Large Freight Vehicles

Large Freight Vehicles-

Heavy trucks or semi’s are the largest trucks allowed on the road.  You know the big rig that you tried to get to honk the horn as you passed or they passed.  They are mostly used for long-haul purposes, often in semi-trailer or B-double configuration.

They do cause a lot of road damage and wear increase very rapidly with the axle weight.  The axle weight is the truck weight divided by the number of axles, but the actual axle weight depends on the position of the load over the axles.  The number of steering axles and the suspension type also influence the amount of the road wear. In many countries with good roads a six-axle truck may have a maximum weight over 50 tonnes (49 long tons; 55 short tons).

Often they are diesel engines with multiple gear transmissions.  It is not uncommon for a semi to have over 8-10 gears with all the low pull gears and high gear ratio for driving on freeways.  This is one of the reasons a special license and training is required to legally be able to drive a semi.  They are often used for long haul transportation of goods.  Some drivers are owner operators while others work for the company that owns the truck.  You can also find teams that do real long haul loads and stay out for weeks at a time.  Once again a multi-billion dollar industry.


Drivers of semi-trailer trucks generally require a Class A commercial driver’s license (Commercial Drivers Licence) to operate any combination vehicles with a combined Gross Vehicle Weight Rating (or GVWR) in excess of 26,000 lb (11,800 kg) if the gross vehicle weight rating (GVWR) of the towed vehicle(s) is in excess of 10,000 lb (4,500 kg). Some states (such as North Dakota) provide exemptions for farmers, allowing non-commercial license holders to operate semis within a certain air-mile radius of their reporting location. State exemptions, however, are only applicable in intrastate commerce; stipulations of the Code of Federal Regulations (CFR) may be applied in interstate commerce. Also a person under the age of 21 cannot operate a commercial vehicle outside the state where the commercial license was issued. This restriction may also be mirrored by certain states in their intrastate regulations. A person must be at least 18 in order to be issued a commercial license.

In addition, some special Endorsements are necessary for certain cargo and vehicle arrangements and types;

  • H – Hazardous Materials (HazMat or HM) – necessary if materials require HM placards.
  • N – Tankers – the driver is acquainted with the unique handling characteristics of liquids tankers.
  • X – Signifies Hazardous Materials and Tanker endorsements, combined.
  • T – Doubles & Triples – the licensee may pull more than one trailer.
  • P – Buses – Any Vehicle designed to transport 16 or more passengers (including the driver).
  • S – School Buses – Any school bus designed to transport 11 or more passengers (including the driver).
  • W – Tow Truck

Some of this was copied from Wikipedia as it was easier then writing it out.

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