Traffic Detection Systems

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Traffic Detection Systems
CEE 320Anne Goodchild
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Outline

1. What are traffic detectors?
2. Traffic detector importance
3. Detector types
4. Use Example

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What Are Traffic Detectors?
Devices that are used for detecting vehicles,
bicycles, and pedestrians
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Traffic Detection Systems Structure
Detector
Processor/Controller
Storage
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Applications

• Monitor conditions
• Reduce congestion
• Control operations
• Signal timing
• Variable speed limits
• Understand system for strategic planning
• Infrastructure development
• Improved management

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Why Is Traffic Detection Important?
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Why Is Traffic Detection Important?
Freeway Monitoring
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Why Is Traffic Detection Important?
Actuated Signal Control
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Why Is Traffic Detection Important?
Ramp Meter Control
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Why Is Traffic Detection Important?
Dynamic Traffic Assignment
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Why Is Traffic Detection Important?
!
!
E-Message Sign
Control Center
Quality Data
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Traffic Detector Types

• Inductive loops
• Video
• Microwave
• Infrared
• Acoustic
• Radar
• Magnetic
• Radio frequency
• Global positioning system (GPS)

Use various waves and fields, frequencies,
passive or active, mobile or fixed infrastructure
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Share of Detector Types at new ATMS Sites
Environment, cost, application
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Popular Traffic Detector Types
Inductive loops
Video Image Processors (VIPs)
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Popular Traffic Detector Types
Remote Traffic Microwave Sensor (RTMS)
Photos and picture from Electronic Integrated
Systems, Inc.
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RTMS

• Multi-zone traffic detector with few occlusion
  problems
• Unaffected by weather and light
• Low-power microwave signal
• Volume, Occupancy, Average Speed and
  Classification by length

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Popular Traffic Detector Types
Magnetic Sensors
Infrared Sensors
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Popular Traffic Detector Types
Radio Frequency Tag
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Popular Traffic Detector Types
ASIM TT 298 Doppler RADAR, ultrasonic, passive
infrared.
Volume, classification, speed, occupancy, queue
detection, wrong-way
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Popular Traffic Detector Types
ASIM TT 298 Doppler RADAR, ultrasonic, passive
infrared.
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Popular Traffic Detector Types
Intersection Control
Traffic Data Acquisition
infrared (counting) ultrasonic (vehicle
height) microwave doppler radar (speed)
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Popular Traffic Detector Types
GPS-Based Tracking Systems
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Inductance Loop Detectors

• Most popular

Photos from Never Fail Loop Systems, Inc.
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Inductance Loop Detectors
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Inductance Loop Detectors
Loop inductance decreases when a car is on top of
it.
Inductance
T ton
0
ton
T toff
toff
Time
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Inductance Loop Detectors
Single loop measurements?

• Single loops can measure
• Occupancy (O) of time loop is occupied per
  interval
• Volume (N) vehicles per interval

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Loop Detector Signatures
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Inductance Loop Detectors
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Inductance Loop Detectors
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Dual Loop Detector

• Formed by two consecutive single loop detectors
  placed a short distance apart

ldist
lloop
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Dual Loop Detectors
ldist
lloop
T t1
T t2

• Dual loop measurements

oti on-time for loop detector i
Measured vehicle lengths are used to classify
vehicles into different categories, such as long
and short.
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Inductance Loop Detectors
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Can We Get Speed from a Single Loop?

• Perhaps

s speed (ft/sec)
EVL effective vehicle length (ft)
to occupancy time (s)
EVL vehicle length detector length
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Can We Get Speed from a Single Loop?

• Using typical traffic data

s speed (miles/hr)
N number of vehicles in the observation interval
T observation interval (s)
O percentage of time the loop is occupied by vehicles during the observation interval (occupancy)
g speed estimation parameter
100 converts percent to decimal
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Inductance Loop Detectors
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Video Image Processors
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Video Image Processors
Much more promising for pedestrian detection.
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A Use Example Ramp Metering
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Ramp Meter Schematic
Diagram from ITS Decision website
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Example SR 520
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What is the Difference?
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Primary References

• Cosgrove, C. and Cutchin, C. (2003). ITS
  Decision. Website hosted by the California
  Center for Innovative Transportation at the
  University of California and Berkeley and
  Caltrans. http//www.calccit.org/itsdecision
• Wang, Y. (2004). CEE 599F, Advanced Traffic
  Detection Systems Course Pak. Civil and
  Environmental Engineering, University of
  Washington.