Thawing Index (TI)
TI = (Average Daily Temperature - Reference Temperature)
Varies from 29 degrees F on February 1 to 24 degrees F on March 15
Cumulative Thawing Index
Summation of the Daily Thawing Indices
Based on observations of pavement deflection, frost depth and air temperature at the Mn/ROAD site,
thawing reaches a critical state at a cumulative thawing index of about 25 DegFDays. The criteria used to
begin road restrictions is a cumulative thawing index greater than 25 DegFDays and a weather forecast that
predicts further increases in the thawing index.
The above criteria are based on findings contained in the publication by Van Deusen, Schrader, Worel
and Bullock,1998, "Springtime Thaw Weakening and Load Restrictions in Minnesota, Transportation Research
Record 1615" presented at the 77th Annual Meeting of the Transportation Research Board, Washington, DC.