Micro-Simulation of Automated Vehicles
with Minimal Central Control
Advanced Transit Association Annual Technical Meeting
January 12, 2008
Washington, DC
Robert Johnson
R. E. Johnson Consulting
Rockville, Maryland
www.REJConsult.com
Different Types of
Automated 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 of
Small Automated Road Vehicles
ULTra: scheduled to begin
service in 2009 at Heathrow
airport, London
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CyberCab: proposed by
2getthere which operated
the first public ARV
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Presentation: Three Related Topics
• Micro-simulation model for Automated Road
Vehicles
• Using the model to demonstrate a simple vehiclebased 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 Using
Automated Road Vehicles
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End-of-Line Station
Outbound paths
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End-of-Line Station
Inbound paths - Vehicles back into berths
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Path-Crossing Conflict
Vehicle Leaving Berth Yields
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Merge Conflict
Vehicle From Berth Nearer Exit Yields
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Merge Conflict Leaving Station
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.WMV file was
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OR
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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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