Method and means for network control of traffic

• US 6,496,773 B1
• Filed: 07/27/2000
• Issued: 12/17/2002
• Est. Priority Date: 01/30/1998
• Status: Expired due to Fees

• Current Assignee: Kjell Olsson
• Original Assignee: Kjell Olsson
• Inventors: Olsson, Kjell
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Hernandez, Olga
• Application Number:
  US09/601,116
• Time in Patent Office: 873 Days
• Field of Search: 701/117, 701/118, 701/200, 701/119
• US Class Current: 701/117
• CPC Class Codes: G08G 1/01 Detecting movement of traffic to be counted or controlled G08G1/07 - G08G1/14 take precedence

Abstract

The invention relates to a method for detection and prediction of incidents and traffic queues formed by overloading. This is done in real time with use of sensors in a road network. Predictions are used also to reach a faster and more reliable detection. Sensor measurements are also used in the process, where the comparison with expected values are used for successively updating stored parameter values for the involved algorithms. By this, the system can succeedingly adapt itself for changed situations. The strong traffic variations, that are naturally occurring at short time intervals are treated with the use of noise-based methods. By this, there are formed distribution related measures as e.g. the standard deviation, which can be estimated from measurements, and submit a base for estimating probabilities for deviations of a certain size, e.g. related to the standard deviation. Automatic incident detection (AID) is based on determination of the desired false-alarm rate, and the related threshold level. The method includes accumulated measurements. Faster and more reliable incident detections are received with the use of the invented prediction process method.

Claims

1. A method for managing traffic in a road network, comprising:

a selection of different roads selected from the group consisting of at least one of motorways, larger roads, a thoroughfare, entrance roads, and subareas of the network,

wherein subnetworks in city areas include road network of streets with crossings, and where the network includes road links which are connected with each other via nodes,

wherein said nodes can connect a variable number of links, and be designed in different ways, wherein said roundabouts are included and various types of intersections; and

wherein sensors and control means for traffic are positioned at selected links in the network, and wherein the traffic management includes a task to preserve and utilize a large capacity on selected parts of the road network,

wherein capacity at a selected cross section includes the maximum traffic flow which can pass the cross section, and including performing said task during a time period when the traffic volume and need for capacity are large, and wherein the method for traffic management is based on selected basic principles, and is characterized by;

a. reducing blocking and risk for blocking of flows on links, whereby blocking is meant cars that standing still or with low velocity wholly or partly are blocking one or several lanes for in-flows or passing through flows on a link;

b. performing step (a) by limiting the upstream flow to reduce the risk for blocking downstream link;

c1. performing step (a) by determining flow rations for selected parts of the network, and the ration being a target value at the control of the size of a flow to a link or a node;

c2. performing step (c1) with application of step (b), where the ration for a link is determined, including a judgment of the risk for blocking of said link;

c3. performing step (c2) for selected links in addition of determining the ration for a link, where also the risk for blocking downstream link is judged at the ration determination, and is based on the ration for in-flows to a link being governed by the out-flow from the link, and is the out-flow from the link via downstream node dependent on rations, which are given to exit links from said downstream node, and dependent on limitation, which are given by controlling flows through the node from entrance links of the node to exit links of the node;

d1. for a node with at least one upstream link performing step (a) by measuring flows on at least one of this link, other upstream links and downstream links;

d2. measurements according to step (d1) being used for the method step of comparing estimated flow values, based on said measurements, with at least one of;

assigned rations and settings of control for controlling the out-flow from at least one of upstream links of said node, and when deviations are larger than selected values, performing actions according to at least one of steps (e)-(f) as follows;

e. analyzing if said deviaton according to step (d2), indicates that at least one of said links are or will be blocked or has a margin to handle said deviation; and

f. assigning corrected settings of the control selecting at least one of;

said links and their upstream links.

2. A method according to claim 1, characterized by:

d1. for a node with at least three links, performing the step of measuring distributed flows (subflows) on at least one of those links regarding flows upstream the node for at least two of;

turn left V, turn right H, continue straight ahead R, and a combination of two of those in said node;

d2. using measurements step (d1) for comparing the measured flows with the settings of the control for controlling out-flows from the link, and when the deviation is larger than a selected value, performing actions according to at least one of steps (e)-(f) as follows;

d3. using measurements according to step (d1) for determining input flows to at least one of the links downstream said node;

d4. according to step (d3), comparing estimated sizes of input flows on a link with the ration for the link, and if the deviation is larger than a selected value, performing actions according to at least one of steps (e)-(f) as follows;

e. analyzing if said deviation according to steps (d2) and (d4) respectively, indicates that at least one of said links are blocked or has a margin to handle said deviation;

f. assigning control for correcting the setting on at least one link of said links and the upstream links.

