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HPMS & Traffic Data

Session 4
November 16, 2011
2011 Highway Information Seminar

 

Traffic Data – Basic Engineering Information

• Uses of State based HPMS Traffic Data
  • Sampling
  • Apportionment
  • Travel Modeling
  • Funding Sources
  • Statistical Analysis
  • Legislation
  • Research

 

 

 

Traffic Data (cont’d)

• Guidance to be discussed:
  • Traffic Counts (Volume)
  • Vehicle Classification
    • Car, Truck etc.
  • Metadata
  • Other Sources of Traffic Data Guidance

 

Traffic Count (Volume) Data

• Required for all Federally Aided Roads (Full Extent)
• Minimum 3-yr count cycle for Principal Arterial System (PAS) and HPMS Sample Sections
• Minimum 6-yr count cycle for other sections, including Minor Arterials , Collectors, & Ramps
• 48 Hour Minimum Duration Required (Fed – Aid Routes)

 

Traffic Count (Volume) Data (cont’d)

• Use adjustment factors to estimate AADT when necessary
• Use growth factors to estimate AADT when measured values are unavailable
• Rounding of AADTs per AASHTO Guidelines is acceptable, but not encouraged

 

Traffic Count (Volume) Data (cont’d)

• Use the following to estimate VMT for non Federal-Aid roads:
  • Current traffic growth rates on collectors and higher systems
  • Limited sample of short term counts
  • Combination of sample and estimated counts
  • Area-wide average daily traffic counts
  • Railroad Crossing Counts

 

AADT Volume Groups
 

Volume Group AADT Ranges 1 Under 500 2 500 to 1,999 3 2,000 to 4,999 4 5,000 to 9,999 5 10,000 to 19,999 6 20,000 to 34,999 7 35,000 to 54,999 8 55,000 to 84,999 9 85,000 to 124,999 10 125,000 to 174,999 11 175,000 to 249,999 12 250,000 and more

AADT data is stratified into 12 volume groups Used for all sampled functional systems Stratification is used for expanding sample data items based on AADT ranges

 

 

Ramp Counts

• Grade-separated ramps only
  • All Federal-aid highways
• Why are ramp counts needed?
  • Many interchange bottlenecks
  • Large amounts of Federal funds spent
  • No Federal data on ramps
• First year: count or estimate
• Minimum of 1 count every 6 years

 

Estimating Ramp AADT

• Factor counts
  • Use nearby ATRs
    • e.g., anchor points for ramp balancing
  • Use factors for either mainline
    • e.g., road with the predominant flow
• Ramps with no counts
  • Traffic matrix estimation
  • Compare turning movement estimation

 

Vehicle Classification Data

• Vehicle Classification Data is used to:
  • Provide accurate percentage of truck traffic
  • Develop seasonal and day of week vehicle classifications
  • Analyze impact of trucks on pavement deterioration

 

Vehicle Classification Data (cont’d)

• Collect data that represents all functional systems
• Observe same count cycles as those for volume data
• Report data that represents HPMS reporting year

 

Vehicle Classification Data (cont’d)

• Collect data for all lanes in both directions
• Ensure axle class algorithm used is consistent among equipment and vendors
• Develop axle correction factors for all seasons
• Use adjusted raw count data which reasonably represents truck travel patterns

 

 

Summary Travel Data

• Vehicle miles of travel (VMT) – Percent
  • Rural minor collector & local
  • Small urban – local
  • Urbanized areas – local
• Travel data by vehicle type
  • 6 functional systems
  • 6 vehicle types

 

 

 

Metadata (traffic)

Year of Record Ex. 2009 State Code Ex. 39 Metadata Type AADT_Pct_Actua AADT_24 AADT_48 AADT_Season AADT_Week AADT_Axle AADT_Growth Class_Pct_Actual Class_24 Class_48 Class_Season Class_Week Class_Growth Travel_Source Travel_Volume_Type Travel_Class Type Travel_QA	Functional System i.e. 1, 2, 3, 4, 5, 6, 7 Rural/Urban Designation State Owned Metadata Item Value See Field Manual Table 3.22 Numeric value associated with the metadata reported See Field Manual Table 3.22

 

 

 

 

 

 

 

Additional Sources of Traffic Data Guidelines

• AASHTO Guide
• ASTM International Standards
  • E1318-09 — WIM systems User
    • Reqts. & Test Methods
  • E1957-04(2010) — Std. Practice
    • using Pneumatic Tubing
  • E2300-09 — Std. spec. Highway
    • Traffic Monitoring Devices

 

Additional Sources of Traffic Data Guidelines, cont’d

• ASTM International Standards, cont’d
  • E2415-05 – Installing Piezoelectric
    • Highway Traffic Sensors
  • E2467-05 — Developing Axle Count
    • Adjustment Factors
  • E2532-09 — Evaluating
    • performance of Hwy Traffic Monitoring Devices
  • E2561-07a — Installation of
    • Inductive Loop Detectors
  • E2759-10 — Highway Traffic
    • Monitoring Truth-in-Data

 

Questions ??