Each spring, the Ministry of Transportation determines the dates of the thaw period in Quebec for the three thaw zones in the province.
During this period, heavy vehicles operating on the entire road network must reduce their loads, in accordance with the limits imposed by the Regulation respecting the load and dimension standards applicable to road vehicles and combinations of road vehicles.
During the thaw period in Quebec, the road is 30 to 70% more fragile than normal. A single overloaded vehicle can cause significant damage to it. On the other hand, a slight decrease in loads considerably reduces the damage caused to the pavement.
For this reason, load restrictions are imposed on heavy vehicles during thawing periods. In general, 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.