Idaho Frost Laws, Seasonal Load Weight and Speed Restrictions – 2019


Type of Load Restrictions: This rule states the size, weight or speed limit restrictions the Department may place on the state highway system if the operation of vehicles could cause damage to the road due to climatic or other conditions. Due to conditions, loads will be restricted to one of the following categories in the interests of public safety: (1) Maximum of: legal allowable weight, (2) 16,000 pounds on any axle, (3) 14,000 pounds on any axle, or (4) 12,000 pounds on any axle.

Weight Limits: Normal overweight special permit limits will be suspended on all highways in the area when seasonal load and speed restrictions are imposed.

Weight Limits Based on Tire Sizes: In administering load limits based on tire sizes or width of tires, credit for tubed tires will be based on the manufacturer's width marked on the tire. Tubeless tires will be given credit for the width of the conventional tubed tires which they replace.

Width Limitation on Two Lane Road: A spring breakup weight restriction to less than legal weight automatically also places a restriction on width allowed by special permit to 12 feet 6 inches during the period of the weight restriction.

Speed Restrictions: Sections of highways that are posted for a maximum loads, trucks and buses with a gross weight of 10,000 pounds or more will be restricted to a maximum speed of 30 miles per hour. Restricted speed zones will be marked by a red marker that limits speeds to 30 miles per hour and a yellow marker that indicates that the legal speed may be resumed.

Weight Restrictions. Spring breakup weight restrictions limit the weight imposed on the highway by individual axles rather than the total gross weight of vehicles. Therefore, overweight permits may be issued that exceed legal allowable total gross load for a vehicle combination subject to these conditions:

a. Minimum tire width is 10 inches or larger.

b. Maximum axle weight on single axle having 2 single wheels shall not exceed 10,000 pounds.

c. Maximum axle weight on single axle having 4 or more tires shall not exceed 14,000 pounds.

d. Permits for nonreducible loads only.

Rules Governing Policy During Spring Breakup Season (39.03.14):

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