Southeast Michigan Council of Governments

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Southeast Michigan Council of Governments
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Development of a Traffic Count Database for
Travel Model Calibration

• Brian D. Mohr, Li-yang Feng, and Tom Bruff
• Southeast Michigan Council of Governments
• 11th TRB Applications Conference
• Daytona Beach, FL
• May 7, 2007

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Detroit
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SEMCOG Region
Communities 234
Population4.9 million
Licensed drivers3.4 million
Annual VMT49 billion
Miles of road23,000
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Presentation Overview
Count source
Regional traffic count database
Travel model interface
Model validation files
Count source
Count source
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Challenges

• No consistency in count data format
• No central database for storing counts
• No efficient procedure for linking counts with
  model
• No way to determine if counts sufficient for
  validation

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Solutions

• Create regional traffic count database (RTCD)
• Central repository for all counts
• Source of counts for model, other apps
• Create automated procedure for linking counts
  with model
• Use power of GIS (linear referencing)

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RTCD Development Issues

• Transferring data from multiple sources into
  common format
• Michigan Department of Transportation (MDOT)
• Local agencies (counties, cities)
• Developing RTCD database structure
• Coding counts with GIS attributes

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Traffic Count Database System (TCDS)

• Software features
• Web-based, friendly user interface
• Direct uploading from traffic counters
• Logical relational database structure
• Numerous quality control measures
• Provides SEMCOG easy access to counts from all
  seven counties, Detroit

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Importing MDOTs Traffic Count Data

• Challenges
• Understanding MDOTs count program
• Three types of data PTR, ITS, short counts
• Different data format for each type
• Solution MDOT data conversion tool
• Converts all data into common format
• Flags representative PTR, ITS counts

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MDOT Data Conversion Tool
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SEMCOGs Regional Traffic Count Database (RTCD)

• Oracle database with three primary tables
• Count location descriptions
• Counts
• GIS (linear referencing) coding
• Number of records in database
• Locations 28,080
• Counts available for validation 58,750
• Total counts available 342,049

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GIS (Linear Referencing) Coding

• Counts coded with LRS attributes from base map
  (route/milepoint system)
• All SEMCOG transportation data coded
• Counts coded as segments

Every point ( ) on road network represented by
two coordinates route number, milepoint
Every count location ( ) represented
by three coordinates route number, beginning
milepoint, ending milepoint
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Local agency counts (via TCDS)
Regional Traffic Count Database (RTCD)
Other counts
MDOT counts (via conversion Tool)
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Local agency counts (via TCDS)
Regional Traffic Count Database (RTCD)
Travel model interface
Model validation files
Other counts
MDOT counts (via conversion Tool)
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Model Validation File Creator

• Required input
• RTCD tables (locations, counts, GIS info)
• TransCAD link definition table
• Count alignment table
• Desired statistical parameters
• Output data-based or model-based validation file

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Two Types of Model Validation Files

• Data-based
• Links assigned counts wherever possible
• Not a statistically sound validation file
• Model-based (statistical sample)
• Links stratified by geographic area and
  functional class, sample randomly selected
• Only some links will have counts assigned

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Model Validation File Creator
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Model Validation File Creator
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Matching Counts and Links Using Linear Referencing

• Model links also coded with LRS attributes from
  GIS base map
• Allows geographic comparison of count locations
  and model links

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Multiple Counts at Same Location

• Count attributes used to match counts with
  appropriate model links
• Hierarchy of preferred counts developed
• Examples of preferred counts
• Counts taken in same year as model validation
  year
• Directional counts
• Counts with shorter intervals

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Results

• Entire process works successfully
• Already used on 2002, 2005 highway networks in
  current model
• Will be used soon with 2006 counts
• RTCD data used in many transportation
  applications, including web data tool

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www.semcog.org
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Future Initiatives

• Continue to improve count data quality
• Append data from additional sources into RTCD
• Fully automate importing of data into RTCD
• Begin performing model validation with
  statistically generated sample of links

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Keys That Made This Project Successful

• Establishing data formatting consistency
• Effective communication, coordination with local
  agencies and MDOT
• Establishing data quality controls throughout
  process
• Use of GIS (linear referencing)
• Automating tasks wherever possible

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Local agency counts (via TCDS)
SEMCOG website
Data-based validation files
Regional Traffic Count Database (RTCD)
Model Validation File Creator
Other counts
Model-based validation files
MDOT counts (via conversion tool)
Other transportation applications
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Development of a Traffic Count Database for
Travel Model Calibration

• Brian D. Mohr, Li-yang Feng, and Tom Bruff
• Southeast Michigan Council of Governments
• 11th TRB Applications Conference
• Daytona Beach, FL
• May 7, 2007