffic control wherein the problem of an appearing
vehicle is solved.
In accordance with a still further object of the present invention,
a method of traffic control is provided wherein the problem of
"slow vehicle start" is solved.
A still further object of the present invention is to provide a
method wherein the apparatus for its practice need not include
memory circuitry.
A still further object of the present invention is to provide a
method of traffic control wherein apparatus for its practice need
not include variable initial interval circuitry.
A still further object of the present invention is to provide a
method of traffic control wherein the apparatus for its practice
need not include circuitry for allocating vehicle extensions in
accordance with traffic actuations registered with a spot
detector.
In accordance with a still further object of the present invention,
a method of traffic control is provided wherein the apparatus for
its practice need not include circuitry for placing a recall signal
when a maximum interval has timed out before all of the registered
vehicles have had an opportunity to clear the intersection.
In accordance with a still further object of the present invention,
there is provided a method and apparatus for its practice for
controlling the time duration of a caution signal displayed by an
intersection traffic signal light in accordance with whether
vehicles are actually present in the intersection.
In accordance with a still further object of the present invention,
method and apparatus for its practice are provided for controlling
the time duration of an all red clearance signal displayed by an
intersection traffic signal light in accordance with whether
vehicles are actually present in the intersection.
The method of traffic control, in accordance with the invention,
may incorporate various procedural steps of which the preferred
procedures will be described in detail in the specification and
illustrated in the accompanying drawings, which are a part hereof.
Further, the invention may be practiced with various substantially
different apparatuses of which two will be described in detail in
the specification and illustrated in the accompanying drawings,
which are a part hereof and wherein:
FIG. 1 is a plan view illustrating a typical intersection of two
traffic phases to which the present invention may be applied;
FIG. 2 is a graphical illustration of the preferred procedure for
practicing a method in accordance with the present invention for
controlling traffic flow through the intersection illustrated in
FIG. 1;
FIG. 3 is a schematic block diagram illustration of an apparatus
for practicing the method illustrated in FIG. 2;
FIG. 4 is a plan view illustrating a typical intersection of two
traffic phases to which a second aspect of the method in accordance
with the invention may be applied;
FIG. 5 is a graphical illustration of the procedure for practicing
the second aspect of the method in accordance with the invention
for controlling traffic flow through the intersection illustrated
in FIG. 4;
FIG. 6 is a schematic block diagram illustration of an apparatus
for practicing the method illustrated in FIG. 5; and,
FIG. 7 is a graphical illustration of traffic intervals versus
operating circuits with respect to the circuits illustrated in
FIGS. 3 and 6.
Referring now to the drawings wherein the showings are for the
purposes of explaining the preferred method of traffic control and
apparatus for its practice, and not for purposes of limiting same,
there is illustrated in FIG. 1 a typical intersection of two
traffic phases, or movements, phase A and phase B. Adjacent the
intersection of the two phases there is schematically illustrated
stop lines SL which may be located as desired by a municipal
traffic engineer. At each approach to the intersection there is
provided a presence detector, i.e., detectors D1 and D2 for the
approaches of phase A and detectors D3 and D4 for the approaches of
phase B. Detectors D1, D2, D3 and D4 are illustrated as loop
detectors, which are well known in the art of traffic control, and
generally comprise a closed wire loop embedded in a roadway, with
the loop configuration defining an area under surveillance by the
detector, which together with associated circuitry develops an
output signal so long as a vehicle is present within the area under
surveillance. Alternatively, detectors D1, D2, D3 and D4 may take
the form of other presence detectors such as overhead mounted
ultrasonic detectors which, in a manner similar to that of loop
detectors, serve to monitor, or survey, a predetermined area on a
roadbed for the presence of vehicles, and provide an output signal
so long as a vehicle is present in the area under surveillance. As
shown in FIG. 1, each loop detector extends from a point
substantially adjacent the stop line SL for the associated
approach, and away from the intersection for a distance sufficient
to detect the presence of a number of vehicles pursuant to a
traffic engineer's schedule. The width of the loop detector should
be sufficient to detect the presence of vehicles on as many lanes
that are approaching the intersection along that particular phase.
The loop detectors for each phase are connected together to a local
traffic controller LC-1, which controls the operation of an
intersection traffic signal S-1 which displays go, caution and stop
signals to phases A and B. In addition to loop detectors D1, D2, D3
and D4 an all red clearance loop detector D5 is illustrated in FIG.
1. Loop detector D5 has a configuration so that it serves to detect
the presence of vehicles within the intersection area bordered by
stop lines SL at the approaches to the intersection.
