In the 2000 to 2004 PM research plan (Carr et al., 2002a) , five research focus areas were identified by the research community and transportation professionals. Five similar research focus areas were used to organize the literature assessment completed to develop this Strategic Plan (Tamura et al., 2005) . In the literature assessment, research issues were identified by focus area in tables at the beginning of each section; these tables have been updated in Appendix B of this document to reflect the priority of each need as discussed at the workshop.
This discussion section lists each of the five research focus areas and identifies the high-, medium-, and low-priority research needs in each focus area. Since Sections 3, 4, and 5 of this document are organized by research priority (high-, medium, or low-priority, respectively), this Section is intended to help readers find descriptions of research needs by focus area. More complete descriptions of important research needs are included in the Sections that follow.
Research Needs:
Characterization. The use of air quality or source receptor models and methodologies to relate ambient concentrations to local emissions sources, upwind sources, and meteorology. These tools are typically used by air quality planning agencies. This topic area does not include the emission or hot-spot models typically used by transportation planning agencies.
Research Needs:
Emissions Measurements. Direct quantification of vehicle emissions using tools such as dynamometers, remote sensing devices, and evaporative emissions sheds. This research focus area was identified as "Transportation Sources" in the 2000 to 2004 PM research plan.
Research Needs:
Research Needs:
Control Strategies. Measures used to reduce emissions with the intended consequence of improving air quality.
Research Needs:
For comparison, the research focus areas, key questions, and proposed projects from the 2000 to 2004 PM research plan are shown in Appendix C.
