FILTERS SOLVE THE PROBLEM
The good news is that technology available today can nearly eliminate diesel particulate matter (PM) and black carbon emissions from older diesels, positively impacting public health and the climate while creating and sustaining jobs in all 50 states. Pictured here is a diesel particulate filter (DPF), which is verified by EPA to remove at least 90% of the PM diesel pollution from the tailpipe.
Diesel particulate filters (DPFs) are installed in place of a traditional muffler, and are verified by EPA to reduce diesel by at least 90%. Pictured below, the comparison of PM pollution from two nearly identical wheel loaders shows the benefit of a diesel particulate filter retrofit (left without filter, right with filter). See this and related videos here.
These filters physically capture soot particles from exhaust, eliminating the black smoke that one typically sees escaping the tailpipe. This photo (right) shows the honeycomb interior of a DPF that traps harmful particles, virtually eliminating emissions. 
Recent federal regulations require these filters in all newly manufactured on-road and off-road diesel engines, but not in the millions of engines already in use that dominate the fleets, and which could operate for decades to come. Retrofitting diesel engines with tailpipe filters can provide immediate reductions in pollution exposure as well as near-term climate benefits, complementing long-term efforts to reduce CO2 emissions.
ANTI-IDLING -- Saving Money and Reducing Emissions
Turning off a diesel engine when not actively working saves fuel and money, while reducing pollution and associated health risks. Dozens of state, county and city policies have been adopted. Click here for ATRI’s January 2010 summary. Automatic shut-off devices are available to ensure that anti-idling policies are followed.
ENGINE RETROFITS
Closed Crankcase Ventilation System (CCV) -- Studies have observed fine and ultrafine PM pollution levels up to 10 times higher inside a school bus than outside, due in part to particulate matter exhaust vented from the engine. A CCV eliminates in-cabin accumulation of diesel particulate matter emissions that can come in through the windows and doors of a front-engine diesel vehicle. A CCV re-routes these toxic crankcase emissions to the tailpipe and filter, so that they are not released to the air near the front door of the bus. This technology is an important piece of reducing driver and passenger exposure for front-engine vehicles.
Engine Rebuild -- To rebuild an engine means that you disassemble and reassemble an engine, replacing some parts. During this process upgrades can be made to reduce pollution.
Engine Repower -- An Engine Repower refers to the removal of an existing engine and its replacement with a newer or cleaner engine. An engine repower not only improves emissions, but it also prolongs the usable life of the vehicle.
RESOURCES
