A vehicle not originally built to U.S. specifications can, under certain circumstances be imported through a registered importer or independent commercial importer, who modifies the vehicle to comply with US equipment and safety regulations and then certifies it as compliant. In practice, this avenue is nearly impossible, even for Bill Gates. Those who import nonconforming motor vehicles sometimes bring in more than one car at a time to spread the substantial cost of the necessary destructive testing, modification, and safety certification. Destructive crash testing is not always needed if the vehicle can be shown to be substantially similar to a model sold in the U.S.