With the development of vehicle emission estimation tools like the EST and the BEEM, the EPMPO has greatly enhanced its capabilities to understand the impact of motorized traffic in the El Paso area and, in particular, at the international border crossings. As part of the recommendations from recent Rider 7 projects as well as from stakeholder recommendations when presenting such work, its has been identified the need to better understand the Mexican side of the border region including urban growth patterns and the resulting traffic, not just within Juarez but its influence in the congestion at border crossings and in the El Paso area, as sources of ozone precursor emissions in the transborder region. Furthermore, special attention needs to be placed in the estimation of emissions rates from the Mexican motorized vehicle fleet, for use with the EST and the BEEM.