From another thread I visited Truck Lite's web site. They have a very good PDF file on just what is required lighting wise for the US and Canada. It tells you exactly what types of lights and reflectors you need where. Most SUV sized vehicles need nothing more than what they came with from the factory, but if you make changes that bring the width to 6'8" (2032mm) or beyond you need to follow these regulations. In some cases it would be wise to follow them even if the vehicle doesn't meet the truck or trailer definitions.
http://www.truck-lite.com/wcsstore/tl/resources/images/en_US/PDF/LUG.pdf
http://www.truck-lite.com/wcsstore/tl/resources/images/en_US/PDF/LUG.pdf