Referring now to FIG. 2, there is shown a graphical illustration of
a preferred procedure of practicing a method, in accordance with
the invention, for controlling traffic flow through the
intersection illustrated in FIG. 1. The following description given
with respect to FIG. 2 sets forth two procedural variations,
Procedure I and Procedure II. Thereafter, a description of
apparatus for practicing the method is given with respect to the
circuit illustrated in FIG. 3.
Briefly, the method in accordance with the invention for
controlling traffic flow through the intersection of phases A and
B, illustrated in FIG. 1, comprises the steps of: providing a
traffic signal light S-1 for displaying go, caution and stop
signals to traffic phases A and B; energizing traffic signal S-1 to
display a go signal to phase A and a stop signal to phase B;
providing traffic monitoring means in the form of loop detectors D1
and D2 for phase A and D3 and D4 for phase B for respectively
developing a phase A presence signal and a phase B presence signal
so long as a vehicle is present in the areas of influence of these
detectors; and, utilizing the phase B presence signal for
controlling energization of traffic signal S-1 to initiate
termination of the go signal display to phase A. More particularly,
the procedural steps, in accordance with the invention, for
controlling the traffic flow through the intersection illustrated
in FIG. 1 are set forth below with respect to Procedure I and a
modified version thereof, Procedure II.
PROCEDURE I
This procedure is given with respect to the graphical illustration
shown in FIG. 2, wherein the steps include:
STEP 1. Energize the traffic signal S-1 to display a go signal to
phase A and a stop signal to phase B.
STEP 2. Monitor phases A and B by means of loop detectors D1, D2,
D3 and D4 for vehicles present within the respective areas of
influence of the detectors.
STEP 3. Recognize the presence of a vehicle in the detector zones
of influence for phase A and phase B, and develop a phase A
presence signal so long as a vehicle is present in the area of
influence of detector D1 or D2, and develop a phase B presence
signal so long as a vehicle is present in the area of influence of
detector D3 or D4.
STEP 4. If in STEP 3 a phase B presence signal is developed and a
phase A presence signal is not developed, then
Step 4a. utilize the phase B signal for energizing traffic signal
S-1 to terminate the phase A go signal display.
STEP 4 (alternative). If in STEP 3 both phase A and phase B
presence signals are developed, then
Step 4b,1. utilize the presence signals to energize a phase A go
signal extension limit timer which serves to time a predetermined
period of time and then develop a phase A go termination
signal.
Step 4b,2. Utilize the phase A go termination signal to energize
traffic signal S-1 to terminate the phase A go signal display.
STEP 5a,1. Energize traffic signal S-1 to display a caution signal
to phase A and energize a phase A caution timer which serves to
time a predetermined caution interval and then develop a phase A
caution termination signal.
STEP 5a,2. Utilize the phase A caution termination signal to
energize traffic signal S-1 to terminate the phase A caution signal
display.
The method steps for the control of phase B traffic flow are
identical with that with respect to STEPS 1 through 5a,2 just
described relative to phase A traffic flow. Accordingly, these
steps should be repeated for phase B traffic flow as indicated by
the like character references and legend shown in FIG. 2 with
respect to both phase A and phase B.
PROCEDURE II
Procedure II is a modification of Procedure I, just described, to
the extent that it includes consideration as to whether vehicles
are present within the intersection area of phases A and B
illustrated in FIG. 1. Briefly, during this procedure, loop
detector D5 is utilized for detecting the presence of a vehicle
within the intersection area for purposes of energizing the traffic
signal S-1 to display stop signals to both phases A and B, i.e., an
all red clearance signal, so long as a vehicle is present.
Accordingly, Procedure II includes STEPS 1 through 5a,2 of
Procedure I together with the following steps:
STEP 6. Monitor the intersection area of phases A and B for the
presence of a vehicle with the zone of influence of loop detector
D5.
STEP 7. Recognize the presence of a vehicle in the zone of
influence of loop detector D5, and develop an all red clearance
presence signal so long as a vehicle remains in the area of
influence of detector D5.
STEP 8. Utilize the all red clearance presence signal to energize
traffic signal S-1 to display a stop signal to both phases A and B,
i.e., an all red clearance signal, so long as the all red clearance
presence signal is developed.
