Quote: I really don't see what is so hard to understand here. New 56' semi-trailers are not legal on the Interstate system ANYWHERE as far as federal rules go. A very few states will allow them on STATE highways only but AFAIK those are grandfathered trailers built before the Feds mandated length. The reason California or any other jurisdiction for that matter won't write a special permit for anything other than a specialized trailer (those haulers are seen as just a dry van)is because every freight company on the planet would be hauling 60' trailers around on permits.
It's pretty simple 53' max length, 41' max kingpin.
Kevin
California even has a different law for this.. That's why they have a split axle..
Length - Combinations: Combination vehicles coupled together, such as a truck tractor and semi-trailer, or a truck tractor, semi-trailer and trailer, are limited to 65 feet, or 75 feet, or may be unlimited depending on the route. In addition, legal trucks in California must not exceed a kingpin-to-rear-axle (KPRA) length of 40 feet . Truck lengths are illustrated on this web page: "Truck Map Legend": http://www.dot.ca.gov/hq/traffops/trucks/truckmap/truck-legend.pdf. Truck lengths and routes are discussed in more detail in the Caltrans web page: Truck Size & Routes.
That's why they have a split axle.. 
