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If you operate a vehicle over 10,001 pounds Gross Vehicle Weight Rating (GVWR) or Gross Combination Weight Rating (GWCR) in a commercial business, then you are considered to be a motor carrier. You do not have to haul freight to be considered a motor carrier. If you are in business then you can be considered a private carrier and subject to the FMCSRs.
If you operate a vehicle that is considered a motor carrier, then you must have your company name and US DOT number displayed on both doors.
The vehicle and trailer must have a Federal inspection and both be properly tagged.
The vehicle must have all safety equipment including a fire extinguisher and safety triangles.
The driver must have a medical card. Note that a CDL license is usually not required until the GVWR or GCWR exceeds 26,000 lbs. The driver is subject to the Hours of Service regulations and must keep a logbook if traveling further than 100 air miles. The vehicle must be inspected daily and a record kept in the vehicle.
You must stop at the weigh stations although they will usually look at you like you are crazy.
As a motor carrier your business must register and obtain a DOT number. You are now subject to audit and must keep the records and driver’s files as required by the FMCSA.
You need to obtain a copy and review the Federal Motor Carrier Safety Regulations. These regulations must be reviewed by each driver and a copy kept in each vehicle. The 10,001 lb. definition can be found in Section 390.5 and applies only to interstate operations. You could be subject to this regulation regardless of your state if you cross state lines.
Even if you do not cross state lines, most states are now enforcing this regulation on all trucks. http://www.speedingticketcentral.com/commercial-motor-vehicle.html