3. A method according to claim 1, characterized by;

k1. for a node with at least three input and three output links, including a four road crossing with four entrance and four exit links, performing the method step of measuring distributed flows on at least one of those entrance links regarding the flows upstream the node for at least two of;

turn left V, turn right H, continue straight ahead R, in said node;

k2. using measurements according to step (k1) for the step of comparing the measured flows with the settings of the control for controlling out-flows from the link, and when the deviation is larger than a selected value, performing actions according to at least one of steps (e)-(f) as follows;

k3. using measurements according to step (k1) for determining input flows to at least one of the exit links downstream said node, and thereby adding together flows from different entrance links based on said measurements;

k4. according to step (k3), comparing estimated sizes of input flows on a link with the ration for the link, and if the deviation is larger than a selected value, performing actions according to at least one of steps (e)-(f) as follows;

e. analyzing if said deviation according to steps (k2) and (k4) respectively, indicates that at least one of said links are blocked or has a margin to handle said deviation;

f. assigning control setting on at least one link of said links and the upstream links.

4. A method according to claim 1, characterized by;

e1. performing the step of determining at least one margin for a link to handle a time limited large flow without blocking the link, and where a margin is related to at least one of steps (e2)-(f3) as follows;

e2. prerequisites on the link and the surrounding road network, including prerequisites on a margin, being composed of allowed buffer queue size on at least one of;

on a selected lane of said link and totally on the link;

f1. performing the step of dynamically setting control for controlling out-flows from a link;

f2. assigning, control according to step (f1), a ration-setting, which corresponds to ration-values of the link;

f3. assigning a corrected setting, to control according to step (f1) and considering margins according to step (e1), when deviations from the ration-setting are required on at least one link of;

said link and upstream links.

5. A method according to claim 1, characterized by;

n1. for a motorway node being an entrance node, performing the step of measuring upstream flows on the motorway and the entrance road;

n2. from measurements according to step (n1), predicting entering flow to a downstream entrance node, and comparing that flow with the corresponding ration, and if the difference is larger than a selected value, perform actions according to step (n7);

n3. performing the step of determining margins for a motorway link to handle large flows without the link being blocked;

n4. a margin according to step (n3), said margin including the allowed size of the buffer queue on a motorway link according to at least one of on a selected lane of the link and totally on the link;

n5. performing the step of dynamically setting of control for controlling out-flows from a link;

n6. assigning, to control according to step (n5), a ration-setting, which corresponds to ration-values of motorway links connected to the node;

n7. assigning a corrected setting according to step (n5), to control according to step (n5) and selectively considering step (n3), on at least one of;

said downstream entrance and its upstream entrances.

6. A method according to claim 5, characterized by, the entrances of the motorway being connected to a road network, and that the entrance flow controls are fed back upstream along the road network for further traffic control at said network.

7. A method according to claim 5, characterized by;

a buffer queue on a motorway exit road having a margin determined by at least one of the following;

a. the queue is not growing upstream on to the motorway and blocking passing flows there;

b. when the passing flows can be limited to fewer lanes, the queue margin can be increased to a queue length reaching up to the motorway and to the next exit, loading one lane, usually the right one,

c. the queue on the motorway is not growing past the exit node, such that cars aiming for the exit, will be blocked by the motorway queue;

d. the queue on the motorway is arranged to pass the exit on the motorway, leaving on the closest lane, usually the right one, at least one gap free at or upstream the node, such that upstream cars, which are to turn to the exit, wouldn'"'"'t be blocked by said motorway queue, and that the margin in this way can be expanded until other conditions are limiting the queue-length.

8. A method according claim 1, characterized by;

L1. at least one lane of a link being appointed as a “

queue lane”

, that cars, which are going to queue, join a queue in this lane, and that at least one of the lanes is appointed being free from parallel queues;

L2. the “

queue lane”

queue starting upstream an exit zone, which is occupying the space closest to the link exit to the node, and that the exit zone is reserved for cars which are to pass out from the link during the current controlled passage phase, otherwise called a “

green phase”

;

L3. selectively, allowing also cars waiting for the next queue-phase, to join after those cars mentioned in step (L2);

L4. control showing those cars that will pass out in the synchronized “

green phase”

their travel on the queue-free lane into the exit zone;

L5. the exit zone being designed in that way that at least one lane can be used by exiting cars.