APPARATUS FOR PRACTICING PROCEDURES I AND II
Referring now to FIG. 3, there is schematically illustrated in
block diagram form an apparatus taking the form of a two phase,
full actuated, presence detector traffic controller LC-1 for
practicing Procedures I and II, described hereinabove. It is
contemplated that the controller be constructed so that its control
and switching functions are accomplished with the use of relays; or
a combination of relays and a step switch mechanism; or a
combination of relays and a standard cam switching device; or a
combination of relays and solid state, logic circuitry; or solid
state, logic element circuitry which may include matrix systems for
accomplishing various switching functions. It is also contemplated
that the controller be so constructed that its timing functions are
accomplished by means of thermionic tubes; or thyratron tubes; or
mechanical timers, or solid state timers.
The local controller LC-1, illustrated in FIG. 3, takes the form of
a solid state, logic element controller including a binary counter
BC having a single input circuit, and three output circuits
connected to a binary to decimal converter BDC having output
circuits Nos. 1, 2, 3, 4, 5 and 6; a phase A go signal control
circuit C connected with output circuit No. 1; a phase B go signal
control circuit D connected with output circuit No. 4; a phase A
caution signal control circuit E connected with output circuit No.
2; a phase B caution signal control circuit F connected with output
circuit No. 5; a phase A all red clearance control circuit G
connected with output circuit No. 3; and, a phase B all red
clearance control circuit H connected with output circuit No.
6.
As will become evident from the description that follows, each
control circuit C and D includes two AND circuits, a NOT circuit; a
MULTIPLIER circuit, a PULSE circuit and a TIMER circuit; each
control circuit E and F includes a MULTIPLIER circuit and a TIMER
circuit; and, each control circuit G and H includes a NOT circuit,
a MULTIPLIER circuit and a PULSE circuit. To facilitate the
understanding of this invention, each of these circuits is briefly
explained below.
AND circuit. This is a static element circuit having two or more
input circuits and one output circuit. A positive potential output
signal, known as a (1) signal, is present at its output circuit so
long as all of its input circuits receive a (1) signal. If a ground
potential signal, known as a (0) signal, is present at any of its
input circuits a (0) signal is present at its output circuit.
TIMER circuit. This is a static element timing circuit having an
input circuit and an output circuit. An (1) output signal pulse is
present at its output circuit a predetermined period of time after
an (1) input signal is received at its input circuit.
MULTIPLIER circuit. This is a static element circuit having an
input circuit and two or more output circuits. A (1) signal is
present on each of the output circuits so long as a (1) signal is
present at its input circuit.
PULSE circuit. This is a static element pulse circuit having an
input circuit and an output circuit. An (1) output signal pulse
appears on its output circuit in response to application of an (1)
input signal to its input circuit.
NOT circuit. This is a static element circuit having two input
circuits x and y and an output circuit. A (1) signal is present at
its output circuit so long as a (1) signal is present at its input
circuit y and a (1) signal is not present at its input circuit x.
If a (1) signal is present at its input circuit x, or a (0) signal
is present at its input circuit y, a (0) signal is present at its
output circuit.
Binary counter BC has a single input circuit and three output
circuits, and is capable of counting to seven in response to signal
pulses received at its input circuit. Counter BC may, for example,
take the form of the binary counter illustrated in FIG. 5.9 of
General Electric's Transistor Manual, Seventh Edition. The binary
to decimal converter BDC is connected to the three binary output
circuits of counter BC, and serves to route selected combinations
of the binary outputs to converter output circuit Nos. 1, 2, 3, 4,
5 and 6. Converter BDC, for example, may take the form of a diode
matrix, similar to that as illustrated in FIG. 3 of U.S. Pat. No.
3,435,413, granted Mar. 25, 1969 on application, Ser. No. 462,028,
filed June 7, 1965, assigned to the assignee of the present
invention. The output signals present at converter BDC output
circuit Nos. 1 through 6 take the form of either a (1) signal or a
(0) signal.
GO CONTROL CIRCUITS
The internal circuitry of phase A go control circuit C and phase B
go control circuit D are substantially identical, and, accordingly,
only control circuit C will be described hereinafter in detail,
like components in both circuits being identified in FIG. 3 with
like reference characters. Go control circuit C includes a
MULTIPLIER circuit 10 having a single input circuit connected to
converter BDC output circuit No. 1. MULTIPLIER circuit 10 has three
output circuits respectively connected to a phase A go signal light
12A, to an input circuit of an AND circuit 14, and to an input
circuit of a second AND circuit 16. AND circuits 14 and 16 each
have a second input circuit connected to the output circuit of a
phase B presence signal generator 18B which, in turn, has its input
circuit connected to phase B loop detectors D3, D4. The output
circuit of AND circuit 14 is connected to the input circuit of a
TIMER circuit 20 which, in turn, has its output circuit connected
to the input circuit of binary counter BC. TIMER circuit 20 may,
for example, take the form of a time adjustable unijunction
transistor, RC relaxation oscillator timing circuit which upon
receipt of a (1) signal at its input circuit times a predetermined
period of time and then develops a (1) signal pulse for application
to the input circuit of binary counter BC. AND circuit 16 has its
output circuit connected to a y input circuit of a NOT circuit 22.
