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Little Green “X”

Last week, an oversize load crossed a bridge in Washington State when it made contact with the structure. The incident was caught on video which shows two vehicles plunge into the water as the structure crumbles. Miraculously, no one was killed in the collapse and only three people were hurt with non-life threatening injuries. It is incidents like these that create an all-out media frenzy on the safety of the nation’s crumbling transportation infrastructure. Illinois is not immune from the scrutiny. Since 2007, the green “X” has been popping up exponentially across the state…and for good reason.

On August 1st, 2007, the I-35 bridge which crossed the Mississippi River in Minneapolis, MN collapsed. Unlike the collapse in Washington State, the Minneapolis tragedy killed 13 and injured another 145 people. Also, a there was not a bridge strike like in Washington. The Minneapolis bridge was just worn out and there was a design flaw which exasperated the problem.

The response was nothing short of incredible. Every state in the union began a campaign to inspect and evaluate the structures for weight ratings and oversize load measurements. At that time, the Illinois Department of Transportation bridge analysis unit already was evaluating structures, but the rate in which they did this was now thrown into high gear.

With a national average of 1-in-9 bridges being labeled as “structurally deficient”, there statistically was more bridges in a poor state of repair that was listed on IDOT charts and maps. IDOT already issued a map listing all the bridges that had restricted weight ratings. Some structures were classified as “legal weight” and notated by a green “X”. Other structures were classified as “ton load” and notated by the same green “X” but enclosed with a green circle.

In 2011, due to an impending automated permit system, cost restraints and the sheer increase of the little green “X”, the paper map was discontinued. IDOT continues to this day to provide a list of restricted structures on their website, but now notates the green “X” on the interactive map at The reality is the paper map was out of date before it ever went to press.

There is a lot of confusion surrounding the green “X”. As stated above, it is more commonly referred to as a “legal weight structure”. When IDOT conducts a bridge analysis and classifies a structure as such, there is a designated signage that is posted on either side of the structure. The sign will read “10 TONS AXLE / 40 TONS GROSS”. Interestingly, for the sake of character space, there is no tandem or bridge formula weight listed. Just maximum gross and axle weights.

The question that arises from enforcement is how to enforce weight limits on these structures. There are really two kinds of legal weight in the Illinois Vehicle Code. There is legal weight that says all vehicles must not exceed 20,000 pounds/single axle, 34,000 pounds/tandem axle, 80,000 pounds/gross, or the federal bridge formula.

But there are also exceptions to legal weight, and the exceptions are considered legal weight as well. This could be a 3-axle garbage truck that is allowed 22,000 pounds/single axle, 40,000 pounds/tandem and 54,000 pounds/gross. All these weights exceed “legal”, but are statutorily legal as well.

Or maybe it is a “shorty dump” or “bomber”…a 5-axle semi registered as an SHV. Under normal circumstances these vehicles, when loaded to their lawful capacity, are actually overweight on gross and the federal bridge formula. However, their status as a SHV now makes them “legal weight”.

Any vehicle legally operating within the weight limits of the IVC, or the exceptions to legal weight, can lawfully cross a legal weight structure, except for tow-trucks. So the next question is “why post a sign that says a truck can only be legal weight? Isn’t that self-evident?”

The signs are there for overweight loads operating on limited continuous operation (LCO) permits. Vehicles operating under this authority can pretty much run will-nilly on State highways, but cannot run overweight on legal weight structures. They are only allowed the posted weight. And if they forget to check the map and the weekly restriction list before each move, it may very well cost them dearly in an overweight citation. Or even worse, damaging or collapsing a crumbling structure. The little green “X” may be worth more green than it seems.

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