9. A method according to claim 1, characterized by;

L1. equipping a link with at least two queue-pockets along at least one of the lanes, here exemplified with the right one, and where said queue-pockets are representing the out-flows of the link in this example three flows;

V, R, H, in an order, in which the respective outflow is controlled by the help of the green phases of the control, whereby green phase is meant letting through of traffic, and where phase (0) is the current or the closest to begin green phase for at least one of V, R, H, and the first queue-pocket is for phase (1), which is the next green phase for the direction in order and phase (2) is after that the next following, and selectively there may also be one queue-pocket for phase (0);

L2. arriving cars to the link, according to given information, are driving into their respective queue-pocket, dependent on which direction;

V, R or H, the car will select in the downstream node, and the queue-pockets respective the current phase (0) are filled successively until the respective green period-volume or pocket is full, and after a full phase (0) said possibly selected queue-pocket;

phase (0) is filled, while cars representing phases with full queue-pockets or full green period volumes are queuing behind in the order of arrival; and

as time is passing and the green phases change, the queue-pocket for phase (1) is being emptied and filled by the cars behind from the queue-pocket for phase (2), which now turns to a new phase (1) in the queue-pocket (1); and

to the extent a queue-pocket will be filled with more cars, it will be filled from behind by arriving cars to the link, or from a possible queue behind the queue-pockets;

L3. keeping the lane next to the queue-pockets open for the transports to the respective queue-pocket,

L4. using also the adjacent lane for the out-flow from queue-pocket (1) downstream, whereby at least two lanes can be used for the respective green phase direction, and a large out-flow from the link can be provided during a selected time period;

L5. obtaining information by use of sensors about the volume in the queue-pockets and a possible queue behind the queue-pockets, and that presentation means control the queue-pocket allocation and the out-flows from the link;

L6. using information about said volumes to determine input flows to at least one of the exit links downstream said node.

10. A method according to claim 9, characterized by;

M1. dividing the respective queue-pocket in at least two subpockets representing the output flows of a downstream link, here exemplified with three flows;

V, R, H in upstream order;

M2. arriving cars to the link, according to given information are driving into their respective subpocket of the queue-pocket dependent on which direction;

V, R or H, which the car will select in the node of said downstream link;

M3. hereby basing the flow to a link of the downstream node on ordered packets of cars, subpocket for subpocket from link after link, and thereby providing a presorting per queue-pocket on said downstream link and also a presorting in the possible queue, which might be formed upstream the queue-pockets of the link;

M4. selectively, at the out-flow from queue-pocket (1), distributing subpockets on lanes adapted to the phases of the downstream link, such that the subpocket corresponding to that green phase of the downstream link, which is the phase after the travel time, usually its phase (0), obtains allowance to the adjacent lane or exit;

M5. a subpocket on a first link containing information about future input flows to a second link, which is a downstream link of a downstream link of the first link, and there can be identified several equivalent links to said first link, as being upstream links of upstream links of said second link and selectively predicting said input flows from said information per respective subpocket on the first link and selected equivalent links of this first link.

11. A method according to claim 9, characterized by;

the margin being composed by a buffer queue on the motorway link downstream an exit node, and that the margin is determined by at least one of the following conditions;

a. the queue on the motorway is not growing past the exit node, such that cars aiming for the exit, will be blocked by the motorway queue;

b. the queue on the motorway is arranged to pass the exit on the motorway, leaving on the closest lane, usually the right one, at least one gap free at or upstream the node, such that upstream cars, which are to turn to the exit, wouldn'"'"'t be blocked by said motorway queue, and that the margin in this way can be expanded until other conditions are limiting the queue-length.

12. A method according to claim 1, characterized by;

L1. performing control of out-flow from a first link regarding the subflows of the link, which subflows are based on the out-flow directions of the link;

L2. dividing said subflows in subsubflows, which regard subflows of downstream links, and controlling out-flow from the first link by including control of at least one of said subsubflows.

13. A method according to claim 1, characterized by;

L1. further developing the steps, concerning control of flow on a first link to at least one second link, which is a link at least one link downstream downstream link of the first link;

L2;

control for controlling the marking of selected links on a simple presentation model of the topic downstream road network, and with selected information indicating at least one of;

passage allowance for cars to at least one selected link;

passability problem on at least one selected link.

