No, of course not. Those citations/references to federal law are simply there because federal law governs that particular issue. Federal law provides for minimum vehicle safety, emissions, fuel efficiency standards and otther requirements for vehicles, for example. It also provides standards for uniformity in certain road signs so that drivers going from one state to another will recognize the signs no matter which state they travel, which again is a matter of safety. Even where the federal government does not impose mandatory requirements it often encourages the states to follow the standards established by the federal government as a requirement for the state to get federal highway money. The laws regarding DUI offenses are one example where the states adopt mimimum federal standard to get that federal money. The states do, of course, control and regulate a substantial part of transportation law that the federal government has nothing to do with.