The x input circuit of NOT circuit 22 is connected to the output
circuit of a phase A presence signal generator 18a which, in turn,
has its input circuit connected to phase A loop detectors D1, D2.
The output circuit of NOT circuit 22 is connected to the input
circuit of a PULSE circuit 24, which, in turn, has its output
circuit connected to the input circuit of binary counter BC.
CAUTION CONTROL CIRCUITS
The internal circuitry of phase A caution control circuit E and
phase B caution control circuit F are substantially identical and,
accordingly, only caution control circuit E will be described
hereinafter in detail, like components in both circuits E and F
being identified in FIG. 3 with like reference characters. Circuit
E includes a MULTIPLIER circuit 26 having an input circuit
connected with converter BDC output circuit No. 2. MULTIPLIER
circuit 26 also includes two output circuits respectively connected
with a phase A caution signal light 28A, and to the input circuit
of a TIMER circuit 30. TIMER circuit 30 is preferably constructed
in a manner similar to that as described hereinabove with respect
to TIMER circuit 20, and includes an output circuit connected to
the input circuit of binary counter BC.
ALL RED CLEARANCE CONTROL CIRCUITS
The internal circuitry of phase A all red clearance control circuit
G and phase B all red clearance control circuit H are substantially
identical and, accordingly, only control circuit G will be
described hereinafter in detail, like components in both circuits
being identified in FIG. 3 with like reference characters. Circuit
G includes a MULTIPLIER circuit 32 having its input circuit
connected to converter BDC output circuit No. 3, and a first output
circuit connected to an all red clearance signal light 34 for, when
energized, displaying a stop signal to both phase A and phase B.
MULTIPLIER circuit 32 has a second output circuit connected to
input circuit y of a NOT circuit 36. The x input circuit of NOT
circuit 36 is connected to an output circuit of an all red
clearance detector presence signal generator 38 which, in turn, has
its input circuit connected to the all red clearance loop detector
D5. The output circuit of NOT circuit 36 is connected to the input
circuit of a PULSE circuit 40 which, in turn, has its output
circuit connected to the input circuit of binary counter BC .
OPERATION
During each cycle of operation of the presence detector local
controller LC-1, each binary to decimal converter BDC output
circuit, Nos. 1, 2, 3, 4, 5 and 6, is completed once, during which
a (1) signal is present thereon, in response to a (1) signal pulse
applied to the input circuit of binary counter BC. During the time
period that one of the converter BDC output circuits is completed,
the controller allocates at least one traffic interval. Thus, as
shown in the chart illustrated in FIG. 7, traffic interval Nos. 1
and 2 are successively allocated during the time period that
circuit No. 1 is completed; traffic interval No. 3 is allocated
during the time period that circuit No. 2 is completed; traffic
interval No. 4 is allocated during the time period that circuit No.
3 is completed; traffic interval Nos. 5 and 6 are successively
allocated during the time period that circuit No. 4 is completed;
traffic interval No. 7 is allocated during the period that circuit
No. 5 is completed; and, traffic interval No. 8 is allocated during
the time period that circuit No. 6 is completed. Interval Nos. 1
and 5 are respectively the phase A go dwell interval and the phase
B go dwell interval. Interval Nos. 2 and 6 are respectively the
phase A go extension interval and the phase B go extension
interval. Interval Nos. 3 and 7 are respectively the phase A
caution interval and the phase B caution interval. Interval Nos. 4
and 8 are all red clearance intervals. It is to be understood that
during phase A go interval No. 1 the local controller LC-1
allocates a stop interval to phase B and, similarly, during the
phase B go interval No. 5 the local controller LC-1 allocates a
stop interval to phase A, as is common in the art of traffic
control.
A cycle of operation commences upon application of a (1) signal
pulse to the input circuit of binary counter BC, advancing the
local controller LC-1 to interval No. 1, during which a (1) signal
is present on converter BDC output circuit No. 1. This energizes
the phase A go signal light 12A of signal S-1 (FIG. 1), through
MULTIPLIER circuit 10 and applies a (1) signal to one of the input
circuits of each of the AND circuits 14 and 16. Local controller
LC-1 dwells in interval No. 1 allocating a go signal to phase A
until a vehicle enters the area of surveillance of either of phase
B loop detectors D3 or D4.
