This may not be the best SE site for this question but I figured there had to be some engineering insight behind it- I've noticed in the western US tractor trailers have much longer hitches, like below, as compared to the east. http://www.capitaltruckbody.ca/images/PupTrailer2009V5009.jpg

It seems whenever I've been west of the Mississippi, most of the large general construction trailers have these extended hitches. The majority of the trailers I've seen up and down the east coast have shorter hitches, like this: https://dealer-cdn.com/media/offshore/IMG_9655.JPG

My apologies if the wording isn't correct, I'm not familiar with the terminology. The hitch length of western trailers seems to be consistently longer than necessary based on what I've seen on the east coast.

Secondary question that seems independent of trailer length as commented already, why do trapezoidal framed trailers with long tongues like this seem so prevalent in the western US:

enter image description here

I'm acutely aware of reason for their design but I'm just confused why I've never seen any like this on the east coast, even with plenty of mines/quarries around.

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    $\begingroup$ Maximum combined length varies by state. The federal government established minimums (but not maximums) for commercial vehicle maximum lengths for reasonable access to the National Network. But the states can limit maximum combined lengths to anything above the federal minimums. These vary from about 65 feet to 80 feet for Semis. Several Western states have grandfathered 57'semitrailers. Texas and Lousianna allow 59', most others west of the Mississippi allow 53'. East of the Mississippi, most states limit to 48'. $\endgroup$ – Phil Sweet Mar 3 at 14:39
  • $\begingroup$ Bridge formulas for loads and axle spacing are also controlled by states, but weirdly, dump bodies are usually exempt from state bridge formula restrictions and are handled with a simpler rule instead. But they would have to comply with federal bridge formula on the National Network. $\endgroup$ – Phil Sweet Mar 3 at 14:51
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    $\begingroup$ @Phill Sweet, your comments are good for an answer. why don't you just compile them into your answer. I would up vote it. $\endgroup$ – kamran Mar 3 at 20:27

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