The Division of Planning purchased a Golden River Weigh-in-Motion system. The first assignment was to determine the optimum calibration setting for operating each weigh mat. The second assignment was to determine the sensitivity of the weigh data. The third assignment was to develop appropriate relationships to adjust the dynamic data to equivalent static data.

A series of correlation efforts established the appropriate calibration factor for each weigh mat. Then the mats were installed at a site on I 64 in Shelby County and data were collected for over 1,600 trucks. From these data, it became evident that equations to adjust dynamic loads to equivalent static loads should be developed for individual axle locations on the truck rather than the gross weight as recommended by the manufacturer. The primary reason was that the steering axle's dynamic load was approximately 70 percent of the static axleload. The discrepancy is due to the torque transmitted from the engine to the drive axles which partially lifts the steering axle off the pavement. Therefore, equations were developed for:

  1. Steering Axle
  2. Single Drive Axle
  3. Single Axle on Trailer
  4. Drive Tandem Axles
  5. Trailer Tandem Axles
  6. Drive Tridem Axles
  7. Trailer Tridem Axles

Observations of truck dynamics combined with literature review indicated that dynamic axleloads are affected by:

  1. Engine torque,
  2. Temperature of rigid pavements,
  3. Location of axle on truck,
  4. Pavement roughness rather than pavement type, and
  5. Suspension system between truck frame and axles.

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The contents of this report reflect the views of the author who is responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the University of Kentucky, of the Kentucky Transportation Cabinet, or of the Federal Highway Administration. This paper does not constitute a standard, specification, or regulation. The inclusion of manufacturer names and tradenames are for identification purposes and are not to be considered as endorsements.