Seasonal load restrictions are necessary on specified routes to prevent extensive pavement surface damage. When snow, ice and frozen ground thaw in late winter and early spring, some road beds and base gravel become saturated and their ability to carry truck loads is reduced. The potential for severe highway distress during the freeze-thaw cycles is high. Older highways are more susceptible to frost action than highways constructed to today's standards. To protect Montana highways investment and to keep highways serviceable, load restrictions and speed limits must be placed on vulnerable highways.
The Department of Transportation will place load restrictions for single axle and tandem axle weights and pounds per inch width of tire and speed limits on highways vulnerable to distress. Each District Administrator or Area Maintenance Chief will make a conscientious effort to place load and speed limits only when necessary and lift the limits as soon as possible. Hay grinders and their towing units are exempt from the restrictions of this policy.
In the order of severity, the following types of restrictions to be imposed on Montana highways are:
- On specific routes or sections of highway, between major cities or between major intersections, where the road surfaces for the entire route are adequate to carry legal loads, the District Administrator or the Area Maintenance Chief may place a reduced speed limit on those sections of highway that show distress. If this limitation does not prevent further distress or damage, then more restrictive limitations may be imposed.
- On specific routes or sections of highway, between major cities or between major intersections, where the District Administrator or Area Maintenance Chief determines the road surface is susceptible to damage from heavy loads, load limits will be imposed for the entire section of highway. A load limit of (8 tons single axle and 16 ton tandem axle is a 400 pounds per inch width of tire weight restriction) signs will be posted at the route before the pavement surface starts to deteriorate may defer placement of more restrictive load limits. If the highway continues to show signs of uncontrollable distress under this limitation, the District Administrator or Area Maintenance Chief will impose lower or more restrictive limits.
- On specific routes or sections of highway, between major cities or major intersections, where the District Administrator or the Area Maintenance Chief determines the road surface is particularly susceptible to extensive damage from heavy loads, or where surface damage cannot be controlled by less restrictive limits, then the limitation will be 7 tons single axle and 14 tons tandem axle or a 350 pounds per inch width of tire weight restriction and reduced speed limit will be placed through distressed areas.
It is important for the trucking industry and suppliers of goods and products to cooperate and comply with load restrictions and speed limits. If compliance with less restrictive limits is not found, future more restrictive limits may be imposed.
It is expected that the trucking industry will supplement the enforcement of the load and speed limits by employing radar equipped cars for surveillance of trucks under their jurisdiction. Observed violations from others outside of their organization will be reported to the Department of Transportation. The trucking industry will also give positive instruction to their drivers relative to the load and speed limits. Solicitation is made to all suppliers of all goods and products to do the same.
Department of Transportation personnel will observe truck movement on restricted routes and report any violations of either speed or load limitations to proper authorities.
Excessive violations may lead to the implementation of more restrictive limits.
This policy supersedes all previous policies on load and speed limits.