Why Do They Use Kilometers in Arizona | NAFTA

Road signs in southern Arizona on the I-10 use kilometers due to a combination of historical factors and international agreements. While the United States primarily uses the Imperial system for measurements, including miles and feet, some specific locations near the U.S.-Mexico border have adopted the metric system for consistency and ease of communication.

One significant reason for this is the proximity to Mexico, where the metric system is the standard. Having consistent units of measurement on both sides of the border simplifies transportation and trade, especially for commercial vehicles that cross the border regularly. Additionally, international agreements, such as the North American Free Trade Agreement (NAFTA), influenced the adoption of metric units in certain areas.