Environmental regulatory agencies focus on four types of engine emissions: carbon monoxide, hydrocarbons, nitrogen oxides, and particulate matter. As more focus is placed on health and environmental issues, governmental agencies throughout the world are enacting more stringent laws to reduce these emissions.
Because so many diesel engines are used in trucks, the U.S. Environmental Protection Agency and its counterparts in Europe and Japan first focused on setting emissions regulations for the on-road market. While the worldwide regulation of nonroad diesel equipment came later, the pace of cleanup and rate of improvement have been more aggressive for nonroad equipment than for on-road engines. Non-road emissions reductions:
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- Tier 3/Stage III A emissions regulations required a 40 percent reduction in NOx compared to Tier 2/Stage II.
- Interim Tier 4/Stage III B regulations require a 90 percent reduction in PM along with a 50 percent drop in NOx compared to Tier 3/Stage III A.
- Interim Tier 4/Stage III B and Final Tier 4/Stage IV must pass additional emissions tests including the steady-state 8-mode test (ISO 8178) and the rigorous nonroad transient cycle (NRTC) test.
- Final Tier 4/Stage IV regulations, which will be fully implemented by 2015, will maintain levels of PM and require an additional 80% reduction in Nox compared to Interim Tier 4/Stage III B.