Emissions Analysis Techniques for TCMs
Overview - TCM Tools is a sketch-planning model designed to calculate the cost-effectiveness of a wide range of TCM measures at achieving emissions reductions. It has been applied in a number of metropolitan areas such as San Diego, Houston, and Tucson.
Strategies Addressed - Improved transit; HOV lanes; park and ride; carpooling and vanpooling promotion; employer-based TDM; bicycle and pedestrian facilities; telecommuting/work hours; pricing/subsidies; land use.
Methodology - TCM Tools is intended for the analysis of strategies employed at a regionwide level. The Transportation Module, a spreadsheet application, calculates changes in peak and off-peak vehicle trips, VMT, and vehicle speeds on an area-wide basis. For some strategies, travel changes are estimated based on elasticities; for others, program participation must be estimated by the user. The Emissions Module, a Fortran program, estimates reductions in emissions based on changes in travel characteristics (VMT, trips, and speed) and MOBILE or EMFAC emission factors.
Data Requirements - User inputs to the Transportation Module include baseline travel characteristics (number of person-trips, percent of trips in peak period, etc.) and behavioral assumptions (elasticities or participation) for the strategy being analyzed. The Emissions Module requires data on VMT and speeds by six facility types, along with other data (such as vehicle registration distributions and ambient temperatures) that are typically developed for analyses using MOBILE.
Outputs - Changes in mode share, vehicle-trips, VMT, average travel speed, and emissions.
Level of Effort - The Transportation Module is relatively easy to apply. Running the Emissions Module in conjunction with the Transportation Module is a multi-step process, and requires some initial effort to develop inputs.
Advantages - The strength of the model is as a calculation aid, in which the user can input various assumptions regarding program characteristics, behavioral responses, and costs, and can compare the magnitude of impacts for different strategies and assumptions.
Limitations - The model is limited in its ability to forecast the travel impacts of TDM strategies; many strategies require the user to estimate participation rates (e.g., telecommuting participants, number of new walkers/bicyclists), as well as to make other assumptions that affect the magnitude of travel impacts. The ability of the software to manage scenarios is limited.
Source/Availability - TCM Tools was developed in the early 1990s by Sierra Research with assistance from JHK Associates, and has since been customized for applications in various areas. For more information, contact Cecilia Ho, FHWA Office of Natural Environment (202-366-9862); or Bob Dulla, Sierra Research (916-444-6666).