14. A method according to claim 1, characterized by;

a. a link or node obtaining reduced capacity caused by incidents or other blockings which reduce the flow more than the respective ration, said link respective of the upstream links of said node then are given dynamically corrected rations, related to the limited capacity;

b. changes of rations according to step (a), being fed back at least one step upstream, to selected second links upstream said links in step (a), and if the result is differing more than a selected value from the rations of said second links, those links are given dynamically corrected rations;

c. selectively, changing of rations according to step (a), being fed back at least one step downstream, to selected third links downstream said links to step (a), and if the result is differing more than a selected value from the rations of said third links, those links are given dynamically corrected rations.

15. A method according to claim 1, characterized by;

a. at traffic management with flow distribution on links according to given ratios, leaving information to car drivers about route selection, and thereby decreasing or increasing flows on selected downstream links, to prevent exceeding respectively to utilise the rations of said links;

b. performing step (a) with dynamic information, when the traffic management operates according to dynamically corrected rations.

16. A method according to claim 1, characterized by;

a1. analyzing a margin for a link, considering extra in-flow above the ration, which might be allowed regarding the link out-flow;

a2. analyzing if any flow above the link ration can be let out from the link, including at least one of the following;

b1. analyzing a margin for a link, considering extra out-flow above the ration, which might be allowed regarding other links out-flows to the node and the limited capacity of the node;

b2. analyzing a margin for at least one downstream link, considering extra in-flow above the ration;

b3. analyzing a margin regarding buffer queue for at least one downstream limit.

17. A method according to claim 1, characterized by;

predicting the input flow to a first link from measurements on other selected links, which are upstream links of upstream links to said first link;

a. comparing said predicted flow with the ration for said first link, and if the deviation is larger than a selected value, analyzing and performing at least one action on selected upstream links up to and including said other links;

b. selecting said action from the group;

utilizing a link margin, including queue buffering;

reducing a link out-flow;

feeding back an action on a link for analysis of possible action on at least one upstream link.

18. A method according to claim 1, characterised by;

performing selected actions on selected links in the road network and selecting the actions from a group including the following;

utilizing a link margin, including queue buffering;

reducing a link out-flow;

feeding back an action on a link for analysis of possible action on at least one upstream link;

information to car drivers regarding choice of route.

19. A method according to claim 1, characterized by;

at least one entrance link to a first node in a subnetwork, being assigned at least one of the following;

a. a dynamic ration correction;

b. a control means, which limits the out-flow from the link;

and where the ration correction respective the out-flow limitation is carried out on purpose to decrease blockings in the subnetwork and the respective size is determined based on selected criterias at analysis of results from at least one of steps (c)-(d) as follows;

c. estimation of the deviation between in-flow and out-flow of the subnetwork;

d. estimation of the total or relative traffic volume in the subnetwork.

20. A method according to claim 1, characterized by;

a. performing ration determination and ration correction with steps, where links with limited in-flows are detected and studied;

b. identifying main directions for large limited flows and performing at least one of steps (c)-(e) as follows;

c. when at least one of parallel links have space for more flows up to the ration level, performing control of flow from at least one of said limited links to said link at a position upstream said link;

d. when several parallel links have said limitation, performing analysis of the increase of flow passage on at least one of said links, in said main direction through nodes, with start downstream, and when the ration can be increased, the analysis continues upstream against the main direction, to successively upstream positioned nodes and links, for possible increase of rations in the main direction;

e. increasing rations in the main direction, requiring a decrease of rations in the cross direction through common nodes, and parts of the need of cross flows further upstream in the road network are controlled by actions, according to the step, that car drivers early upstream are managed to search cross connection for such a route in the road network, that in its main direction is heading more direct to the destination;

f. concentrated problems at subnetworks with larger traffic demand than capacity, including incident problems, analyzing the upstream possibilities to manage traffic to less utilized links around the problem area, and in the control actions there is included a setting of dynamically changed ration values at traffic changes including incidents.

