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Office of Highway Policy Information

Traffic Monitoring

Truck Weight Study (TWS) & Weigh-in-Motion (WIM)

Highway Information Seminar

Wednesday, November 16, 2011
By: David L. Jones Sr., Transportation Specialist


 

OBJECTIVE

  • Brief History of TWS
  • State Reporting Requirements
  • Traffic Monitoring Guide (TMG) Update
  • WIM System Deployment
  • TWS Status & National Loading Trends
  • Identify Traffic Monitoring Sensor Technology

 

180 Years of Vehicle Weighing

  • 1831 – Thaddeus Fairbanks
  • 1918 – BPRs First Road Test
  • 1934 – Hayden-Cartright Act
  • 1939 – Type A Loadometer
  • 1942 – Strain Gage Load Cell

 

180 Years of Vehicle Weighing

  • 1950 – O.K. Norman
  • 1955 – AASHO Road Test Approved
  • 1971 – TWS Manual
  • 1985 – Traffic Monitoring Guide
  • 201X Traffic Monitoring Guide Update

 

FHWA’s Current Role

  1. Reviews and Approvals
  2. Distribute Line of Credit
  3. Reimburse States
  4. Technical Assistance
  5. Develop Standards
  6. Develop Regulations

 

EXECUTIVE SUMMARY

Table of Contents

Section – Overview of the Traffic Monitoring Guide
Section – Traffic Data Collection Theory and Equipment
Section – Traffic Monitoring Concepts
Section – Traffic Monitoring Program Design
Section – Traffic Monitoring Methodologies
Section – ITS Data Utilization
Section – Metadata for Traffic Data

 

Table of Contents

Section – HPMS Requirements
Section – Compendium of Additional Methodologies
Section Compendium of Data Quality Control Criteria
Compendium of Equipment of Calibration Procedures, Current Practices, and New Procedure
Section – Traffic Monitoring Data Format

 

Traffic Monitoring Guide (TMG) Update

 

Weigh-In-Motion?

  • Process of Measuring Dynamic Tire Forces
  • Using in Pavement Sensors
  • To Estimate a Static Vehicle Weight

 

Truck Weight Study Status

Map of the United States showing an increased level of reporting of truck information.

Source: U.S. Department of Transportation, Federal Highway Administration, Office of Freight Management Operations, Freight Analysis, version 3, 2010.

 

Graph showing Urban and Rural Interstate Stations between 1990 and 2010.

 

Graph showing None Interstate Station Urban and Rural between 1990 and 2010.

 

Graph showing the National Total All Functional Classification between 1990 and 2010

 

Graph showing the comparison of growth in volume and loadings on the rural interstate system.

 

Graph showing the comparison of growth in volume and loadings on the rural interstate system.

 

Rural Interstate Travel by Vehicle Type

Rural Interstate Travel by Vehicle Type – Graph showing use of VTRIS WIM data submitted for the TWS summarized to produce percent traffic verses loading applied by four vehicle classification groups on Rural Interstate System in 2005.

1Equivalent axle loads provide a means of measuring vehicle wear on pavements by relating them to an 80 kilonewton (18,000) pound) single axle load.
2All 2-axle, 4-tire trucks. Includes pickup trucks, panel trucks, vans and other vehicles (such as campers, motor homes, etc.)
3All vehicles on a single frame have either 2 axles and 6 tires or 3 or more axles (including camping and recreational vehicles and motor homes.)

 

Urban Interstate Travel by Vehicle Type

Urban Interstate Travel by Vehicle Type – Graph showing the use of VTRIS WIM data submitted for the TWS summarized to produce percent traffic verses loading applied by four vehicle classification groups on Urban Interstate System in 2005.

1Equivalent axle loads provide a means of measuring vehicle wear on pavements by relating them to an 80 kilonewton (18,000) pound) single axle load.
2All 2-axle, 4-tire trucks. Includes pickup trucks, panel trucks, vans and other vehicles (such as campers, motor homes, etc.)
3All vehicles on a single frame have either 2 axles and 6 tires or 3 or more axles (including camping and recreational vehicles and motor homes.)

 

Distribution of Vehicle Travel by Lane by Vehicle Type

Graph showing the two lane WIM facility distribution travel by three classification group.   This information can be used when determining funding levels for pavement maintenance.  (scheduling resources for lane 1)

 

Freight and loading routes shown on a map of the United States. These routes are of significant interest for economic vitality in the states.

 

Why Weigh?

  • Pavement Design/Maintenance
    Photo of 2 lane paved roadway

 

Why Weigh? (Continued)

  • Bridge Design/Loading
    Photo of a bridge supporting

 

Why Weigh? (Continued)

  • Bridge Design/Loading
    This sample configuration shows that bridges on the Interstate System highways are used by a wide variety of traffic. They are designed to support expected loadings.  The equation in the diagram. The formula shown in the diagram ties allowable weights to the number and spacing of axles. W equals the maximum weight in pounds that can be carried on a group of two or more axles to the nearest 500 pounds. L equals the distance in feet between the outer axles of any two or more consecutive axles. N equal the number of axles being considered.

 

Why Weigh? (Continued)

  • Enforcement
    Left to right: People in an operations center using weigh in motion technologies to enforce size and weight on the highway system; Oregon Trail in Wyoming.

 

Why Weigh? (Continued)

  • Research
    Top to bottom: LTPP Logo; Poster for long-term pavement performance: Slogan: Knowledge into Action...Performance Data for pavement information

 

Why Weigh? (Continued)

  • Taxation & Administration
    PrePass Site Map Showing 157 Operational and 69 Committed Sites

 

Freight Movement

The map shows estimated truck tonnage on the NHS National concern on international competitiveness; productivity; infrastructure demands.

 

Why Weigh in Motion?

  • Traffic Stream
  • Use of the Highway System
    Picture of the use of the highway system

 

A. Define truck weight roadway groups

Graph showing distribution of weight roadway groups

 

A. Define truck weight roadway groups

Rural Urban
Interstate and arterial major through-truck routes Interstate and arterial major through-truck routes
Interstate and arterial major truck routes Interstate and arterial major truck routes
Other roads (e.g., regional agricultural roads) with little through traffic Other roads (e.g., regional agricultural roads) with little through traffic
Interstate and other freeways serving primarily local truck traffic Interstate and other freeways serving primarily local truck traffic
Special cases (e.g., recreational, ports)

 

B. 6 sites/group

Rural Urban
Interstate and arterial major through-truck routes Interstate and arterial major through-truck routes
Interstate and arterial major truck routes Interstate and arterial major truck routes
Other roads (e.g., regional agricultural roads) with little through traffic Other roads (e.g., regional agricultural roads) with little through traffic
Interstate and other freeways serving primarily local truck traffic Interstate and other freeways serving primarily local truck traffic
Special cases (e.g., recreational, ports)

 

C. One continuous WIM within group

Capture day-of-week and seasonal changes within each group
Photo shows examples of truck weight roadway groups.

 

D. Calibrate, Calibrate, Calibrate

Photos showing 3 types of roadways.

WIM’s Future Role

Photo shows examples of truck weight roadway groups.

 

Travel Monitoring Analysis System

  • National estimates of heavy vehicle highway travel on a monthly basis
  • National estimates of axle loadings and highway ton-miles of freight moved each month, and
  • Highway specific estimates of truck volumes and loadings

 

Travel Monitoring Analysis System

  • Traffic Volume Trends
  • GIS
  • Freight Management
  • Safety

"THE EASY BUTTON"

 

THANK YOU !

David L. Jones Sr.
djones@dot.gov