If a vehicle is not present in the area of influence of phase A
loop detectors D1, D2, a (1) signal is not present at the x input
circuit of NOT circuit 22. During this condition of NOT circuit 22,
when a vehicle is present in the area of influence of either phase
B loop detectors D3 or D4, a (1) signal is applied from the output
circuit of phase B presence signal generator 18B to the second
input circuit of AND circuit 16. Thus, a (1) signal is now present
on the output circuit of AND circuit 16, which is applied to the y
input circuit of NOT circuit 22, and since there is not a (1)
signal applied to the x input circuit, a (1) signal is now present
on the output circuit of NOT circuit 22. This (1) signal is applied
to the input circuit of PULSE circuit 24 which converts the signal
to a (1) signal pulse for application to the input circuit of
binary counter BC. This advances controller LC-1 to de-energize
converter output circuit No. 1 and, hence, de-energize phase A go
light 12A and energize converter circuit No. 2. It will be noted
with respect to the description above, that traffic interval No. 2,
i.e., the phase A go extension interval, was skilled and the
controller advanced directly from interval No. 1 to interval No.
3.
If a vehicle is present in the area of influence of either of the
phase A loop detectors D1 or D2, and either of the phase B loop
detectors D3 or D4, a (1) signal is applied to both the x input
circuit and y input circuit of NOT circuit 22. Accordingly, a (1)
signal will not be present on the output circuit of NOT circuit 22.
However, a (1) signal is now applied to both input circuits of AND
circuit 14. Thus, a (1) signal is applied to the input circuit of
TIMER circuit 20. This causes TIMER circuit 20 to time a
predetermined period of time, which may be termed as the phase A go
signal extension interval No. 2 (FIG. 7), and then develop a (1)
signal pulse which appears at its output circuit. This (1b) signal
pulse may be termed as a phase A go extension termination signal,
and is applied to the input circuit of binary counter BC. This
advances the local controller LC-1 to energize converter output
circuit No. 2 and de-energize converter output circuit No. 1 and,
hence, de-energize phase A go light 12A.
With converter output circuit No. 2 energized, a (1) signal is
applied to MULTIPLIER circuit 26 in control circuit E to energize a
phase A caution signal light 28A of traffic signal S-1 (FIG. 1). A
(1) signal is applied from the output circuit of MULTIPLIER circuit
26 to the input circuit of TIMER circuit 30. This causes the TIMER
circuit 30 to time a predetermined period of time which may be
termed as the phase A caution interval No. 3 (FIG. 7), and then
develop an (1) output signal pulse at its output circuit. This
signal pulse may be termed as the phase A caution interval
termination signal, and is applied to the input circuit of binary
counter BC. This advances controller LC-1 to de-energize converter
output circuit No. 2 and, hence, de-energize phase A caution signal
light 28A, and energize converter output circuit No. 3.
With converter BDC output circuit No. 3 energized, a (1) signal is
applied through MULTIPLIER circuit 32 to energize the all red
clearance light 34 of traffic signal S-1 (FIG. 1), for displaying a
stop signal to both phase A and phase B. A (1 ) signal is also
applied through MULTIPLIER circuit 32 to the y input circuit of NOT
circuit 36. So long as a vehicle is present in the area of
influence of all red clearance detector D5 (FIG. 1) a (1) signal is
applied to the x input circuit of NOT circuit 36 and, accordingly,
a (1) signal is not present on the output circuit of NOT circuit
36. The all red clearance light 34 will remain energized until no
vehicle is present in the area of influence of all red clearance
detector D5. At that time, a (1) signal will not be present at the
x input circuit of NOT circuit 36 and since a (1) signal is present
on its y input circuit, a (1) signal appears on the output circuit
of NOT circuit 36. This signal is converted to a (1) signal pulse
by PULSE circuit 40 and applied to the input circuit of binary
counter BC to advance controller LC-1 so that converter output
circuit No. 3 is de-energized and, hence, all red clearance light
34 is de-energized, and converter output circuit No. 4 is
energized.
The operation of the controller during phase B traffic interval
Nos. 5, 6, 7 and 8 with respect to converter BDC output circuit
Nos. 4, 5 and 6 is identical to that just described for the
operation during phase A traffic interval Nos. 1, 2, 3 and 4 with
respect to converter BDC output circuit Nos. 1, 2 and 3. Thus, no
further description of the operation of local controller LC-1 is
deemed necessary for a complete understanding of the operation of
the controller.
