ATMS

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ATMS

• Advanced Traffic Management 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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ATMS Requires

• Control mechanism
• Stop lights
• Barriers
• Traveler information?
• How DO you control traffic on a freeway?

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ATMS Requires

• Surveillance function
• Loops
• Cameras
• As data
• As images
• Other
• Radar
• Vehicle probe data

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ATMS Requires

• Communications
• To obtain the surveillance data, and
• Request required control system changes

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ATMS Requires

• Data manipulation
• What exactly do you do with the data you have?
• Decision support systems
• Data fusion
• Using data from multiple sensors

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ATMS Requires

• Control algorithms
• Old
• Time of day
• Fixed volumes
• New
• Adaptive
• Real time volumes
• Predictive (in time or space)

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ATMS Requires

• Maintenance of the system
• Operational systems need a higher level of
  maintenance than simple infrastructure
• Fail safe operational requirements
• How much data is enough?
• 1 of 4 lanes?
• What spacing of detection?)

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ATMS Requires (?)

• Optional functions
• data collection
• storage, and
• performance monitoring / operations planning

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Examples of ATMS

• Freeway systems
• Ramp metering
• Fixed time
• Local adaptive
• System level adaptive control
• Routing
• Adaptive speed control

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Examples of ATMS

• Arterials Control Systems
• Actuated semi-actuated control
• SCOOT
• SCATS
• OPAC
• RT-TRACS
• (NSATMS)
• RHODES

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Examples of ATMS

• Automated toll collection
• Parking systems
• Emergency response

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Ramp Metering

• Objectives
• Reduce conflicts at ramp terminals
• Decrease merge congestion
• Reduce accident rates
• Encourage diversion to/from specific ramps
• Limit total volume on specific freeway segments
  at specific times

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Ramp Metering

• Objective Maintain flow at maximum levels by
• Preventing flow break down
• Increase total hourly throughput by maintaining
  throughput
• Improve speed of incident recovery
• Promote/deny specific movements

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Ramp Metering

• Minimize air pollution emissions and gasoline
  consumption by reducing stop and start movements
• Minimize ramp delays while maintaining mainline
  flow
• Minimize queue spillback onto arterials

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Ramp Metering

• Maximize freeway flow and freeway performance
• is contradictory to
• Minimize ramp queues and ramp delays

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Ramp Metering

• Keys to successful operation
• Know the maximum volume that can use each ramp
• Current local mainline volume
• Future local mainline volume (upstream volume)
• Downstream congestion
• Finding the correct balance between ramp queue
  and freeway delay

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Ramp Metering

• Know the Volume
• Needs surveillance
• On the mainline
• Approaching the merge point
• Upstream of the merge
• Downstream of the merge
• By the stop bar on the ramps
• Queue length
• Advanced queue detection

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Ramp Metering

• Bring the data back to a central point
• This allows decisions to be made given geographic
  areas larger than locally
• Also allows data storage for later review /
  analysis

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Ramp Metering

• Local control
• minimize merge conflict
• Bottleneck algorithm
• maximize ramp queue, given no current downstream
  freeway delay
• Fuzzy Neural Network
• trade off ramp queues against mainline flow
• avoids direct use of volume

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Freeway ATMS Route Control

• Move vehicles to those routes with spare capacity
• Operational concerns
• Are there parallel routes with spare capacity?
• Are there routes (ramps) where merging causes
  less disruption?
• Will the diversion cause more congestion than it
  will relieve?

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Freeway ATMS Route Control

• Route Diversion
• Political concerns - what are the impacts of
  route diversion?
• Are the new routes designed for that traffic?
• Are there concerns about who benefits / loses?
• Do the people/businesses that live along those
  routes object to their use by pass through
  traffic?

