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ATMS
Advanced Traffic Management Systems
Arterial Control Systems
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ATMS
• Intent of ATMS:
– Improve operational control
– Adapt control strategies to current/expected
traffic
– Provide marginal improvements to system
capacity or throughput– Reduce congestion / delay / queues
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ATMS Requires
• Control mechanism
• Surveillance function
• Communications
• Data manipulation
• Control algorithm• Maintenance function
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Arterial ATMS – Traditional
Control
• Fixed timing plans assume
– Fixed volumes
– Fixed O/D patterns
• Traffic volumes are not constant – it!in an !our
– "et#een !ours
– From day to day
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Arterial ATMS – Traditional
Control• $eople ad%ust t!eir traffic patterns
– &et#or' timing plans often use o(solete O/D
patterns
• Significant c!anges in timing plans are
disruptive to traffic flo#
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Adaptive Control
• &et#or' timing plans are difficult to c!ange
significantly
– Traditional timing plan c!anges cause ma%or
disruptions in progression ) congestion
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Arterial Solution – Adaptive
Control• Adaptive control*
– Small modifications to t!e current timing plan
to optimi+e ve!icle movements
– Dependent on surveillance inputs
– ,e-uires optimi+ation algorit!m
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.xamples of TMS
• Arterials Control Systems– Actuated & semi-actuated control
– SCOOT– SCATS
– OPAC
– NSATMS– RT-TRACS
– RHODES
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Arterial ATMS
• Simplistic version of adaptive control*
– Signal actuation
• Adaptive control (ecomes more difficult if
more significant c!anges are desired
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SCOOT
• Split Cycle Offset Optimi+ation Tec!ni-ue
• "ritis!
• "asically on0line Transyt optimi+ation
• Ma'es only minor ad%ustments to t!e current plan
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SCOOT
• 1ses upstream detector locations
– Must estimate -ueues / saturation
– "ut counts very #ell
• Optimi+es a performance index minimi+ing
– delays
– stops
– congestion
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SCOOT
• Ad%usts
– cycle times
– p!ase times
– offsets
• Attempts to !old t!e most congested
intersection at 23 percent of saturation
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SCATS
• Sydney Coordinated Adaptive TrafficSystem
• Australian
• Controls delay and stops – doesn4t actually
optimi+e
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SCATS
• 5ierarc!ical su(system (ased
• Selects 6(est7 splits cycle offsets forcritical intersection #it!in eac! su(system (ased on measured saturation level t!en
• determines (est coordination plan for ot!ersu(system intersections
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SCATS
• 1ses long 89:; m< stop (ar detectors
– "etter saturation measurement
– "etter -ueue measurement
– 5arder to compute volume
• Only incremental c!anges allo#ed eac!cycle
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SCATS
• Su(systems are lin'ed #!en (ot! !ave t!e
same optimum cycle lengt!
• Su(system lengt!s can (e (ro'en if no
(enefits are present
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O$AC
• Optimi+ation $olicies for Adaptive Control
• =solated intersection program 8sinceexpanded<
• 1ses a simplified dynamic programmingapproac! to optimi+e a performance value8delay<
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O$AC
• 1ses advanced detectors 8li'e SCOOT<
• $redicts flo#s 8arrival time and total
volume< (ased on previous time periods
• Allo#s c!anges in cycle p!asing etc:
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&SATMS 8as designed<
• Does not actually ad%ust timing plans
• Tells neig!(oring %urisdictions #!at is
!appening up0 or do#n0stream from t!em
• Allo#s operations personnel to select t!e
proper response
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&SATMS
• >oal is to en!ance local control
• =ntent is to continue to use existing signal
control !ard#are / soft#are
– ?o#ers initial cost
– Allo#s 6coordination7 of independent net#or's
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&SATMS
• ?imitation is t!at existing competing
vendor !ard#are #on4t tal' to eac! ot!er
• &eeds 6translator7 protocol
• =n future &CT=$ protocol
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CurrentSignal
5ard#are
Translator
$rogram &SATMS
Future
Signal
5ard#are
&SATMS &TC=$ $rotocol
&TC=$
$rotocol
$roprietary
$rotocol
Current &SATMS Design
Future &SATMS Design
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,5OD.S and ,T0T,ACS
• Modern signal control algorit!ms t!at
depend on more detailed sensor output
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Arterial Control
• @ey -uestions are*
– !at data do you !ave
– !en do you !ave it
– !at control options do you !ave