A SECOND ASPECT OF THE INVENTION
Referring now to FIGS. 4, 5 and 6, there is illustrated method and
apparatus for its practice in accordance with a second aspect of
the invention. This aspect of the invention is quite similar to
that as set forth with respect to FIGS. 1 through 3 and,
accordingly, like character references and like legend are used in
FIGS. 4, 5 and 6 for identifying like procedural steps and
components. In FIG. 4 there is illustrated a typical intersection
of two traffic phases, phase A and phase B. Adjacent the
intersection of the two phases there is schematically illustrated
stop lines SL which may be located as desired by a municipal
traffic engineer. At each approach to the intersection there is
provided a presence detector, i.e., detectors D1, D2 for the
approaches of phase A, and detectors D3, D4 for the approaches of
phase B. Detectors D1, D2, D3 and D4 are illustrated as loop
detectors and may, if desired, take the form of ultrasonic
detectors as previously discussed with reference to FIG. 1. The
loop detectors for each phase are connected together to a traffic
controller LC-2 which controls the operation of an intersection
traffic signal S-2, similar to signal S-1 illustrated in FIG. 1,
which displays go, caution and stop signals to phases A and B. In
addition to loop detectors D1, D2, D3 and D4 there is provided an
all red clearance loop detector D5 having a configuration similar
to that as illustrated in FIG. 1, i.e., it serves to detect the
presence of vehicles within the intersection area bordered by stop
lines SL. However, in this aspect of the invention, loop detector
D5 is also divided into four portions to define four loop detectors
D5a, D5b, D5c and D5d, as illustrated in FIG. 4. As will be
described in greater detail hereinafter with reference to FIG. 6,
loop detectors D5a, D5b, D5c and D5d serve as phase A and phase B
caution (yellow) signal presence detectors. In practice, it may be
desirable to use separate loop detectors for detector D5 and its
portions D5a, D5b, D5c and D5d, as is contemplated by the
invention. For purposes of simplifying the explanation of the
invention, the loop detectors will be described with reference to
the configurations illustrated in FIG. 4.
Referring now to FIG. 5, there is shown a graphical illustration of
a method, in accordance with the invention, for controlling traffic
flow through the intersection illustrated in FIG. 4. The method
illustrated in FIG. 5 is similar to that as illustrated in FIG. 2
and, accordingly, only the deviations therefrom will be described
herein in detail. The following description given with respect to
FIG. 5 sets forth Procedure III for practicing the method in
accordance with the invention. Thereafter, a description of
apparatus for practicing the method is given with respect to the
circuit illustrated in FIG. 6.
PROCEDURE III
Briefly, the method, in accordance with the invention, for
controlling traffic flow through the intersection of phases A and B
illustrated in FIG. 4 comprises the steps of: providing a traffic
signal light S-2 for displaying go, caution and stop signals to
traffic phases A and B; energizing traffic signal S-2 to display a
go signal to phase A and a stop signal to phase B; providing
traffic monitoring means in the form of loop detectors D1, D2 for
phase A and D3, D4 for phase B for respectively developing a phase
A presence signal and a phase B presence signal so long as a
vehicle is present in the respective areas of influence of the
detectors; utilizing the phase B presence signal for controlling
energization of traffic signal S-2 to initiate termination of a go
signal displayed to phase A; providing caution signal traffic
monitoring means in the form of loop detectors D5a and D5d for
phase A and loop detectors D5c and D5b for phase B for respectively
developing a phase A caution presence signal and a phase B caution
presence signal so long as a vehicle is present in the respective
areas of influence of these detectors; and, utilizing the phase A
and phase B caution signals for respectively controlling the time
duration that traffic signal light S-2 displays a caution signal to
phase A and phase B. More particularly, Procedure III includes
Steps 1 through 4b,2 and Steps 6 through 8 of Procedures I and II,
omitting Step 5a,1 and Step 5a,2, which steps are replaced in
Procedure III with Steps 5b, 5c and 5d, as set forth below:
STEP 5b. Monitor a predetermined area of the intersection of phases
A and B by means of phase A caution presence detectors D5a and D5d
for the presence of a vehicle within the area of influence of
either detector.
STEP 5c. Recognize the presence of a vehicle in the areas of
influence of phase A caution detectors D5a or D5d, and develop a
phase A caution presence signal so long as a vehicle is present in
the area of influence of either detector.
