Traffic Monitoring Guide

Truck Weight MonitoringSection 5

Objective Identify Truck Weight Users Needs Describe Truck Weight Program Identify Data Collection Issues Describe Truck Weight Data

Reports

Pavement Design / Maintenance Bridge Design / Loading Enforcement Research Taxation & Administration Freight Planning

Data Users

Truck Weight Program Products Components Structure

Products Gross Vehicle Weights (GVW) Axle Load Distribution Equivalent Standard Axle Load

(ESAL) Day-of-Week and Seasonal

Patterns

ProductsRural Interstate Travel

by Vehicle Type (2001)

77

24 61

4

17

89

Traffic Volumes Equivalent 18,000 lb. Axle Load

0

20

40

60

80

100

Pe

rce

nt

COMPARISON OF GROWTH IN VOLUME AND LOADINGS ON THE INTERSTATE SYSTEM

70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 00 020

100

200

300

400

500

600

700

PE

RC

EN

T G

RO

WT

H (

3-Y

EA

R M

OV

ING

AV

ER

AG

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RURALAVERAGE DAILYLOAD

RURALAVERAGE DAILYTRAFFIC

YEARSource: Truck Weight Study and HPMS

Products

Truck Weight Program Components Users Needs

End in Mind 2002 Pavement Design Guide

Resources Federal-aid and construction funds

Locations Available funds

Truck Weight Groups Criteria for groups

Structure of Vehicle Weight Program Continuous Count Program

Short Term Count Program

Continuous Count Program Purpose?

How many?

Locations?

Purpose Temporal distribution

Hourly Day-of-week Seasonal Direction

Axle adjustment factor Freight studies

How many? Supplement ATR program

Truck corridors

Short Term Count Program Purpose?

Segments?

Cycles?

Duration?

Factors?

Purpose? Spatial distribution (geographical)

Comprehensive

Foundation for AADTT

Axle adjustment factors

Segments? Homogeneous truck traffic section

Usually longer than volume segments Not always Between

Intersections Roadways Interchanges

Cycles? Quarterly Yearly 2 Years 3 Years (TMG) TMG (obsolescence )

Durations? 24 Hr 48 Hr (TMG) 72 Hr 7 - days

Types of Weighing Static Weighing Weight-in-Motion

Static Weighing Advantages

Accurate weight and dimensions Permanent scales

Disadvantages Time consuming Safe site Resource intensive

Picture of Static Weighing

Weigh-in-Motion (WIM) Advantages

More vehicle weighed Better coverage Unbiased sample

Disadvantages Higher installation costs Higher equipment and maintenance

costs Fixed locations

WIM Sensor Technology “ Load Cell” – Hydraulic load cells “Bending Plates” – Strain gauge

load cells “Piezo” – Piezo-electric cables /

film / quartz Fiber Optics Capacitance mats / pads / strips Strain gauges on bridge beams

Picture of Load Cell WIM System

Picture of Bending Plate

WIM System

Picture of Piezo-CeramicWIM System

Picture of Capacitance MatWIM System

Picture of Capacitance Strip

WIM System

Picture of Bridge WIM System

With Strain Gauges

WIM Calibration Calibration Issues

Actual vs. WIM Test truck and random truck Auto-calibration and re-calibration

Front Axle Temperature

Reference Materials WIM Handbook ASTM WIM Standard Long Term Pavement Performance

Software and Reports Vehicle Travel information System

(VTRIS) Truck Weight Study (TWS)

VTRIS(Vehicle Travel Information

System)

Windows-based System FoxPro data base (DBF)

Data Base Management System Load / Validate Generate summary file Produce W-Tables Archive and ship data

VTRIS Products

System wide weight and ESAL’s values

Vehicle weight by vehicle class Weight distribution

W-Tables (TWS) W1-Weigh Station Characteristics W2-Comparison of Weighted vs. Counted W3-Average Empty, Loaded, and Cargo

Weights W4-Equivalency Factors W5-Gross Vehicle Weights W6-Overweight Vehicle Report W7-Distribution of Overweight Vehicles

VTRIS Reports: http://apps.fhwa.dot.gov/vtris/vtris.aspx

Summary Truck weight User Needs Truck Weight Program WIM Issues Truck Weight Data Reports