(a) The model year of initial applicability is indicated by the last two digits of the 5-digit group. A section remains in effect for subsequent model years until it is superseded. The number following the hyphen designates what previous section is replaced by a future regulation. For example, § 86.005-1 applies to model year 2005 and later vehicles and engines until it is superseded. Section 86.016-1 takes effect with model year 2016 and continues to apply until it is superseded; § 86.005-1 no longer applies starting with model year 2016, except as specified by § 86.016-1.

(b) If a regulation in this subpart references a section that has been superseded or no longer exists, this should be understood as a reference to the same section for the appropriate model year. For example, if a regulation in this subpart refers to § 86.001-30, it should be taken as a reference to § 86.007-30 or any later version of that section that applies for the appropriate model year. However, this does not apply if the reference to a superseded section specifically states that the older provision applies instead of any updated provisions from the section in effect for the current model year; this occurs most often as part of the transition to new emission standards.

(c) Except where indicated, the language in this subpart applies to both vehicles and engines. In many instances, language referring to engines is enclosed in parentheses and immediately follows the language discussing vehicles.