For the first time, EPA is proposing to require the emissions control systems of large diesel and gasoline highway trucks and buses to be monitored similarly to passenger cars.

EPA's proposed regulation for onboard diagnostic (OBD) systems for large trucks and buses would help ensure that emissions control systems work properly for the useful life of heavy-duty on-road vehicles.
Onboard diagnostic systems, used in passenger vehicles since the mid-1990s, monitor emissions control components, detect need for emission-related repairs, and alert the vehicle's operator of these problems. They also help inform service technicians what problem exists so that it can be repaired properly. The OBD systems for highway trucks would work the same way.
The proposed requirements are part of the Clean Diesel Truck and Bus Program, which officials claim will result in significant reductions of nitrogen oxides, particulate matter, non-methane hydrocarbons, carbon monoxide, sulfur dioxide and air toxics from diesel-powered vehicles.
EPA says these emission reductions will prevent 8,300 premature deaths, more than 9,500 hospitalizations, and 1.5 million lost work days.
The proposal also makes changes to certain existing OBD requirements for smaller highway diesel trucks.
For more information on this action, visit www.epa.gov/obd/regtech/heavy.htm.