Multiagent Traffic Management: An Improved Intersection Control Mechanism Mechanism PRESENTED BY PATRICIA PEREZ AND LAURA MATOS PRESENTED BY: PATRICIA PEREZ AND LAURA MATOS
Outline � Introduction � The Original System � Improving the Original Model p g g � Protocol � Intersection Control Policies � Empirical Rules � Discussion and Related Work Discussion and Related Work � Conclusion
Introduction Introduction This work is based on the need to create a new system that will reduce traffic congestion. This is a problem that leads to loss of productivity and decreasing in standards of living in urban settings. Intersection control t d d f li i i b tti I t ti t l mechanisms have been developed to provide alternatives in multi-agent traffic management. An original model in multi agent traffic management. An original model which is known as a reservation based multi-agent approach is under study at this moment. This work will describe an improved version of this mechanism.
The Original System � System consists of two types of agents: intersection y yp g managers and drivers � “Call ahead” system � “Reservation” system � Compared the reservation system to other systems like the traffic light and overpass
Improving the Original Model � Agents should only communicate when necessary � Agents should only have access to information which can be reliably obtained with current technology � Communication failures should not impact safety of f l h ld f f system � Vehicles are treated as individual agents and no � Vehicles are treated as individual agents, and no controller should exist � Agents should only have minimal knowledge about each g y g other � Every vehicle should make it through the intersection
Improving con’d � Acceleration in the intersection � Before it only allowed for constant speed through the intersection = not realistic � How to choose acceleration? H t h l ti ? � Tries to speed up to limit � If that does not work then it goes to constant velocity � If not, then request is rejected
Improving con’d � Stopped the needless communication between pp agents, had always known other’s states which is not realistic � Came up with another, easier protocol by which to have them communicate to intersections � Solved three problems: S l d h bl � Communication goes through one monitorable channel which is easier to work with is easier to work with � With less messaging ability, no agents can control others � Now everyone “speaks the same language”
Protocol Protocol This was created so that the agents can communicate the bare minimum of information necessary to function appropriately. This protocol consists of several message types for each kind of agent, as well as some rules governing when the messages should be sent and what sorts of guarantees accompany them. Messa ge Ty p es – The vehicles and intersection manager are each Messa ge Ty p es The vehicles and intersection manager are each • restricted to a few types of messages with which they must coordinate. Protocol Actions – In addition to message types, the agents involved • (the vehicles and the intersection) must be obey a set of rules.
Message Types Message Types Vehicle � Intersection Vehicle � Intersection There are four types of messages that can be sent from vehicles to the intersections: Req uest - This is the message a vehicle sends when it does not • have a reservation and wishes to make one. Cha nge-Req uest – This is the message a vehicle sends Cha nge Req uest This is the message a vehicle sends • when it has a reservation, but would like to switch to a different set of parameters. Ca ncel – This is the message a vehicle sends when it no longer Ca ncel This is the message a vehicle sends when it no longer • • desires its current reservation. Reserv a tion-Com p leted – This message is used when • the vehicle has completed its traversal of the intersection. h hi l h l d i l f h i i
Message Types Message Types Intersections � Vehicle Intersections � Vehicle There are three types of messages that can be sent from the intersection to the individual vehicles: Confirm a tion – This message is response to a vehicle’s • REQUEST (or CHANGE-REQUEST) message. It can contain a counter-offer by the intersection. Rejection – By sending this message, an intersection can • inform a vehicle that the parameters sent in the latest REQUEST (or CHANGE-REQUEST) were not acceptable, and that the ( Q ) p b , intersection either could not or did not want to make a counter- offer. Acknow led gm ent – This message acknowledges the receipt Acknow led gm ent This message acknowledges the receipt • of a CANCEL or RESERVATION-COMPLETED message.
Protocol Actions Protocol Actions Vehicles Actions 1. A vehicle may not enter the intersection without a reservation. 2. If a vehicle is going to cross the intersection, it must do everything reasonable within its power to cross in accordance with the parameters included in the most recent CONFIRMATION message it has received from the intersection. 3. If a vehicle sends another message before the intersection manager has sent a response, the intersection manager may choose to ignore it. Thus, a vehicle should only send a message if it has received a response to its previous message. 4. If a vehicle has not yet entered the intersection and does not have a reservation, it may send a REQUEST message. If it has not yet entered the intersection and does have a reservation, it may send either a CHANGE-REQUEST or CANCEL message. If it sends any of these messages when it is not allowed to, the intersection may choose to ignore them. 5. If a vehicle has a reservation and has successfully crossed the intersection, it may send a RESERVATION- COMPLETED message. 6. If a vehicle receives a CONFIRMATION message, it is considered to have a reservation.
Protocol Actions Protocol Actions Intersection Actions • When an intersection receives a REQUEST message, it must respond with either a CONFIRMATION or a REJECTION message. If it responds with a CONFIRMATION message, it is guaranteeing that no cross-traffic will interfere with the vehicle if it crosses the intersection in accordance will interfere with the vehicle if it crosses the intersection in accordance with the parameters in the message. • When an intersection receives a CHANGE-REQUEST message, it must respond with either a CONFIRMATION or a REJECTION message. If it responds with a CONFIRMATION message, it is guaranteeing that no d i h i i i h cross-traffic will interfere with the vehicle if it crosses the intersection in accordance with the parameters in the message. Any previous guarantees are nullified. • When an intersection receives a CANCEL message, it must respond with an ACKNOWLEDGMENT message. Any guarantee that had been made to the sending vehicle is nullified.
Intersection Control Policies � Overpass accepts everything, mostly for testing p p y g, y g purposes � Reservation System � Stop Sign � Traffic Light
New Driver Agent New Driver Agent Extensions to the driver agent: g • Optimism and Pessimism • Cancellation and Communication Complexity C ll i d C i i C l i
Optimism and Pessimism Optimism and Pessimism • An optimistic agent makes a reservation assuming it will p g g immediately get to accelerate to full speed. An agent which no longer finds itself stuck behind a slower vehicle will become optimistic and attempt to make a new will become optimistic and attempt to make a new, earlier reservation. • A pessimistic agent assumes it will be stuck at it current velocity until it reaches the intersection. If an agent has to cancel its reservation because there is no way for it to arrive on time it becomes pessimistic arrive on time, it becomes pessimistic.
Cancellation and Communication C Complexity l i Cancellation: The new agent only cancels a reservation if there is absolutely no • physical way it could reach the intersection on time. Communication Complexity: i i l i Reducing the communication complexity of the system is very important for two reasons: If fewer total messages are sent, the bandwidth required to send • messages is lower; thus given the available bandwidth, messages are much less likely to be delayed or lost- events which might negatively affect the system’s efficiency. y y Many of the messages (like REQUEST and CHANGE-REQUEST • messages) directly result in intense computation by the intersection manager. Because the resources of the intersection manager are limited it can only process these messages at some fixed rate limited, it can only process these messages at some fixed rate.
Demonstration � http:/ / www.cs.utexas.edu/ users/ kdresner/ aim/ ?p=vi deo
Empirical Results � Simulation settings g � Overpass Results � Reservation System Results y � Stop Sign Results � Allowing Turns from Any Lane g y � Changes to Driver Agent
Future Work Future Work • Investigate what happens when vehicle are allowed to g pp turn into any lane. • With the creation of a communication protocol, create more interesting driver agents and intersection i t ti d i t d i t ti managers. • More research in designing more intelligent reservation More research in designing more intelligent reservation systems and driver agents.
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