Measure from the front axle, Regulations for 40 states

Measure from the front axle, Regulations for 40 states 1024 677 Sorcha O'Grady

This morning’s update to our Axle Weight Calculator adds the ability to position bodies and equipment relative to the front axle, adds regulations for federal roads in 6 more states in the US, and enhances existing regulations to take tire width into account.

Measure from the front axle

Up to now, the position of a body or equipment – such as a crane – was specified relative to the back of the cab. Now you can choose to take this measurement from the front axle or the back of the cab.

Simply choose your preference in Settings > Preferences:

TruckScience Axle Weight Calculator Preferences. Truck Body position - Back of Cab. Truck Equipment Position - From Frontmost Axle.

These images show the crane’s position relative to the front axle…

TruckScience Axle Weight Calculator Preferences. Crane’s position relative to the front axle

Clicking and dragging the crane highlights the measurement from the front axle, as you go:

TruckScience Axle Weight Calculator Preferences. Crane’s position relative to the front axle. Drag & Drop.

The same is true for a body, whose position may also be specified relative to the front axle now. Note the dimension for front axle to front of body is displayed above the drawing.

TruckScience Axle Weight Calculator Preferences. Body position. Drag & Drop.

Federal regulations for 6 more states!

We have added regulations for Federal roads for 6 more states – Kentucky, Louisiana, Maine, Nebraska, New Mexico and Utah. This brings our coverage up to 40 states, and your configuration is automatically checked for compliance with regulations in up to 5 states at once.

TruckScience Axle Weight Calculator US State Regulations.  Kentucky, Louisiana, Maine, Nebraska, New Mexico and Utah.

We’re working on adding the regulations for Alaska, Arkansas, Hawaii, Mississippi and Nevada now.

Which just leaves District of Columbia, New Hampshire, North Dakota, South Dakota, Rhode Island and Vermont. Let us know if you would like to see regulations for any of these states added as a priority?

Permits For Divisible Loads

Some US states issue permits for divisible loads that are over 80,000 lbs on federally-funded highways.

The Excess Weight Permit in Idaho allows for 105,500 lbs on the National Network. The Extended Weight Permit in Oregon allows for 105,500 lbs on Interstates and Green and Brown Routes. The Extended Weight Permit in Utah allows for 129,000 lbs on the Interstate and Designated routes. The Greater Weight Authorization in Nebraska allows for 95,000 lbs on the Interstate.

New York State allows for several different types of permits on Qualifying and Access Highways. These allow for weights between 97,400 and 107,000 lbs on specific 5 and 6-axle semi-trucks.  These are the Type 1 (F1) Permit, Type 1A (F1) Permit and the Type 7 (F2) Permit.

All of your calculations in the TruckScience Axle Weight Calculator can be validated against any of these permits now.

TruckScience Axle Weight Calculator US State Regulations.

Choose Settings > Dashboard > Regulations Applied, then search for ‘permit’.

Tire Width considered in compliance checks

The compliance checks now take tire width into consideration.

Pusher and tag axles

Tire width limits don’t usually affect axles with dual tires, as there is enough combined tire width so that the axle weight limit is the limiting factor for that axle.  But pusher or tag single axles are often affected by this limit, as they often have single tires.

Federal Government

In the US, the tire width restrictions are usually based on a maximum weight limit per inch of tire width.  The most common limit is the federal limit specified in US Code of Regulations 23 CFR 658.17 (f), which stipulates that states may not limit non-steer tires to less than 500 lbs per inch.

We’ve updated US Federal – Common Size & Weight Regulations in line with this limit.

States which differ

Many states have limits which are higher than the federal limit. We’ve updated these limits in regulations for New York (Federal, State, Federal Permit F1 Type 1, Federal Permit F1 Type 1A, Federal Permit F2 Type 7), California (Federal and State), Washington, Michigan (Federal and State), Pennsylvania, Florida (Some vehicle bodies only), Oregon, Ohio, Minnesota, Indiana, Connecticut, Massachusetts, Wyoming, Oklahoma, Kentucky, Maine, New Mexico, Louisiana and Utah.

Let’s take an example…

In this example, when we apply US Federal Common Size & Weight regulations, the limit for the pusher axle is calculated as 11 (inches of tire width) x 500 (lb per inch) x 2 (tires) = 11,000 lbs.

The red highlighting draws our attention to the fact that the limit has been exceeded.

TruckScience Axle Weight Calculator US State Regulations. Trye Width.

New York Federal regulations stipulate a limit of 800 lbs per inch of tire width.

So if we apply New York regulations, the limit on the pusher increases to 11 x 800 x 2 = 17,600 lbs, and the axle is no longer considered to be overloaded.

TruckScience Axle Weight Calculator US State Regulations. Tire Width.
Florida ‘Table 3’

Florida allows for weight limits based on tire widths to be applied to “dump trucks, concrete mixing trucks, trucks engaged in waste collection and disposal, and fuel oil and gasoline trucks designed and constructed for special type work or use, when operated as a single unit”.

These vehicles can weigh a maximum of 70,000 lbs and the gross weight limit is based on a limit of 605 lbs per inch of tire width. Normal bridge limits do not apply. 

These limits are now applied to a single unit vehicle and Tanker, Dump or Compactor body in TruckScience, when ‘US – Florida Federal’ regulations are selected.

In this example, the gross weight limit of 68,970 lbs is based on 13″ front tires and 11″ wide dual tires in the rear group, times the tire width limit of 605 lbs per inch.

TruckScience Axle Weight Calculator Permissible Weights

Tire Width in Canada

There is a tire width limit of 10 kg per mm of tire width in Canada, similar to the US.  But Canadian MOU Regulations also stipulate minimum tire width. There is a minimum tire width of 445mm for single tires, which reflects the requirement for wide-base single tires in Canada.  Furthermore, there is a minimum tire width of 150 mm for a tire in a dual tire configuration.

The Canadian MOU regulations in the Axle Weight Calculator have been updated to reflect these limits.

Tyre Width in New Zealand

Support has been added for ‘Large’ (355mm – 443mm) and ‘Mega’ (444mm+) tyres in New Zealand, and we now cater for intermediate weight limits for non-steer tyres. When you add an axle with single tyres to a vehicle, the weight limit will be increased as you increase the tyre width.


We’ve organized the program features into separate editions, to better meet the needs of small cash-conscious, and large professional organizations. Existing subscribers have been grandfathered onto a premium edition at a lower price, in recognition of their loyalty. You can see more detail on the available editions on our Pricing page.

Featured Image

The Freightliner truck in the feature image of this post, with a pusher axle and Cormach crane, is courtesy of our valued customer John Meyer, GM at Garden State Engine & Equipment in New York.

What next?

We love to hear your feedback about how our Axle Weight Calculator is benefiting your business. But what we value even more is when you tell us what it’s missing. Please pop open the chat, drop us an email or pick up the phone to tell us what else you’d like to see in the app, or how we can improve on what’s already there.

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