Emissions Analysis Techniques for TCMs
Overview - The Off-Network Tool Set (Off-Net) and PAQONE are similar sketch-planning tools designed to estimate the emissions benefits of TCMs that cannot be readily analyzed using traditional transportation models.
Strategies Addressed - Improved transit; park and ride; employer-based TDM; bicycle and pedestrian facilities; traveler information; traffic flow improvements; incident management.
Methodology - A variety of methodologies are used, including sketch-planning analysis, elasticities, and highway/traffic engineering principles from the Highway Capacity Manual. Vehicle-trips are distributed by time of day and work versus non-work trips. VMT changes are distributed by time of day, facility type, and area type. A stand-alone emissions module runs MOBILE to develop emission factors. Project and scenario data are stored in a Microsoft Access database.
Data Requirements - A variety of different inputs are required, depending on the strategy analyzed. These include factors such as existing transit boardings on affected routes, population of transit or bicycle route service areas, baseline speeds and volumes on affected roadways, and changes in transit, bicycle, or roadway service characteristics. Travel outputs are designed for use in conjunction with VMT and speeds by facility type, as can be obtained from regional travel model output.
Outputs - Vehicle-trips, VMT, emissions.
Level of Effort - The models are Windows-based applications that are easy to use. The software includes a scenario management function. Some effort is required to develop baseline data and assumptions.
Advantages - The models are designed to analyze a variety of transit, non-motorized travel, and roadway improvements that cannot readily be analyzed through other means, or in a sketch-planning fashion with limited data requirements. The use of VMT and speed data by facility type is designed to make the model output consistent with emissions estimates for conformity analysis based on travel demand models.
Limitations - A number of the assumptions in the model that determine strategy effectiveness are based on judgment or rules of thumb. Appropriate assumptions may vary from place to place, and impacts may vary locally based on factors not included in the model.
Source/Availability - The underlying methodologies were originally developed for the Pennsylvania DOT by COMSIS Corporation in 1993. They have recently been adopted for Illinois DOT by Cambridge Systematics, Inc. with Michael Baker Associates and E.H. Pechan into a Windows-based software package known as Off-Net. PAQONE is a similar package developed by Michael Baker Associates for PennDOT to include additional employer-based and regionwide TDM strategies, to assist MPOs with CMAQ analysis. The original PennDOT procedures have been applied by other states for CMAQ and conformity analysis. The models could be adapted for use by other areas with minor modification.
Contacts - Illinois DOT - Tim Milam (217-524-9067) or Susan Stitt (217-782-2863). Cambridge Systematics, Inc. - Don Vary (202-466-5542) or Dan Beagan (617-354-0167). PennDOT - Mike Baker (Program Center) (717-772-0796). Michael Baker Associates - Robert Kaiser or Jim Frazier (410-571-8706).