OHPI Home > Presentations

Traffic Volume Data Collection

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

Planning/Environment Needs

• Air quality analysis
• Noise studies
• Traffic projections

 

Project Development Needs

• Interchange Justification Reports
• Design
• Maintenance of Traffic Decisions

 

Operations needs

• Traffic signal timing
• HOV operations
• Work zone decisions

 

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

 

 

 

Who wants TVT?

• Automotive industry companies
• Insurance companies
• Financial services
• Retail

 

QUALITY DATA

 

Guidance

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

        

 

Types of Sensors

• In road/on road
  • — Loops
  • — Piezos
  • — Tubes

 

 

Types of Sensors – cont.

• 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

 

Factors Example – DOW

 

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

 

 

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