Each spring, the Ministry of Transport determines the dates of the thaw period in Quebec for the three thaw zones in the province.
During this period, heavy vehicles circulating on the entire road network must reduce their loads, following the limits imposed by the Vehicle Load and Size Limits Regulation.
During the thaw period in Quebec, the road is 30% to 70% more vulnerable than in regular times. A single overloaded vehicle can cause significant damage. On the other hand, a small reduction in loads considerably reduces the risk of damage.
For this reason, load restrictions are imposed on heavy vehicles during the thaw period. Typically, these restrictions range from 8% to 20%.
Following a monitoring of the thaw progress in the pavement, the thaw period is determined. This monitoring is done using probes distributed throughout the Quebec road network. Weather forecasts are also taken into consideration.