STEP 5d. Utilize the phase A caution presence signal to control the
time duration of a phase A caution signal display so that the
signal is displayed as long as a caution presence signal is in
existence, i.e., so long as a vehicle remains in the area of
influence of detector D5a or D5d.
Upon the completion of Step 5d, i.e., when a vehicle is no longer
present in the area of influence of either detector D5a or D5d,
Procedure II Steps 6, 7 and 8 may be practiced in the event that it
is desirable to provide an all red clearance signal to phases A and
B, or if not, then upon the termination of the phase A caution
signal, Steps 1 through 5d are repeated for controlling phase B
traffic flow.
APPARATUS FOR PRACTICING PROCEDURE III
Referring now to FIG. 6, there is schematically illustrated an
apparatus taking the form of a two phase, full actuated presence
detector controller LC-2 for practicing Procedure III, described
hereinabove. Local controller LC-2 is quite similar to controller
LC-1, described with reference to FIG. 3, and includes identical
circuitry; namely, binary counter BC, binary to decimal converter
BDC, and phase A and phase B go signal control circuits C and D.
Control circuits C and D are not illustrated in FIG. 6 for purposes
of simplifying the description of the invention and, accordingly,
reference should be made to FIG. 3 for these circuits. Local
controller LC-2 does not include controller LC-1 control circuits
E, F, G and H respectively connected to converter BDC output
circuit Nos. 2, 5, 3 and 6. Instead, in accordance with this aspect
of the invention, converter BDC output circuit Nos. 2 and 5 are
respectively connected with a phase A presence caution signal
control circuit I and a phase B presence caution signal control
circuit J; and, converter BDC output circuit Nos. 3 and 6 are
respectively connected with a phase A all red clearance control
circuit K and a phase B all red clearance control circuit L.
As will become apparent from the description that follows, each
control circuit I and J includes an OR circuit in addition to an
AND circuit, a NOT circuit and a PULSE circuit, and each control
circuit K and L includes an OR circuit in addition to a NOT
circuit, a MULTIPLIER circuit and a PULSE circuit. Other than the
OR circuit, each of these circuits has been explained hereinbefore
with respect to FIG. 3 and, accordingly, for purposes of
facilitating the understanding of this invention only an OR circuit
is briefly explained below.
OR circuit. This is a static element circuit having two or more
input circuits and one output circuit. A (1) signal is present at
its output circuit so long as any one of its input circuits
receives a (1) signal. A (0) signal is present at its output
circuit so long as none of its input circuits receives a (1)
signal.
PRESENCE CAUTION SIGNAL CONTROL CIRCUITS
The internal circuitry of phase A presence caution signal control
circuit I and phase B presence caution signal control circuit J are
substantially identical, and, accordingly, only control circuit I
will be described hereinafter in detail, like components in both
circuits being identified in FIG. 6 with like reference characters.
Circuit I includes an AND circuit 42 having one of its input
circuits connected to converter BDC output circuit No. 2, and its
output circuit connected to phase A caution signal light 28A of
traffic signal light S-2 (see FIG. 4). The other input circuit of
AND circuit 42 is connected to the output circuit of an OR circuit
44 having two input circuits. One of the input circuits of OR
circuit 44 is connected to an output circuit of a presence signal
generator 46A having its input circuit connected to loop detector
D5a. The other input circuit of OR circuit 44 is connected to the
output circuit of a presence signal generator 48A having its input
circuit connected to loop detector D5d. The output circuit of OR
circuit 44 is also connected to the x input circuit of a NOT
circuit 50 having its y input circuit connected to converter output
circuit No. 2. The output circuit of NOT circuit 50 is connected to
the input circuit of a pulse circuit 52 which, in turn, has its
output circuit connected to the input circuit of binary counter
BC.
ALL RED CLEARANCE CONTROL CIRCUITS
The internal circuitry of phase A all red clearance control circuit
K and phase B all red clearance control circuit L are substantially
identical and, accordingly, only control circuit K will be
described hereinafter in detail, like components in both circuits
being identified in FIG. 6 with like reference characters. Control
circuit K includes a MULTIPLIER circuit 54 having a first output
circuit connected to an all red clearance signal light 56 of
traffic signal S-2, and a second output circuit connected to the y
input circuit of a NOT circuit 58. The x input circuit of NOT
circuit 58 is connected to the output circuit of an OR circuit 60.
