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Traffic Volume Data Collection

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Daniel Jenkins, PE
  Office of Highway Policy Information
  November 16, 2011

Planning/Environment Needs

  • Air quality analysis
  • Noise studies
  • Traffic projections

Busy Highway

 

Project Development Needs

  • Interchange Justification Reports
  • Design
  • Maintenance of Traffic Decisions
Clipart: Construction Work Viewing Plans

Highway

 

Operations needs

  • Traffic signal timing
  • HOV operations
  • Work zone decisions

Clipart: Traffic light and Worker Holding Up Stop Sign

 

OHPI Needs

  • HPMS
  • Monthly TVT report

 

TVT Report

  • Data Requirements
    • — ATR data submitted to TMAS by the 20th of the month after the close of the month
    • — TMAS software performs a number of quality checks on data
      • 7 day error
      • 7 zero hour error
      • Adjacent hour error
      • Directional split error

 

Cover of Traffic Volume Trends – July 2010, showing travel up by 0.8% compared to July 2009.

 

Table 5 of the TVT report, showing vehicle mile changes from July 2009 and July 2010 for all States.

 

Who wants TVT?

  • Automotive industry companies
  • Insurance companies
  • Financial services
  • Retail
Clipart: Road Sign - Gas - Exit 45 with images of Marathon, Shell Gas Shell, Chevron, U Fill, Exxon and Amoco Gas Stations Logo

Clipart: Man using calculator

 

QUALITY DATA

Clipart: People seating at conference table

 

Guidance

  • AASHTO Guidelines for traffic data programs
  • Traffic Monitoring Guide (TMG)
  • HPMS field Manual

Screenshot:AASHTO Guidelines for traffic data programs    Traffic Monitoring Guide (TMG)    HPMS field Manual

 

Types of Sensors

  • In road/on road
    • — Loops
    • — Piezos
    • — Tubes
Work placing sensor on road

Road with Sensors

 

 

Types of Sensors – cont.

Four Photos of Sensors
  • Off road
    • — Infrared
    • — Magnetic
    • — Radar
    • — Microwave
    • — Acoustic
    • — Video

 

 

 

 

Factors

  • Seasonal Factors
  • Day of Week Factors
  • Axle Correction Factors
  • Yearly Growth/Reduction Factors

Determining an accurate AADT is very important to a successful program!

 

Factors Example – Seasonal

Line Chart showing Rural Interstate Seasonal Factors from 1998-2002 for each month, and the average.

 

Factors Example – DOW

Line Graph show 2002 Rural Interstate Weekday comparison of Monday through Thursday, and Monday through Friday, for each month.

 

Factors

  • Misusing the DOW factor can lead to a 5% underestimate
  • Misusing the Seasonal factor can lead to a 15% overestimate
  • Do you factor and are you following the TMG or some other method?

 

Problem

  • The DOT did a traffic count on a minor rural collector (Site A) between January 26-28 (Tuesday-Thursday). The total count for three days was 3,600 vehicles. Calculate the AADT for Site A.

 

Solving Problem

  • Locate an ATR on a similar class facility

 

Solving Problem

  • Locate an ATR on a similar class facility
    • — Found a ATR on a rural minor collector in the adjacent county with the following characteristics:
      • 290,800 veh./yr.
      • January traffic- 19,800 veh.

 

Solving Problem

  • Locate an ATR on a similar class facility
    • Found a ATR on a rural minor collector in the adjacent county with the following characteristics:
      • 290,800 veh./yr.
      • January traffic- 19,800 veh.
    • Calculate AADT and MDAT for the ATR site
      • AADT=290,800/365= 797, say 800 vpd
      • MDAT= 19,800/31= 640 vpd

 

Solving Problem

  • Locate an ATR on a similar class facility
    • —Found a ATR on a rural minor collector in the adjacent county with the following characteristics:
      • 290,800 veh./yr.
      • January traffic- 19,800 veh.
    • — Calculate AADT and MDAT for the ATR site
      • AADT=290,800/365= 797, say 800 vpd
      • MDAT= 19,800/31= 640 vpd
    • — Compute monthly correction factor
      • AADT/MADT = 800/640 = 1.25

 

Solving Problem

  • Determine AADT for Site A

 

Solving Problem

  • Determine AADT for Site A
    • — Calculate ADT for site A
      • ADT= 3,600/3= 1,200 vpd

 

Solving Problem

  • Calculate AADT for Site A
    • Calculate ADT for site A
      • ADT= 3,600/3= 1,200 vpd
    • Calculate AADT
      • AADT= 1,200 X 1.25= 1,500 vpd

 

Data-Collect once, use many times

 

Questions?????????????