What can states not govern in relation to trucking operations?

Answer: D — Rates and tariffs

States cannot govern rates and tariffs related to trucking operations because these aspects are primarily regulated at the federal level. The Interstate Commerce Commission, which has authority over the transportation of goods across state lines, ensures uniformity in pricing strategies to prevent a patchwork of different rates and tariffs that could complicate interstate commerce. This federal oversight promotes fairness and competition, maintaining a stable and predictable environment for both carriers and shippers. In contrast, states do have the authority to implement regulations on other operational aspects such as idling regulations, mud flap requirements, and parking on ramps, which can vary based on local conditions and policies. These regulations are focused on areas that are pertinent to preserving safety, public health, and environmental standards.