he Horizon I
t remains unclear what are the extent and long-term effects of U.S. Environmental Protection Agency (EPA) efforts
to limit oxides of nitrogen (NOx)—a major source of smog-forming emissions—from school buses and other medium- and heavy-duty commercial vehicles for the first time in over two decades. What is apparent at this point, is that engine and vehicle manufacturers have voiced wide-ranging support of the Cleaner Trucks Initiative. Bus manufacturers said they are eager to invest in alternative-fuel technology and to update diesel technology. Meanwhile, districts are waiting to see what the rulemaking will mean for their fleets. Some districts worry it will force them to obtain new buses, or make expensive retrofits while funds are tight. Others say it may motivate or augment their interest in switching to cleaner fuels, including gasoline and propane. The November 2018 rulemaking announcement came after states had petitioned the federal govern- ment for lower, standardized NOx emissions limits. Bus and truck industry leaders said a uniform national standard provides consis- tency. The new rule is expected to be published in early 2020. “It’s an important milestone
that ensures the next generation of diesel technology remains a competitive choice, bringing the technology even nearer to zero emissions,” said Allen Schaeffer, executive director of the Diesel Technology Forum industry group. He said new technology will
School bus driver David Smartwood fuels one of Horseheads Central School District’s gasoline buses. The New York district is one of many nationwide that have embraced gas over diesel, with an eye toward upgrading to propane.
likely need to be developed to meet new standards, and that diesel has continuously improved in the face of government regulation. “This initiative sets the pace for the next generation of advanced diesel tech- nology,” he added.
It remains to be seen what form
the rule will take and how stringent the reduction requirements will be. To draft the new rule, the EPA is studying nonattainment areas for ozone that are formed by NOx emissions, requests from various states and industry information, including warranties and technol- ogy. The rulemaking follows the introduction of new requirements in 2007 and 2010, that buses install particulate filters and selective cata- lytic reduction (SCR) systems. The current EPA NOx emis-
sions standard is 0.2 grams per brake-horsepower-hour (g/bhp-hr). Once a new standard is developed, bus manufacturers and owners would have a range of technology and fuel options to meet it. Califor- nia has proposed a standard of 0.02 g/bhp-hr, and could install its own state-specific standard if it is unsat- isfied with the national mandate. Meanwhile, both industry and
regulators have said they are look- ing for “real-world” NOx reductions that play-out under actual driving conditions, and advanced testing — to make sure that is the case, which may be part of new mandates. “Many of the technologies [that
are] required to achieve these re- ductions have been in development independent of new regulations, including advanced SCR systems, NOx sensing and control system technologies, as well as onboard diagnostic and telematic systems,” noted Michael Noonan, director of certification and compliance for Navistar and IC Bus. Noonan added that, “We believe
this initiative will take advantage of many of the technological advance- ments the industry has observed over the past decade, while helping to streamline the certification and compliance process.” He said the singular issue that both industry and regulators have
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