Super Dumps dump trucks
Just 1 ton of payload can mean over $100,000 over the life of your truck.
Bridge Laws / Weight Laws » Iowa
Map Weight Laws Bridge Laws in AlabamaWeight Laws Bridge Laws in AlaskaWeight Laws Bridge Laws in ArizonaWeight Laws Bridge Laws in ArkansasWeight Laws Bridge Laws in CaliforniaWeight Laws Bridge Laws in ColoradoWeight Laws Bridge Laws in ConnecticutWeight Laws Bridge Laws in DelawareWeight Laws Bridge Laws in Washington D.C.Weight Laws Bridge Laws in FloridaWeight Laws Bridge Laws in GeorgiaWeight Laws Bridge Laws in HawaiiWeight Laws Bridge Laws in IdahoWeight Laws Bridge Laws in IllinoisWeight Laws Bridge Laws in IndianaWeight Laws Bridge Laws in IowaWeight Laws Bridge Laws in KansasWeight Laws Bridge Laws in KentuckyWeight Laws Bridge Laws in LouisianaWeight Laws Bridge Laws in MaineWeight Laws Bridge Laws in MarylandWeight Laws Bridge Laws in MassachusettsWeight Laws Bridge Laws in MichiganWeight Laws Bridge Laws in MinnesotaWeight Laws Bridge Laws in MississippiWeight Laws Bridge Laws in MissouriWeight Laws Bridge Laws in MontanaWeight Laws Bridge Laws in NebraskaWeight Laws Bridge Laws in NevadaWeight Laws Bridge Laws in New HampshireWeight Laws Bridge Laws in New JerseyWeight Laws Bridge Laws in New MexicoWeight Laws Bridge Laws in New YorkWeight Laws Bridge Laws in North CarolinaWeight Laws Bridge Laws in North DakotaWeight Laws Bridge Laws in OhioWeight Laws Bridge Laws in OklahomaWeight Laws Bridge Laws in OregonWeight Laws Bridge Laws in PennsylvaniaWeight Laws Bridge Laws in Rhode IslandWeight Laws Bridge Laws in South CarolinaWeight Laws Bridge Laws in South DakotaWeight Laws Bridge Laws in TennesseeWeight Laws Bridge Laws in TexasWeight Laws Bridge Laws in UtahWeight Laws Bridge Laws in VermontWeight Laws Bridge Laws in VirginiaWeight Laws Bridge Laws in WashingtonWeight Laws Bridge Laws in West VirginiaWeight Laws Bridge Laws in WisconsinWeight Laws Bridge Laws in Wyoming

Federal regulations limit vehicle size and weight on federal highways. This includes all interstate highways across the country, as well as other federal roads designated within the National Highway System or National Network.

Vehicle Weight Limits

Federal weight limits of vehicles and axle loading limits are governed by the Federal Bridge Law (FBL), which has four primary rules:

  1. The maximum weight allowed on a single axle is 20,000 lbs
  2. The maximum total weight allowed on any two consecutive axles spaced eight or fewer feet apart (like tandem axles) is 34,000 lbs
  3. The maximum allowed Gross Vehicle Weight (GVW), or the maximum allowed total weight on any group of consecutive axles on a vehicle, is determined by the Federal Bridge Formula (FBF).
  4. The maximum Gross Vehicle Weight (GVW) on Interstate highways is 80,000 lbs, even when the result of the formula is greater.

The Federal Bridge Formula (FBF)

W = [ ( (LN) / (N - 1) ) + 12N + 36 ]

Where:
  • W = the maximum allowed total weight in pounds for all axles in the group (rounded to the nearest 500 lbs, and rounding down when right in the middle - i.e. 62,250 lbs rounds to 62,000, while 62,300 lbs rounds to 62,500)
  • L = the length or distance in feet (rounded to the nearest foot) from the center of the forward-most axle in the group to the center of the rear-most axle in the group
  • N = the total number of axles in the group

Essentially, the Federal Bridge Formula allows a vehicle to weigh more when there are more axles and/or there is more distance to spread its weight out.

