[Code of Federal Regulations]
[Title 40, Volume 18]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR93.124]

[Page 569-570]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 93--DETERMINING CONFORMITY OF FEDERAL ACTIONS TO STATE OR FEDERAL 
IMPLEMENTATION PLANS--Table of Contents
 
   Subpart A--Conformity to State or Federal Implementation Plans of 
   Transportation Plans, Programs, and Projects Developed, Funded or 
       Approved Under Title 23 U.S.C. or the Federal Transit Laws
 
Sec. 93.124  Using the motor vehicle emissions budget in the applicable 
implementation plan (or implementation plan submission).

    (a) In interpreting an applicable implementation plan (or 
implementation plan submission) with respect to its motor vehicle 
emissions budget(s), the MPO and DOT may not infer additions to the 
budget(s) that are not explicitly intended by the implementation plan 
(or submission). Unless the implementation plan explicitly quantifies 
the

[[Page 570]]

amount by which motor vehicle emissions could be higher while still 
allowing a demonstration of compliance with the milestone, attainment, 
or maintenance requirement and explicitly states an intent that some or 
all of this additional amount should be available to the MPO and DOT in 
the emissions budget for conformity purposes, the MPO may not interpret 
the budget to be higher than the implementation plan's estimate of 
future emissions. This applies in particular to applicable 
implementation plans (or submissions) which demonstrate that after 
implementation of control measures in the implementation plan:
    (1) Emissions from all sources will be less than the total emissions 
that would be consistent with a required demonstration of an emissions 
reduction milestone;
    (2) Emissions from all sources will result in achieving attainment 
prior to the attainment deadline and/or ambient concentrations in the 
attainment deadline year will be lower than needed to demonstrate 
attainment; or
    (3) Emissions will be lower than needed to provide for continued 
maintenance.
    (b) If an applicable implementation plan submitted before November 
24, 1993, demonstrates that emissions from all sources will be less than 
the total emissions that would be consistent with attainment and 
quantifies that ``safety margin,'' the State may submit an 
implementation plan revision which assigns some or all of this safety 
margin to highway and transit mobile sources for the purposes of 
conformity. Such an implementation plan revision, once it is endorsed by 
the Governor and has been subject to a public hearing, may be used for 
the purposes of transportation conformity before it is approved by EPA.
    (c) A conformity demonstration shall not trade emissions among 
budgets which the applicable implementation plan (or implementation plan 
submission) allocates for different pollutants or precursors, or among 
budgets allocated to motor vehicles and other sources, unless the 
implementation plan establishes appropriate mechanisms for such trades.
    (d) If the applicable implementation plan (or implementation plan 
submission) estimates future emissions by geographic subarea of the 
nonattainment area, the MPO and DOT are not required to consider this to 
establish subarea budgets, unless the applicable implementation plan (or 
implementation plan submission) explicitly indicates an intent to create 
such subarea budgets for the purposes of conformity.
    (e) If a nonattainment area includes more than one MPO, the 
implementation plan may establish motor vehicle emissions budgets for 
each MPO, or else the MPOs must collectively make a conformity 
determination for the entire nonattainment area.