Appendix B: Glossary

The following words and terms, when used in this manual, have the following meanings, unless the context clearly indicates otherwise.

Commission — The Texas Transportation Commission.

control measure — Any measure specifically identified and committed to in the applicable state implementation plan.

district — A geographical area managed by a district engineer, in which the Texas Department of Transportation (TxDOT) conducts its primary work activities.

emissions reduction measure — A measure designed to reduce emissions from on-road vehicles.

farm-to-market (FM) or ranch-to-market (RM) road — A road shown in the records of the Commission to be a farm-to-market or ranch-to-market road.

may — Auxiliary verb used to indicate a permissive condition.

National Ambient Air Quality Standards (NAAQS) — Federal air quality standards established by the Environmental Protection Agency (EPA) to protect public health and welfare. NAAQS have been established for ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, particulate matter, and lead.

nonattainment county or nonattainment area — A county or counties in an air quality control region (area) for which a designated pollutant exceeds the National Ambient Air Quality Standards (NAAQS) for the pollutant as designated pursuant to 42 USC §7407.

shall — Auxiliary verb used to indicate a mandatory condition.

should — Auxiliary verb used to indicate an advisable but not mandatory condition; however, any reason for not following the instruction must be supported by sound engineering judgment.

State Implementation Plan (SIP) — The plan prepared by the Texas Natural Resources Conservation Commission as required by 42 USC §7410 to attain and maintain air quality standards. An approved SIP is the implementation plan, or most recent revision of this plan, which has been approved or promulgated by the Environmental Protection Agency.

Texas Manual on Uniform Traffic Control Devices (TMUTCD) — The manual, and any revisions, adopted by the commission as required under Transportation Code, §544.001.

Texas Commission on Environmental Quality (TCEQ) — The state air pollution control agency, which is the principal authority in the state of Texas on matters relating to the quality of the state’s air resources.

Traffic Engineering Section (TE) — A section in the Traffic Operations Division whose primary responsibility relates to traffic engineering.

Traffic Operations Division (TRF) — The division within the Texas Department of Transportation, headquartered in Austin, whose primary responsibility relates to traffic operations.

transportation conformity — A requirement for §176(c) of the Federal Clean Air Act. EPA’s transportation conformity rule (40 CFR Parts 51 and 93) and the Texas transportation conformity rule (30 TAC §114.260) contain the detailed requirements. Transportation conformity requires nonattainment and maintenance areas to demonstrate that estimated on-road mobile source emissions from metropolitan transportation plans (MTPs), transportation improvement programs (TIPs), and transportation projects conform to the purpose of the SIP, meaning that they will not cause or contribute to violations of air quality standards or delay timely attainment.

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