PUSHING BEYOND REASONABLE LIMITS? INTERFACING TRANSPORTATION AND AIR QUALITY MODELS

After a decade of relative quiet, the analytical methodologies employed to support transportation air quality planning are being closely examined as a result of both the 1990 Clean Air Act and the 1991 Intermodal Surface Transportation Efficiency Act (ISTEA). With the initial base year mobile source emission inventories now complete and the real work of analyzing alternative control strategies still ahead, both transportation and air quality professionals are increasingly uneasy about the state-of-the-art of transportation air quality modeling. Considerable high-quality effort has been invested in the four-stage network analysis process, the Highway Performance Monitoring System (HPMS), and the MOBILE5 emissions model, yet important limitations still exist in interfacing these important analytical capabilities. Each was well designed for a specific purpose; each is now being extended beyond its original design intentions. Transportation variables affecting emissions are not necessarily the same ones that currently receive most emphasis in travel demand model systems. Rather than looking primarily at vehicle miles of travel as often was done in the past, emphasis is now being given to variables such as the number of trips, trip length, vehicle speed, engine operating mode, and even the length of time between vehicle trips. Current studies also are calling into question the validity of mobile source emission models and even the representativeness of the underlying Federal Test Procedure. Analysts indicate that actual emissions may be underestimated by a factor of two to three, if not higher. This paper first presents general observations concerning the analytical implications of the new Clean Air Act, and then describes examples of emerging analytical practices. Three basic questions are addressed: How good are current analytical capabilities? Can independently developed transportation and air quality models be successfully linked? What are the priorities for developing improved analytical capabilities? The overall conclusion is that while numerous incremental refinements are possible, a more fundamental rehabilitation of both transportation and emissions models is needed for the kinds of policies identified to be realistically evaluated.

• Supplemental Notes:
  • This paper appears in Volume II of the 4th National Conference on Transportation Planning Methods Applications, Session 6a: Air Quality Applications.
• Corporate Authors:

  Faris (Jerry M)

  1704 Thomasville Road, Suite 186
  Tallahassee, FL  United States  32303
• Authors:
  • Suhrbier, J H
  • Reinke, D
  • Ruiter, E
  • Rossi, T
• Conference:
  • 4th National Conference on Transportation Planning Methods Applications, Volumes I and II. A Compendium of Papers
  • Location: Daytona Beach, Florida
  • Date: 1993-5-3 to 1993-5-7
• Publication Date: 1993-9

Language

• English

Media Info

• Features: Figures; Tables;
• Pagination: p. 947-963

Subject/Index Terms

• TRT Terms: Air quality; Air quality management; Analysis; Conferences; Mathematical models; Mobile sources; Pollutants; Transportation; Validity
• Identifier Terms: Clean Air Act; Intermodal Surface Transportation Efficiency Act of 1991
• Uncontrolled Terms: Transportation models
• Old TRIS Terms: Analytical techniques; Clean air act 1990
• Subject Areas: Planning and Forecasting; Transportation (General); I72: Traffic and Transport Planning;

Filing Info

• Accession Number: 00639966
• Record Type: Publication
• Files: TRIS
• Created Date: Dec 8 1993 12:00AM