control of air pollution from new motor vehicles amendments to the tier 2 motor vehicle emission regulations proposed rule 4 pages english . epa is proposing to make minor amendments to the existing tier 2 motor vehicle regulations 65 fr 6698 10 february 2000 hereinafter referred to as the tier 2 rule . these proposed minor amendments are consistent with our intention under the original tier 2 rule to provide interim compliance flexibilities for clean diesels in the passenger car market. while the automotive industry has made rapid advancements in light-duty diesel emissions control technologies and will as a result be able to produce diesel vehicles that can comply with the primary regulatory requirements of the tier 2 program diesel vehicles still face some very limited technological challenges in meeting the full suite of tier 2 requirements. this action would provide two voluntary interim alternative compliance options for a very limited set of standards for oxides of nitrogen nox including only high altitude and high speed high acceleration conditions. these temporary alternative compliance options are designed to be environmentally neutral as manufacturers choosing them would then be required to meet more stringent standards in other aspects of the tier 2 program. the alternative compliance options would last for only three model years during which time advancements in diesel emissions control technologies would be further developed. in the rules and regulations section of this federal register we are making these technical amendments as a direct final rule without prior proposal because we view these technical amendments as non-controversial revisions and anticipate no adverse comment. we have explained our reasons for these technical amendments in the preamble to the direct final rule. if we receive no adverse comment we would not take further action on this proposed rule. if we receive adverse comment we would withdraw the portions of the direct final rule receiving such comment and those portions would not take effect. we would address all public comments in a subsequent final rule based on this proposed rule. we would not institute a second comment period on this action. any parties interested in commenting must do so at this time. the associated direct final rule full text is available online at urls a257.g.akamaitech.net 7 257 2422 01jan20061800 edocket.access.gpo.gov 2006 06-2979.htm a257.g.akamaitech.net 7 257 2422 01jan20061800 edocket.access.gpo.gov 2006 pdf 06-2979.pdf