Rational System for Rating Wisconsin Bridges for Truck Loads

Quarterly Reports Other Documents Final Report
March 2009
June 2009
September 2009
 See CFIRE 03-05

Primary Investigator

Mike Oliva
University of Wisconsin – Madison
1415 Engineering Drive, 1214 EH
Madison, WI 53706


The State DOT recently revised load limits for highway bridges in Wisconsin to allow heavier trucks, particularly if truckers had additional axles attached to their trucks to spread loads. Most of the companies involved in transporting timber in northern Wisconsin added the required extra axle at substantial cost. Unfortunately the load ratings for bridges on most county highways are set by local officials and may not reflect actual load capacities. Though the truckers added the extra axles many counties still placed load restrictions on essential bridges on local roads. This project will focus on developing guidelines to aid county officials in deciding whether load ratings are needed, evaluate whether selected posted bridges should be posted, and look at defining useable routes for timber haulers. Removal of non-essential load ratings will save the Wisconsin trucking industry many thousands of dollars in fuel costs and reduce truck emissions by shortening haul routes.


The objective of the planned work is to develop guidelines for decision makers in evaluating whether highway bridges need to have truck load limits and what limits are appropriate.

We intend to accomplish the objective by working with the trucking industry in northern Wisconsin, the WisDOT, and County highway officials to clearly identify the problems and possible solutions by working cooperatively.

The trucking industry will participate by helping to accurately categorize and measure the weights of trucks and axle loads. Then we will analyze a representative set of bridge spans to show the effects of those trucks in comparison to the standard types of trucks that are usually used to define a load rating.  The methods and results will be used to provide simple guidelines for decision making.


  1. Categorize the types of trucks used in Wisconsin for hauling timber
  2. Develop a statistical description of truck loading
  3. Select representative trucks to use in analyzing the response of bridges to the truck loads
  4. Simulate the effects on bridges of varying span lengths
  5. Compare the effects caused by timber trucks to that of standard trucks normally used to load rate bridges
  6. Define a set of equivalency tables for use by non-technical personnel in selecting load ratings for bridges

Project Information

  • Duration: 12 months
  • Dates: July 1, 2008 – June 30, 2009
  • Budget: $16,493
  • Student Involvement: One graduate student
  • Modal Orientation: Highway
  • Project ID: CFIRE 02-20
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