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Freeway ATMS Route Control

• Technical How do you cause drivers to divert?
  What route do they take?
• Traveler information (VMS / CMS / HAR / radio)
• Metering (fast versus slow)
• Ramp closures
• New technology (PDA messages)
• Can you manage how many vehicle change routes?
• Many drivers wont change routes

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Surveillance
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Surveillance

• Is necessary to manage traffic
• Without surveillance, there is no knowledge of
  what is occurring

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Surveillance Technologies

• Loops
• Cameras
• Other technologies
• Radar
• Acoustic
• Infrared
• Other

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Inductance Loop
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Loops

• Advantages
• Inexpensive
• Easy to install
• Well known attributes / mechanics
• Provide
• Volume
• Lane occupancy
• Speed (sometimes)
• Vehicle classification

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Loops

• Disadvantages
• Single location (non-movable)
• Subject to pavement failure / degradation
• Not good if channelization is likely to change
• Difficult to collect vehicle classification data
• Dual loops
• Inductance signature recognition

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Cameras

• Two basic technologies
• Video
• Digital image processing

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Pan/Tilt/Zoom Camera
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Cameras

• Conventional video
• Needs a person watching
• Great for short time period
• Poor for longer time periods
• Good for incident verification
• Good for public information
• Not good for routine data collection

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Cameras

• Digital Image Processing
• Reasonably new technology (15 years at a
  reasonable price)
• Several different technologies
• Each with different costs / capabilities

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Cameras

• Autoscope - style
• A US vendor early adopter
• Uses low cost, fixed cameras
• Acts like a digital loop
• Has limitations in bad weather / lighting

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Cameras

• Other digital image processing
• Movable cameras
• Harder to calibrate
• More expensive cameras
• Multi-use cameras
• Vehicle tracking systems
• Travel times
• License plate readers

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Other Technologies

• Radar
• Side fired / Over-head mounted
• Data similar to loops
• A non-intrusive sensor (easier to access)
• Acoustic
• Also a non-intrusive sensor

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Other Technologies

• Infrared
• Both with reflector and without reflector
• Non-intrusive
• Not effected by weather
• Other
• RF for electronic tag reading
• Surface acoustic wave (SAW) for tag reading
• Optical scanners (bar codes)

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Other Technologies

• http//www.nmsu.edu/traffic/
• Summary of Vehicle Detection and Surveillance
  Technologies Used in Intelligent Transportation
  Systems - Detector Handbook (under Whats New)

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Surveillance

• When choosing surveillance system / technology
• Type of data collected
• Cost of data collection
• Accuracy of data collected
• Reliability of equipment
• Frequency of communications
• Flexibility

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Type of Data

• Volume
• Vehicle presence
• Lane occupancy
• Vehicle classification
• Vehicle speed / travel time
• Weight
• ID
• Other (location? status? revenue?)

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Cost of System

• Purchase
• Installation
• Operation
• Maintenance

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Cost

• Purchase price
• Sensor
• Electronics
• Communications
• Software
• License? (How many can you use?)

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Cost

• Installation location effects cost
• In ground
• Below ground
• Pole mounted
• Bridge mounted
• Need for traffic control?
• Communications
• Power
• Cabinets

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Cost

• Operations
• Power
• Communications
• Bandwidth required
• Wireless / wireline
• Frequency of communications
• Staff oversight

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Cost

• Maintenance
• Mean time before failure (life cycle costs)
• Routine maintenance requirements
• External effects
• Bad weather
• Deteriorated pavement conditions
• Replacement parts (sole source?)
• Ease of sensor replacement

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Accuracy

• How important is it?
• Can you accept small errors?
• Volume 5
• Speed 3 mph
• Error in reading Toll tags?
• Classification of truck
• It depends

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Reliability

• What happens if a data point is missing?
• Once
• Frequently
• Consistently but intermittently
• Completely
• Fail safe design
• Graceful failure design

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Reliability

• To get better reliability
• Purchase better equipment (price / warranty)
• Build redundantly
• Buy equipment designed for the environment it
  will be placed in
• Must trade off against cost

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Communications

• How often does data get transmitted from
• Sensor
• Location

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Communications

• Frequency of communications
• Each activation?
• Each second
• 20 seconds
• 5 minutes
• 15 minutes
• Hourly
• Daily

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Communications

• Size of data packet
• Summary statistic
• Raw data
• For example
• Digital image of picture
• Analog image of picture
• Count of cars made from picture
• Count of cars made from 15 minutes of pictures

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Communications

• Must select communications strategy based on
• Control system data need
• Cost of bandwidth
• Installation
• Operation
• Redundancy / reliability