Iowa Spring Thaw Restrictions

What Are Spring Thaw Restrictions?

Every year from roughly March through May, Iowa DOT posts weight restrictions on secondary roads to prevent damage during the spring thaw period. When frozen ground thaws, road subgrades become saturated and soft. Heavy trucks on these roads cause structural damage that costs millions to repair. The restrictions limit axle weights on affected roads until the ground firms up.

Spring thaw restrictions do NOT apply to Interstates (I-80, I-35, I-29) or most US highways. They primarily affect:

• County roads
• Secondary state highways
• Local roads with lighter pavement structures

How the Restriction Map Works

Iowa DOT publishes an annual Spring Restriction Map that shows which roads are restricted, what the weight limits are, and when restrictions are in effect.

Reading the Map

The map is updated regularly as conditions change. A road that is restricted in early March may be cleared by mid-April if conditions improve. Conversely, a late-season freeze-thaw cycle can extend restrictions into May.

Where to Find It

• Iowa DOT website: search for “Spring Restriction Map”
• Contact Iowa DOT Permit Office: 515-237-3264 for current status
• Local county engineer offices for county road specifics

Typical Timeline

The timeline varies year to year based on winter severity and spring temperatures. A warm, dry spring means earlier clearing. A cold, wet spring extends restrictions into late May.

Impact on Trucking Operations

Weight Limits

When a road is posted with spring thaw restrictions, the typical weight limits are:

Posted limits override normal legal weights. Running over a posted restriction is a weight violation with fines calculated on excess weight.

Routing Impacts

• Grain elevators on restricted roads: Harvest carry-over loads and spring grain movements may need to route around restricted county roads to reach elevators
• Livestock hauling: Feedlot and farm access roads may be restricted, requiring alternate routing
• Construction materials: Spring construction season starts when roads are still restricted, creating routing challenges
• Oversize/overweight permits: Permit routes may need to be modified to avoid restricted roads

Planning Strategies

1. Check the restriction map before dispatching — especially for loads going to rural destinations
2. Use Interstates and US highways as much as possible — these are not subject to spring restrictions
3. Contact the county engineer for specific county road conditions — county-level detail is more current than the statewide map
4. Build extra time into schedules — alternate routing around restricted roads adds miles and time
5. Monitor updates — restrictions change as conditions evolve, sometimes weekly

OSOW Permits During Spring Thaw

Oversize/overweight permits are affected during the spring thaw period:

• Permit routes may be modified to avoid restricted roads
• Some permits may be delayed until restrictions are lifted
• Time-sensitive loads should be planned well in advance
• Contact Iowa DOT Permit Office at 515-237-3264 for current permit routing availability

Connection to Agricultural Operations

Spring thaw restrictions coincide with early planting season, creating a conflict for agricultural haulers. Anhydrous ammonia, fertilizer, and seed all need to move to farms just as restrictions tighten on the roads that serve those farms.

The Iowa Agricultural Trucking Guide covers the 25% agricultural weight exception and seasonal freight patterns in detail.

Neighboring State Comparison

Iowa, Minnesota, and Wisconsin share similar spring thaw challenges due to their northern latitude and soil types. Carriers operating across these states should monitor all three restriction programs.

For Iowa trucking insurance during the spring thaw season and beyond, contact RMS at (208) 800-0640.