Frost law

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Frost laws are seasonal restrictions on traffic weight limits and speeds on roadways subject to thaw weakening.

In climates that experience below-freezing temperatures, damage to roads from thaw-weakening have led to many US states, Canadian provinces[1] and other jurisdictions to enact laws that restrict vehicle loads during spring months, when road structures are thawing from above in a manner that limits water from escaping the soil structure, thereby weakening the pavement underpinnings.[2] [3] [4] The US state of Michigan, for example, during the months of March, April and May reduce legal axle weights of vehicles by up to 35%. Some areas also require heavy vehicles to travel a maximum of 35 miles per hour (56 km/h), regardless of the posted limit.[5] Some states allow load increases on roads during the freezing season.[6]

See also[edit]


  1. ^ Canadian Strategic Highway Research Program (C-SHRP) (September 2000), Seasonal Restrictions in Canada and around the World (PDF), C-SHRP Technical Brief #21, Ottawa, Ontario, p. 8, ISBN 1-55187-059-2 
  2. ^ Wisconsin Department of Transportation (2007), Springtime posted roads (state numbered highways only), retrieved 2010-03-28 
  3. ^ 2009 Minnesota Statutes (2009), 169.87 Seasonal Load Restriction; Route Designation., retrieved 2010-03-29 
  4. ^ Transports Quebec (2010), Québec Pavement Story, retrieved 2010-03-21 
  5. ^ Van Buren County Community Center (2010), Seasonal Weight Restrictions, retrieved 2010-03-28 
  6. ^ 2009 Minnesota Statutes (2009), 169.826 Gross Weight Seasonal Increases., retrieved 2010-03-29 

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