When it comes to diesel air quality standards, one thing is clear, or will be as clear as the air is intended to be under the Environmental Protection Agency's Tier 4 emissions standards: If you think EPA is tough, wait until you see what some states and locali-ties are intending to do to add further regulations.
"The responsibility for reducing diesel emissions is moving more toward owners and operators rath-er than manufacturers," the Diesel Technology Forum reported in a 2011 white paper. "Historically, reducing emissions from diesel engines and machines has been totally an issue between engine makers and EPA regulators, where new clean air standards were set and manufacturers made design changes to meet the standards.
"Owners and operators simply purchased the new model engines and equipment, and over time, newer engines replace older ones and the overall emissions levels improve as the fleet gets newer. However, this trend is changing."