Oversize permit requirement

Depends on the state. I would say 4' is safe pretty much everywhere. Also this advice is worth exactly what you paid for it.

 

I would concur with your answer.

 

Some states is zero overhang and others it's half the load. Huge variance.

 

This should clear up any confusion

Missouri oversize permits - regulations and information

 

Every state has it's own laws. Also, it may depend on the freight and whether it's divisible. Just by example, here in California, on STAA routes, you are limited to 75' overall length. So if you are running a long setup that's that long by itself, you don't get any overhang at all. My setup is about 74 feet, but if I move the fifth wheel forward I can give myself a little more room for loads like plastic pipe. You are also limited to 2/3rds of the wheelbase, measured from the rear tractor axle to rear trailer axle, mine gives me about 27 feet of legal overhang, but overhang is measured not from the back of the trailer, but from the last point of support. Structural pieces (beams, poles, pipes, etc.) is exempt under 80 feet from the 75 feet thing, but not the overhang. So I can haul pieces up to 80 feet long with no permits whatsoever, so long as I keep the overhang legal. (and I can).

Other states have different rules, measured in different ways. Some may not allow any overhang at all, or very limited, others allow up to certain amounts, so you can let that lumber load, or plastic pipe, hang off a few feet. Others you can't do that, overhang will only be allowed if it's a non divisible load, and must be permitted.

 

Most state rules on overhang are in here.
State oversize permits & escorts information and requirements

 

Note ‘ non divisible ‘ - most states are fairly generous with overhang for non divisible loads.

Also ‘items of structural nature’ - encompasses a broad range of products, if it can’t be shipped as a shorter length, gives a lot of leeway.

Note ‘overall length ‘ - Missouri for example is 90’ - which I quickly reach with the large car. Escort required on 2-lane roads. Though not specified, after running an auto-issue permit, found the escort is not required on the interstate, as yet - the upper limit is still unknown. Unhelpful when trying to quickly price long pieces. Guess I’ll find out one day.

Missouri is also zero overhang on a 53’ without permit.

The links above will give some effective narcoleptic reading material.

Standardization would be great.