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Bridge Laws / Weight Laws » Colorado

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

Colorado 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.

Colorado Vehicle Weight Limits

Quick Summary / Synopsis for Dump Trucks

On state and local roads, Colorado applies its own relatively simple bridge formula:
 W = 1000 (L + 40)
Number of axles are spacing are not considered in the Colorado bridge formula. Like the FBL, individual axles are limited to 20,000 lbs, but Colorado treats tandem axles like two individual axles, and able to carry 40,000 lbs. Colorado's maximum GVW on non-Interstate roads is 85,000 lbs.

Colorado has an overweight permit that allows a truck having a quad axle grouping and a divisible load (like a dump truck) to carry 110,000 lbs as long as no axles exceed the 20,000 lb limit. The permit does NOT apply to Interstate highways.

Recommendations

The permit allows up to 110,000 lbs, but you need at least 6 axles to pull it off, due to the quad axle grouping requirement as well as the individual axle limit. So a quint axle (or Simple 16) dump truck can technically qualify, but it would need to properly distribute the weight to the axles to keep any axle from exceeding 20,000 lbs, which is unlikely. Due to the physics of the dump body located over the tandem drive axles, and pusher axles located between the front steer axle and the tandem drive axles, inevitably these trucks wind up with too much weight on the tandems, while efforts to reduce this weight with the pusher axles' loading result in too little weight on the front steer axle. A 6-axle Super Dump can pull off the weight distribution fairly easily however, because its trailing axle acts as a lever arm that shifts weight from the tandem axles to the front axle. Add in one more pusher axle, making it a 7-axle Super Dump, and weight distribution is even easier (the 3 pusher axles can be 13k pushers).

Want to forgo the overweight permit? Without the permit, you can run 81,000 lbs on a 5-axle Super Dump with a 318-inch wheelbase, by the Colorado bridge formula.

Examples for Colorado

Bridge law example: 5-axle super dump truck with 318 inch wheelbase and 81,000 lbs GVW
Max GVW: 81,000 LBS
318 IN
Example 1: With the Strong Arm trailing axle, this 5-axle Super Dump can weigh up to 81,000 lbs under the Colorado bridge formula - no permit necessary. Add two more pusher axles and it can carry 80,000 lbs on Interstate highways also.
Bridge law example: quint dump truck with 256 inch wheelbase and 110,000 lbs GVW
Max GVW: 110,000 LBS
256 IN
Example 2: PERMIT REQUIRED. Distributing the weight so that no axle exceeds 20,000 lbs is nearly impossible with this truck configuration, however (too much weight on the tandem drive axles). Likely you'll end up having to carry far less than the 110,000 lbs this Colorado overweight permit allows. On the Interstates, this truck is limited to 68,500 lbs.
Bridge law example: 7-axle super dump truck with 256 inch wheelbase and 110,000 lbs GVW
Max GVW: 110,000 LBS
256 IN
Example 3: PERMIT REQUIRED. You need the Colorado overweight permit to weigh 110,000 lbs, and the Super Dump is likely the only way that you'll distribute the weight properly so that you can actually carry this much. The Strong Arm trailing axle works great redistributing weight from the rear to the front, which would be crucial to pulling off this kind of gross weight while maintaining the axle limits. Bonus: this truck can weigh 80,000 lbs on the Interstate.

Colorado Vehicle Size Limits

Colorado 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 45 feet
  • Height: The maximum height of a vehicle is 14 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 04/07/2017

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.

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