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Off-Model Analysis

Air Quality analysis methodologies have become more refined over the years to fill the need in the transportation community to satisfy various requirements including Transportation Conformity and Congestion Mitigation and Air Quality Program project justification. Off-Model methods have been developed and refined to allow for analysis of innovative, as well as some common, projects to account for reductions in vehicular emissions. The most typical analysis is associated with Vehicle Miles of Travel (VMT) reductions, but reductions in emissions also can occur due to decreases in vehicular delay.

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Transportation Control Measures / CMAQ Analysis

Under the transportation conformity regulation, Transportation Control Measures (TCMs) are strategies that

  1. are specifically identified and committed to in State Implementation Plans (SIPs); and
  2. are either listed in Section 108 of the Clean Air Act (CAA) or will reduce transportation-related emissions by reducing vehicle use or improving traffic flow such as improved public transit, traffic flow improvements and high-occupancy vehicle lanes, shared ride services, pedestrian/bicycle facilities, and flexible work.

Timely implementation of TCMs criterion must be satisfied before conformity determinations can be made. Consequently, TCMs receive the highest priority for funding under the Congestion Mitigation and Air Quality Improvement (CMAQ) Program. Off-Model methods have been developed to allow for emissions reduction analysis of these projects.

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Updated: 02/24/2014
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