21. A method for managing traffic in a road network, comprising:

a selection of different roads selected from the group consisting of at least one of motorways, larger roads, a thoroughfare, an entrance road, subareas of the network,

wherein subnetworks in city areas include road network of streets with crossings, and wherein the network (includes road links connected with each other via nodes,

wherein said nodes can connect a variable number of links, and be designed in different ways, wherein roundabouts are included and various types of intersections;

wherein sensors and control means for traffic are positioned at selected links in the network, and wherein the traffic management includes a task to preserve and utilize a large capacity on selected parts of the road network,

wherein capacity at a selected cross section includes the maximum traffic flow which can pass the cross section, and

including performing said task during a time period when the traffic volume and need for capacity are large, and wherein the method for traffic management is based on selected basic principles, and is characterized by;

a. reducing blocking and risk for blocking of flows on links, whereby blocking is meant cars that standing still or with low velocity wholly or partly are blocking one or several lanes for in-flows or passing through flows on a link;

b. performing step (a) by limiting the upstream flow to reduce the risk for blocking downstream link;

c1. performing step (a) by determining flow rations for selected parts of the network, and the ration being a target value at the control of the size of a flow to a link or a node;

d1. at least one area being arranged as queue buffer with connection to said link, that cars can be controlled to join any queue in this queue buffer, and that at least one stretch of a lane parallel to said queue buffer is determined to be free from queues;

d2. arranging the queue buffer upstream an exit zone, which is occupying the space closest to the link exit to the node, and that the next zone is reserved for cars which are to pass out from the link during the next beginning or already currently controlled passage phase, called a “

green phase”

;

d3. selectively, also allowing cars waiting for the next queue-phase, to join after those cars mentioned in step (d2);

d4. control for showing those cars that will pass out in the synchronized “

green phase”

, their travel on the queue-fee lane into the next zone;

d5. the exit zone being designed in that way that at least one lane can be used by exiting cars.

22. A method according to claim 21, characterized by;

controlling out-flow from the link regarding a passage phase for left turning (V) and further at least one passage phase for straight ahead (R) and right turning (H), and that V-cars are queueing in said queue buffer waiting for control for connecting to said exit zone, thereby preventing that V-cars are blocking R or H-cars in the exit zone during the passage phase of those cars, and controlling V-cars out from the queue buffer in a controlled number, matched in time for not being blocked by R- or H-cars during V-cars passage phase; and

that R- and H- as V-cars can utilize the link exit lane capacity for respective direction.

23. A system for managing traffic in a road network, comprising:

a selection of different roads selected from the group consisting of at least one of motorways, larger roads, a thoroughfare, entrance roads, subareas of the network,

wherein subnetworks in city areas include road network of streets with crossings, and

wherein the network consists of road links, which are connected with each other via nodes, wherein said nodes can connect a variable number of links, and be designed in different ways, wherein roundabouts and four road crossings are included and various types of intersections; and

wherein sensors and control means for traffic are positioned at selected links in the network, and wherein the traffic management includes a task to preserve and utilize a large capacity on selected parts of the road network,

wherein said capacity at a selected cross sections includes the maximum traffic flow which can pass the cross section, and

including performing said task during a time period when the traffic volume and need for capacity are large, and wherein the method for traffic management is based on selected basic principles, which means includes traffic management system, traffic sensors and control means characterized by;

a. a traffic management system including;

a1. communication equipment, which transfer information from sensors about traffic on different links in the road network and transfer output information to control means;

a2. a computer unit which perform processes regarding;

a3. reduction of blocking and risk for blocking of flows on links, where blocking means cars that standing still or with low velocity wholly or partly are blocking one or several lanes for in-flows or passing through flows on a link;

a4. where process (a3) includes the process of limiting the upstream flow to reduce the risk for blocking downstream link;

a5. rations, where rations for traffic flows are determined for selected links and are stored;

a6. estimation and predicting of flows for selected links;

a7. corrections, where dynamic ration-corrections are calculated after analysis of measured or predicted flow values compared to corresponding rations;

a8. margins for selected links;

a9. control information regarding limitations of out-flows from selected links;

a10. deviations in traffic from valid ration for a selected link, and corrections of control information for at least one of;

said link and upstream links;

b. sensors are selected for generation of traffic information including at least one of;

flow information,

velocity information

queue length information

information about numbers of cars (volume)

c. control means which are selected for control of traffic, including at least one of

control of out-flows from links

information about route choice

information regarding choice of lane

information regarding passability

and where road links are equipped with queue-pockets respective subpockets;

information regarding queue-pocket

information regarding subpocket.

24. A system according to claim 23, characterized by;

a. said traffic management system being a computer based real time system;

b. said sensors being at least one of;

loop-sensors at the road

video-sensors

radar-sensors

infrared-sensors

infra- or ultra-sound sensors

video-sensors for information about queue-pockets or subpockets

c. said control means being at least one of;

light signals

variable signals (mechanical or electrical).