A study was undertaken to evaluate criteria used to predictwhen to place and remove springtime load restrictions. The objectiveswere to (1) evaluate current springtime load restriction procedures,(2) investigate pavement strength changes in relation to springtimefreeze-thaw events, and (3) suggest a more rational method fordetermining when to remove the load restrictions.

Mn/DOT load restriction placement and removal dates for a tenyear period were tabulated and compared to predictions based onthe existing model. Data collected from eight different flexiblepavement test sections, including falling-weight deflectometer,resistivity probe, and in situ strain gauge data, were used toassess environmental effects on pavement strength.

It was found that, while the existing procedure works wellfor predicting the onset of thaw, the predicted thaw durationswere higher than field observations. Deflection tests indicatedthat the period of minimum strength coincides with the approximatetime that thawing is complete.