The Texas Department of Transportation (TxDOT) formed the TWG in the early 1990s in response to the CAAA of 1990, more specifically, according to the provisions of the Texas Administrative Code, Subchapter G: Transportation Planning, Sections 114.260 and 114.270, and of 40 CFR Part 93, Subpart A.

Paraphrased from the Texas Administrative Code, Section 114.260:

(C) For the purposes of evaluating and choosing a model (or models) and associated methods and assumptions to be used in hot spot and regional emissions analyses, agencies specified in paragraph (1)(A) of this subsection shall participate in a working group. The frequency of meetings and agendas for them will be cooperatively determined by the agencies specified in paragraph (1)(A) of this subsection.

The Texas Commission on Environmental Quality (commission) adopts an amendment to §114.260 and corresponding revisions to the Transportation Conformity State Implementation Plan (SIP). Section 114.260 is adopted with changes to the proposed text as published in the February 9, 2007, issue of the Texas Register (32 TexReg 499).

The adoption revises §114.260(d)(3)(C) by deleting the words identified as the Technical Working Group for Mobile Emissions and deleting the last sentence, The function of this working group may be delegated to an existing group with similar composition and purpose. The adoption revises §114.260(d)(5) by deleting the word involvement and replacing it with participation and renumbering the CFR reference for the fee schedule for public inspection and copying. These adopted revisions align the state rule with the federal rule; allow the executive director to delegate authority to staff without explicitly naming the designee; provide flexibility to the Technical Work Group; and bring existing rule language into agreement with Texas Register requirements, agency format guidelines, and guidance provided in the Texas Legislative Council Drafting Manual, August 2006.

It was originally designed for a small group of technical staff to work out problems or strategies for modeling on-road mobile source emission inventories. Since the early 1990’s the topics have grown to include policy discussions. The membership has grown considerably with the advent of the 8-hour standard and the potential new nonattainment areas. TxDOT – TPP has overall management responsibility for the TWG. The Texas Transportation Institute facilitates the meetings and provides other staff support for the TWG as part of a contract with TxDOT.