In the United States, "highway speed" typically refers to the legal speed limits set by individual states for highways and freeways. The specific speed limits can vary from state to state and even within different sections of a state. However, the common range for highway speeds is usually between 55 miles per hour (88 kilometers per hour) and 75 miles per hour (120 kilometers per hour).
It's important to note that these speed limits can vary, and it's necessary to observe and adhere to the posted speed limit signs when driving on highways or freeways. Always check local regulations and pay attention to any posted speed limits to ensure safe and legal driving.