– "ecause t!is determines t!e 'inds of analysisyou can do
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"arriers
• Tec!nical
– ?ac' of communications
– ?ac' of surveillance
– Old underpo#ered proprietary infrastructure
– Cost
– ?ac' of personnel to operate / optimi+e controlalgorit!ms / strategies
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"arriers
• Organi+ational / =nstitutional
– $olitical (arriers
– $roprietary !ard#are / soft#are from vendors
– !o controls t!e system
– Does t!e expertise exist to install operate and
maintain t!e system – Financial priorities
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"arriers
• $olitical
– !at movements are optimi+ed
• Minimi+ed delay / stops not al#ays t!e prime goal
– ?ocal control versus 6regional7 control
– ?o# (id pu(lic contracts and vendor control
issues
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"arriers
• Financial – Most agencies are 6poor7– Value of the system's benefits versus
– Cost of the system
• =nterconnect is expensive
• &e# 8capa(le< !ard#are is expensive• Must compete #it! ne# pavement and
re!a(ilitation
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"arriers
• Training
– Staff 'no#ledge 8(ac'grounds<
• Communications
• Computing
• &et#or'ing
• Statistics
• Soft#are
– Staff ,etention
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"arriers
• Consultant support
– Timing
– Cost
– ,elia(ility
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=ntegration
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!y =ntegration
• S!ared infrastructure can reduce costs
• Avoid duplication of infrastructure
• Allo#s 'no#ledge of conditions outside of
your control (oundaries
• =t increases t!e data/information availa(le
for operational controls
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!at duplication
• .xamples*
– Toll tags – one tag for multiple toll roads
– Surveillance e-uipment
– Communications – T#o different in0ve!iclecomponents can s!are one off0ve!icle
communication system
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=ntegration
Component integration
Bersus
System integration
8Similar (ut different<
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Control System =ntegration
• T#o important aspects of integration
– Tec!nical integration
– Administrative integration
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Tec!nical =ntegration
• Allo#ing independent components to #or'
toget!er*
– .:g: Stereo system components
• 5ard#are connections
• Soft#are connection
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Tec!nical =ntegration
• "iggest issue is standardi+ation
– &e# tec!nology
– .xisting tec!nology
• &ational Arc!itecture
– $!ysical layer
– ?ogical ?ayer
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Tec!nical =ntegration
• $!ysical layer
– Standardi+ed !ard#are connections• $lugs
• Ca(les
• Communication inputs
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Tec!nical =ntegration
• Soft#are
– Data transfer protocols
– Transfer speed
– Data transmitted
• Content• Format
• 1nits
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Administrative =ntegration
=ssues
• Do = really #ant to s!are #it! 6t!em7
• !o pays for #!at
• !o is responsi(le for #!at
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Administrative =ntegration
• !at type of integration
– S!ared control
– S!ared data
– S!ared infrastructure
• Communications
• S!ared components 8tags<
• T!is drives #illingness to participate
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Administrative =ntegration
Decision is (ased on (enefits versus cost
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Administrative =ntegration 0
=ssues• Do = #ant to
– !at do = get
– 5o# muc! does it cost – !at control do = !ave
• =s my system dependent on someone else
• =s my system effected (y t!eirs
– $rivacy• System operator
• 1ser
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Administrative =ntegration
• "enefits
– >ood #ill
– Cost reduction
– &e# data
– &e# capa(ilities
– 5appier user
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Administrative =ntegration
• Costs
– .xtra infrastructure
– Added functionality may lead to less t!an
optimum component features for your original purpose
– $urc!asing limitations
– Added complexity to t!e original system – ?oss of control
– Customer reaction
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Administrative =ntegration
• Control
– T!e more critical to your goal t!e less li'ely
you are to let ot!ers control t!e system
– ,elia(ility
– ,esponse time to pro(lems – Control decisions
– Cost versus responsi(ility
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Administrative =ntegration
• $rivacy
– 1ser information
– Company information
– Freedom of =nformation act
• Balue of data versus cost of data
• Does access to data limit participation
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Administrative =ntegration
Agencies agree to integration #!en
– T!ey see more (enefit t!an cost
– !en t!e cost is #it!in t!eir availa(le (udget