In most states, economic regulation of intrastate trucking is done through a state regulatory agency similar to the Federal Interstate Commerce Commission. Generally, these agencies regulate carrier routes and rates. All states tax the operation of both intrastate and interstate motor carriers. Many states also have enacted a variety of environmental regulations affecting truck operation, including roadside safety and pollution checks and fuel regulations. Almost all states have adopted Federal Motor Carrier Safety Assistance Program (MCSAP) provisions. This allows federal regulations to have the force of state as well as federal law. It also gives states the ability to monitor compliance of both intrastate and interstate trucks by using a uniform set of safety regulations. Understanding state and federal trucking regulations can be complicated. To help understand and comply with these sometimes complex federal and state trucking regulations, consider joining or using the services of a state trucking association. Additional help can be obtained from state field offices of the U.S. DOT, Federal Highway Administration, and the Office of Motor Carrier Standards. The Motor Carrier Safety Act of 1984 requires that the Secretary of Transportation, in cooperation with the ICC, establish a procedure to determine the safety fitness of all trucks transporting materials across state lines. As a result, a U.S. DOT "satisfactory" rating is required for all interstate trucking operations.