The Federal Bridge Table

For convenience, the Federal Highway Administration published the Federal Bridge Table, which allows one to quickly lookup the federal maximum gross weight on a vehicle or group of consecutive axles, based on number of axles and overall axle length:
Federal Bridge Table Thumbnail

Federal Bridge Law Examples

Bridge law example: tandem dump truck with 215 inch wheelbase and 51,000 lbs GVW
Max GVW: 51,000 LBS
215 IN
Example 1: This tandem dump truck has 3 axles and with a 215-inch wheelbase its overall axle length is 20 feet. So according to the Federal Bridge Formula, its total weight (GVW) is limited to 51,000 lbs.
Bridge law example: quad-axle dump truck with 215 inch wheelbase and 60,500 lbs GVW
Max GVW: 60,500 LBS
215 IN
Example 2: This truck has the same wheelbase and overall axle length as the truck in Example 1, but we've added two axles to make it a quad-axle dump truck with five total axles, which increases its maximum allowed GVW to 60,500 lbs.
Bridge law example: quad-axle dump truck with 250 inch wheelbase and 62,500 lbs GVW
Max GVW: 62,500 LBS
250 IN
Example 3: Here, we took the quad-axle dump truck from Example 2 and stretched its wheelbase to 250 inches, making its overall axle length 23 feet. This has increased its maximum allowed GVW to 62,500 lbs under the Federal Bridge Law.
Bridge law example: 7-axle super dump truck with 250 inch wheelbase and 80,000 lbs GVW
Max GVW: 80,000 LBS
250 IN
Example 4: This is a 7-axle Super Dump, with the truck having the same 250-inch wheelbase as in Example 3. With the Super Dump, when the trailing axle is deployed, the overall axle length is increased by an additional 12 feet, for 35 feet total, and the maximum allowed GVW is increased to 80,500 lbs by the Federal Bridge Formula (80,000 lbs is the max allowed on Interstate highways, however).

Vehicle Size Limits

Federal regulations limit vehicle size as follows:

  • Width: The maximum width of a vehicle is limited to 102 inches
  • Length: For straight trucks*, vehicle length is not federally regulated. This regulation is left to the individual states.
  • Height: Vehicle height is not federally regulated. This regulation is left to the individual states.
* Vehicle lengths for trailers, semitrailers, and combination vehicles are federally regulated.

Updated 03/29/2017

Iowa Bridge Laws

Notice: The Federal Bridge Law (FBL) applies to all interstate and federal highways across the nation. Additionally, the majority of states have adopted the Federal Bridge Formula (FBF) to some degree state-wide, in which case we may just refer to the "FBF" or "FBL". Expand the Federal Bridge Law panel above for the info on those federal regulations.

Iowa Vehicle Weight Limits

Quick Summary / Synopsis for Dump Trucks

Iowa has adopted the FBF state-wide

Recommendations

Being a Federal Bridge Formula state (including dump trucks), a 7-axle Super Dump is the best choice in Iowa. With seven total axles, the Super Dump can weigh 80,000 lbs (the Interstate maximum) on a short and maneuverable wheelbase truck. The next best option is a quint / Simple 16, which falls short of the Super Dump by almost six tons.

Examples for Iowa

Bridge law example: quint dump truck with 258 inch wheelbase and 68,500 lbs GVW
Max GVW: 68,500 LBS
258 IN
Example 1: Iowa has adopted the Federal Bridge Formula state-wide, dump trucks included. Here we have a Quint dump truck (aka Simple 16) on a 258-inch wheelbase, with an overall axle length of 24 feet. This truck is limited to a maximum of 68,500 lbs GVW by both the FBF and Iowa weight laws.
Bridge law example: 7-axle super dump truck with 258 inch wheelbase and 80,000 lbs GVW
Max GVW: 80,000 LBS
258 IN
Example 2: A 7-axle Super Dump on the same 258-inch wheelbase truck can carry up to 80,000 lbs by both the FBF and Iowa state laws (80,000 is the maximum allowed on Interstate highways, although the FBF actually calculates to 81,000 lbs for this truck).

Iowa Vehicle Size Limits

Iowa has the following restrictions on vehicle size*:

  • Width: The maximum width of a vehicle is 102 inches
  • Length: The maximum length of a straight truck is 41 feet
  • Height: The maximum height of a vehicle is 13 feet 6 inches
* Vehicle size regulations shown here are filtered for straight dump trucks. While vehicle width and height restrictions tend to be the same for all vehicles, length restrictions typically vary based on the type of vehicle (trailers, semi-trailers, combination vehicles, etc, usually are allowed greater overall length.)

Updated 03/31/2017

DISCLAIMER:

We try to stay accurate and up-to-date with any changes to the state weight laws, specifically as they pertain to dump trucks, utilizing resources from the Federal Highway Association, popular national vehicle weight guides and manuals, and the individual states' government websites and their official statutes. The weight laws within individual states can be complicated, however, especially when special permits, federal law grandfather rights, seasonal stipulations, and so forth are thrown into the mix. Our purpose here is to present each state's weight laws as they pertain to the typical dump truck, doing typical dump truck work, in the most common dump truck circumstances. If you have some special circumstance or scenario with your truck, we encourage you to visit your state's government website directly, or call your state Department of Transportation. Additionally, if you've discovered an error with our presentation of your state's laws, please let us know via our Contact Us Form and we'll make any necessary corrections immediately.