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A Pain in the Class

What do all these terms have in common – road, street, highway, freeway, tollway, expressway, avenue, lane, parkway, boulevard? For sake of the word count, the list will end there, but each represents titles of routes which are available for vehicular travel. However, none of them mean jack squat when it comes to determining maximum size and weight limitations in Illinois. Those definitions are left to an antiquated five-part classification system to be discussed in this article.

The first point to understand is that routes either marked (numbered) and unmarked (unnumbered) do not determine size and weight laws. Once upon a time there were trails for frontiersmen, horses and buggies and eventually automobile traffic. Smart people decided to mark these routes with numbers. Smarter people found a way to logically codify them for mapping.

In 1926, the U.S. Route, or U.S. Highway marking system began. These marked roads still exist today, but the mere fact it is classified with a U.S. Route designation does not determine maximum size and weight limits in Illinois.

In 1956, President Eisenhower launched the Interstate highway system. These marked roads are still the primary federal-aid highways in the nation. While their importance is paramount, the mere fact they are classified as an “interstate” does not determine maximum size and weight in Illinois.

Illinois provides counties the ability to mark county roads with numbers. But those title and markings do not determine maximum size and weight laws in Illinois.

Before a reader with extensive knowledge of highway history lore gets their panties in a bunch, yes, there are federal mandates and rules regarding how states set size and weight limits on certain highways. That is irrelevant to this conversation though.

No matter the marking, the funding mechanism or the hierarchy of government ownership ascribed to a particular highway, all routes within Illinois fall into one of five classes. These classifications determine the maximum size and weight limits in Illinois.

Where do you find a map or classification of these highways? The best and most up-to-date resource is the Illinois Department of Transportation website, Here you can layer maps to see what the highway classification is and whether or not the route is state or locally maintained.

The five-part classification system in Illinois used to have a more profound effect prior to 2010 when Illinois had a bifurcated weight system. Today, with all highways in Illinois being uniform in weight, the five-part classification system is more about dimensions than weight.

So what are the classifications? Glad you asked:

Class-I designated highways All interstates and tollways in Illinois are Class I highways. There are a few other Class-I state highways, but local roads cannot be designated as Class-I highways. All Class-I highways are marked.

Class-II designated highways These highways may be marked or unmarked, and can be designated by either state or local government. Statutorily speaking, Class-II highways must have minimum lane widths of 11 feet.

Prior to uniform weight laws in Illinois, it was more common to see local government designate certain highways as Class-II routes to allow for higher weight limits into industrial and commercial transportation areas. Today, local Class-II designation is more about providing longer trucks a lawful way to access these destinations.

Class-III designated highways Much like their Class-II cousins, these highways may be marked or unmarked, and may be classified as such by local or state government. The key disparity here is the Illinois Vehicle Code defines them as having lane widths of less than 11 feet. As roads are rebuilt to higher standards for larger vehicles and traffic volume, Class-III highways are rapidly going by way of the dinosaur.

State non-designated highways The Illinois Department of Transportation has a lot of roadway to cover. The bulk of non-designated state routes are unmarked, but there are plenty of marked state highways which are non-designated as well. Vehicles traveling on these state non-designated highways are not afforded the same length as their state designated highway counterpart.

Local non-designated highways These are county, municipal and township highways, except for the those designated as Class-II or III by the local government. Local non-designated highways lesser length limits as compared to state non-designated highways.

Determining highway classification is only half the battle. Learning maximum size and weight laws is an animal all its own. Both IDOT and the ITEA have resources available to help navigate this legalities of operating vehicles upon this maze of highways. Use them…please.

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