The OR circuit 60 has four input circuits, one of which is
connected to the output circuit of presence signal generator 46A
which, in turn, has its input circuit connected to loop detector
D5a. Another input circuit of OR circuit 60 is connected to the
output circuit of a presence signal generator 48A which, in turn,
has its input circuit connected to loop detector D5d. A third input
circuit of OR circuit 60 is connected to the output circuit of a
presence signal generator 46B which, in turn, has its input circuit
connected with loop detector D5c. A fourth input circuit of OR
circuit 60 is connected to the output circuit of a presence signal
generator 48B which, in turn, has its input circuit connected with
loop detector D5b. The output circuit of NOT circuit 58 is
connected to the input circuit of a PULSE circuit 62 which, in
turn, has its output circuit connected to the input circuit of
binary counter BC.
OPERATION
The operation of presence detector traffic controller LC-2 is
similar to that described hereinbefore with respect to controller
LC-1 illustrated in FIG. 3 and, accordingly, only the variations
therefrom will be described hereinafter in detail. The variations
are with respect to control circuits I and K for phase A, and
control circuits J and L for phase B.
Upon the termination of phase A go extension interval No. 2,
described previously with respect to FIG. 3, a (1) signal pulse is
applied to the input circuit of binary counter BC which advances
the controller LC-2 to de-energize converter output circuit No. 1
and energize converter output circuit No. 2. Thus, a (1) signal is
applied from output circuit No. 2 to one of the two input circuits
of AND circuit 42, as well as to the y input circuit of NOT circuit
50. If no vehicles are present within the area of influence of
phase A caution loop detector D5a or D5d, then OR circuit 44
applies a (0) signal from its output circuit to the x input circuit
of NOT circuit 50. Accordingly, a (1) signal is applied from the
output circuit of NOT circuit 50 to the input circuit of PULSE
circuit 52 which converts the signal into a (1) signal pulse for
application to the input circuit of binary counter BC. This
advances the controller to de-energize converter output circuit No.
2 and energize converter output circuit No. 3. However, if a
vehicle is in the area of influence of either loop detector D5a or
D5d, then a (1) signal is present on the output circuit of OR
circuit 44. This prevents a (1) signal from appearing on the output
circuit of NOT circuit 50 and completes the second of the two input
circuits of AND circuit 42 for energizing phase A caution signal
light 28A. Signal light 28A remains energized so long as a vehicle
is present in the area of influence of loop detector D5a or D5d. If
a vehicle was present and then left the area of influence of both
loop detectors D5a and D5d, a (1) signal will not be present on the
output circuit of OR circuit 44. This will de-energize the phase A
caution signal light 28A. Also, since a (1) signal is not present
at the x input circuit of NOT circuit 50, and a (1) signal is
present on the y input circuit, then a (1) signal is applied from
the output circuit of NOT circuit 50 to the input circuit of PULSE
circuit 52 which converts the signal to a (1) signal pulse for
application to binary counter BC. This advances the controller to
de-energize converter output circuit No. 2 and energize output
circuit No. 3.
With converter BDC output circuit 3 energized, a (1) signal is
applied through MULTIPLIER circuit 54 to energize the all red
clearance light 56 to display a stop signal to both phase A and
phase B. Also, a (1) signal is applied through MULTIPLIER circuit
54 to the y input circuit of NOT circuit 58. So long as a vehicle
is present in the area of influence of loop detector D5, i.e., any
of its sub-loop portions D5a, D5b, D5c or D5d, a (1) signal is
present at the output circuit of OR circuit 60, as well as on the x
input circuit of NOT circuit 58. Thus, a (1) signal is not present
on the output circuit of NOT circuit 58 and, accordingly, the all
red clearance light 56 remains energized. However, when no vehicle
is present in the area of influence of loop detector D5, i.e., not
present in either the area of influence of either loop detector
D5a, D5b, D5c or D5d, a (1) signal is not present at the x input
circuit of NOT circuit 58. Thus, a (1) signal is present on the
output circuit of NOT circuit 58 which is converted into a signal
pulse by PULSE circuit 62 for application to binary counter BC.
This advances the controller to de-energize converter BDC output
circuit No. 3 and energize output circuit No. 4.
The operation of control circuits D, J and L for phase B traffic
flow is identical with that just described with respect to control
circuits C, I and K and, accordingly, no further description is
deemed necessary for complete understanding of the operation of
local controller LC-2.
Although the invention has been shown in connection with various
preferred procedures for practicing a method in accordance with the
invention, as well as apparatus for its practice, it will be
readily apparent to those skilled in the art that various changes
in procedure, as well as in form and arrangement of parts, may be
made to suit requirements without departing from the spirit and
scope of the invention as defined by the appended claims.
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