Emissions that lead to the formation of ozone have distinctive temporal patterns, and the chemistry of ozone formation is non-linear and introduces time lags between emissions and ozone formation. As the transition is made between the 1-hour ozone National Ambient Air Quality Standard (NAAQS) and the 8-hour NAAQS, critical questions arise about the effectiveness of potential new mobile source control strategies for reducing 8-hour averaged ozone concentrations in Texas non-attainment areas. This project had two primary objectives. The first objective was to examine the relative effectiveness of potential new emission control measures, primarily from mobile sources, on 1-hour and 8-hour ozone concentrations and population exposure metrics in the Houston and Dallas areas. The second objective was to conduct a pilot-scale study to examine how portable emissions monitoring system (PEMS) technology can be used to characterize exhaust emissions from heavy-duty diesel vehicles and equipment during real-world driving conditions. The overall goal of the research was to provide a foundation for effective transportation and air quality policy decisions in eastern Texas. A total of 38 modeling simulations were conducted to examine a range of emission control strategies. This modeling indicated that even with reductions in on-road and non-road mobile source emissions greater than 40%, at least one monitor in each area is still predicted to remain in non-attainment. Given these challenges, it is recommended that the Texas Department of Transportation (TxDOT) continue to investigate eligibility for Texas Emission Reduction Program (TERP) funding to reduce NOx emissions from on-road heavy-duty diesel vehicles and non-road equipment (particularly diesel construction equipment) and continue to pursue effective emission control strategies that can be adopted both locally and statewide to assist in obtaining regional NOx reductions. The pilot-scale PEMS study demonstrated the successful deployment of the Sensors, Inc. SEMTECH-D PEMS on single-axle and tandem-axle dump trucks during typical TxDOT operations. Idling accounted for the most significant fraction (20%–46%) of the duty cycle and had the highest average and median fuel-specific emission factors for all pollutants. TxDOT should continue to examine the idling practices of its dump trucks with respect to the impacts on both emissions and fuel consumption. Differences in emissions between non-idling modes of operation varied by pollutant. CO2 and NOx emissions were reasonably consistent between non-idling modes; CO and THC emissions exhibited greater variability with differences of a factor of two, or three in some cases. The range of NOx emission factors measured in this study showed very good agreement with emission factors measured through chassis dynamometer testing of the same engine types by Baker et al., (2004), and were well within the range of values reported in other studies. TxDOT should continue to characterize baseline emissions from other on-road and non-road equipment besides dump trucks during typical operations, as well as examine the effectiveness of new fuels and fuel additives and new after-market emission reduction technologies that will be emerging from TERP, the New Technology Research and Development (NTRD) Program, and similar state or national-scale incentive programs.