SIP Control Strategies

The State Implementation Plan (SIP) includes various emission control strategies implemented at the federal, state and local level to help reduce the ozone precursor emissions: nitrogen oxides and volatile organic compounds from all source categories. These measures are required by the Clean Air Act in areas designated nonattainment, based on a region's classification. Classification levels are assigned by the EPA based on several categories, including how high the region's design value (three-year average of the annual fourth-highest daily maximum 8-hour average ozone concentration) is above the current 8-hour ozone National Ambient Air Quality Standard.  Control Strategies, including Transportation Control Measures (TCM), were first introduced in the 1-Hour Ozone Standard Dallas-Fort Worth Attainment Demonstration (DFW AD SIP), adopted April 19, 2000.  The EPA approved each control strategy over a four-year period. 

Control Strategy Listing in the Current AD SIP

Transportation Control Measures

Transportation Control Measures (TCM) are transportation projects, programs, and activities designed to achieve on-road emission reductions by decreasing vehicle use or improving traffic flow and congestion conditions. Sections 182(c)(5) and 182(d)(1)(A) of the Federal Clean Air Act (FCCA) require states, under certain circumstances, include TCMs in the regions’ SIP. In addition, the transportation conformity rule, under 40 CFR 93.113 and 30 TAC 114.260, requires timely implementation of TCMs.

The North Central Texas Council of Governments (NCTCOG) tracks each TCM, ensuing projects and programs meet their target emission reductions in the specified time frame. Below is a listing of current TCMs along with State and Federal guidance.

Transportation Conformity TCM Listing
EPA TCM Guidance
TCEQ TCM Guidance

When a TCM is delayed for any reason, or is determined to no longer be appropriate, it may be substituted with another project creating equal or greater emission benefits. This TCM substitution process (30 TAC §114.270) was approved by the Environmental Protection Agency (EPA) on December 12, 2002 to allow the region to change the TCMs without a SIP revision. The substitution process includes interagency consultation and a public comment period to identify and evaluate possible substitution measures for TCM project(s) not implemented by the deadline. On September 27, 2005, the EPA approved the TCM substitution adopted by the Texas Commission on Environmental Quality on January 14, 2004, as part of the DFW AD SIP.

EPA TCM Substitution Guidance
Environmental Speed Limit Substitution
HOV Lane Substitution

Local Initiatives

NCTCOG has an assortment of locally implemented strategies in the DFW area including projects, programs, partnerships, and policies to reduce mobile source emissions. These local strategies are implemented in the 10-county nonattainment area with the intent to further reduce precursors to ground-level ozone formation. These initiatives are summarized in Appendix H of the DFW AD SIP.