New requirements will help ensure that heavy-duty vehicles run as cleanly as possible over their entire life on the road, and contribute to healthier and cleaner air for all Americans, according to an EPA press statement.

On-board diagnostic systems (OBD) have been required on passenger cars since the mid-1990s, and will now be required on heavy-duty vehicles. OBDs monitor emission control systems and detect malfunctions. The system alerts the driver of the problem, enabling a service technician to diagnose and properly repair the problem.

The final rule is part of EPA’s efforts to work with the California Air Resources Board to develop a consistent national heavy-duty OBD program. OBD systems are an important tool for potentially improving air quality by helping states to meet National Ambient Air Quality Standards.