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

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

It was found that, while the existing procedure works well for predicting the onset of thaw, the predicted thaw durations were higher than field observations. Deflection tests indicated that the period of minimum strength coincides with the approximate time that thawing is complete.