Personal cars imported into the US are regulated by the following agencies:

EPA

They regulate auto emissions. Their certification testing procedure ( ICI program) is time consuming and expensive. Most
cars coming from Canada already meet EPA, most euro or asian cars do not.  Which exact standards apply will depend on the make, model, and year of your car, engine type, what country is was built for, and the reason you are importing the car ( sale, personal use, off road etc. ) Some personal cars will be exempt from EPA regulations.

DOT

They regulate safety items such as headlights, seatbelts etc. Their certification procedure ( Registered Importer program) is
for cars that are to be modified to US spec.See Registered Importer page. Like with EPA, the DOT standards that apply will depend on make, model, year, country it was built for and reason you are importing the car.

US CUSTOMS

They enforce EPA and DOT requirements for importing the vehicle at the port of entry.   In addition, Customs may perform an exam on your car to determine its eligibility for import.  Duty on cars is 2.3% of the declared value, but not all imports are dutiable. See Port of Entry page  
R.I. Import Services can advise you on which emissions and safety regulations, if any,  apply to your exact situation.

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