It seems to be related to charging fees for transport for oversized items, or even setting cutoff points for sizes7weights of objects.

***A previous Q: LIMITE

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Jan 13, eng>por, break point > "limite", pro, closed (4), ok, ok ... 4, Oct 7 2005, eng>por, shipping line > cia de transporte aereo/maritimo/ terrestre ...
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***Another Google would confirm that it's about size/weight:

[PDF]
MARJORY DEMARIA
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Ponto importante a ser visto são os custos do transporte marítimo, que são ... (transporte regular), para um peso mínimo por embarque (break point) ...
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*** Some Google refs in EN:

See http://www.sddc.army.mil/sddc/Content/Pub/37789/Chap3.pdf
APPLICATION OF BREAK POINTS
a. The line haul transportation charge for a shipment shall not exceed the charge that would apply by use of the
next greater unit of weight at rate applicable in the next higher rate bracket.
b. The break point represents weights at which the minimum weight in the next higher weight column times the
rate in that weight column, produces a lower charge than the actual weight of the shipment times the applicable rate
in such rate section. To illustrate:
Shipment weighs 3,655 pounds, moving 510 miles. Under Chapter 4, Appendix 4A the rate
would be 3,655 pounds times $27.60 per CWT equals $1,008.78.


http://www.nrel.gov/wind/windpact/turbine_logistics.html
Transportation logistics: In the United States, the transportation system has unique rules, regulations, and oversized permit requirements for each state. A primary constraint on transportation is the ****oversize- load constraint. Of particular concern is the 4.83m (16 ft) height constraint. Shipments taller than 4.83m risk interference with overhead structures and utilities. Excessive heights can cause considerable expenses because local utilities are required to disconnect power, drop and protect the lines, and then reinstall the wires. Overweight permits can also be problematic. In addition to restrictions on the time of day that oversize loads can be moved, specific dates are also prohibited. The dates are state specific but tend to eliminate periods during the spring when the frozen ground is thawing.
The breakpoint dimensions and weights that were identified for each component are summarized in Table 1. Objects with sizes or heights larger than these breakpoints cost significantly more to transport.