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Micro-Simulation of Automated Vehicleswith Minimal Central Control
Advanced Transit Association Annual Technical Meeting
January 12, 2008
Washington, DC
Robert Johnson
R. E. Johnson ConsultingRockville, Maryland
www.REJConsult.com
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Different Types ofAutomated Transit Vehicles
• Track based
– Run on special track that provides lateral guidance and power (most People Movers are in this category)
• Automated Road Vehicles
– Steer themselves along a flat surface without mechanical guidance
– Have a self-contained power supply
– Max speed 20 - 25 mph (32 - 40 kph) on exclusive roadway
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Examples ofSmall Automated Road Vehicles
CyberCab: proposed by 2getthere which operated the first public ARV
ULTra: scheduled to begin service in 2009 at Heathrow airport, London
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Presentation: Three Related Topics
• Micro-simulation model for Automated Road Vehicles
• Using the model to demonstrate a simple vehicle-based control strategy
• Simulation of a shuttle application
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Simulation represents guideway as straight segments alternating with circular arcs
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Library of Special Guideway Elements(in Various Stages of Development)
• End-of-line station
• Center platform station
• “T” Intersection
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Vehicle-based Control System:How to Handle Conflicts
• Vehicles know the complete layout of the system, and know exactly where they are
• At each merge or crossing point, one lane always has priority
• If a vehicle is in the low priority lane, it uses its sensors to scan the high priority lane, and yields if a vehicle is detected
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Vehicle in Low Priority Lane Yields
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Vehicle-based Control System (cont.)
• Vehicles use sensors to watch for objects in their path (another vehicle or foreign object)
• If unexpected object detected, vehicle stops and notifies human operator at central control
• Central control computer:
– Assigns destinations to vehicles
– Holds vehicles at stations to smooth system flows
– No safety-related functions
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Example Application - Shuttle
• Two-way guideway with a station at each end
• Six-passenger, shared vehicles
• 5 second minimum headway
• Maximum passengers per hour per direction
– 4320 theoretical (6*3600/5)
– Practical maximum is probably between 1000 and 2000
• Better than conventional people mover shuttle since can give riders very short wait times (say, 60 sec max)
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(Very Short) Shuttle UsingAutomated Road Vehicles
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End-of-Line StationOutbound paths
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End-of-Line StationInbound paths - Vehicles back into berths
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Path-Crossing ConflictVehicle Leaving Berth Yields
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Merge ConflictVehicle From Berth Nearer Exit Yields
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Merge Conflict Leaving Station
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Vehicles Crossing Paths
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Simulation of Complete Shuttle
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Conclusions and Future Work
• Vehicle-based control seems feasible, at least in simple systems
• Shuttle systems could be implemented at very low cost, after development of electronics for vehicle
• Next step: develop detailed operating rules for vehicles in T intersections and center platform stations
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