Emissions Analysis Techniques for TCMs
Overview - The Intelligent Transportation System (ITS) Deployment Analysis System (IDAS) is a modeling tool that enables the user to conduct systematic assessments and quantitative evaluations of the relative benefits and costs of more than 60 types of ITS investments, in combination or in isolation. IDAS has been tested in three metropolitan areas and is currently being applied in seven additional areas.
Strategies Addressed - Improved transit; HOV lanes; traveler information; traffic flow improvements; incident management.
Methodology - The model utilizes network and trip data from the regional transportation model. Strategies are applied either for links in the transportation network or at the traffic analysis zone level. Strategies that affect the time or cost of travel affect mode choice, temporal choice, and induced/foregone demand through a "pivot-point" model, which is based on coefficients from the regional travel model. Other strategy impacts are based on findings from various empirical studies. Changes in trips by mode, time of day, and origin/destination subsequently affect vehicle speeds and volumes. Emissions are calculated based either on default or user-input MOBILE5 or EMFAC emission factors by speed range.
Data Requirements - Transportation network and trip tables by mode and/or purpose, which can be obtained from the regional travel model; deployment of ITS strategies by type and location on the transportation network.
Outputs - Changes in vehicle-trips, VMT, emissions; travel time savings and improvements in travel time reliability; energy consumption, noise impacts, safety impacts, and monetary values of these changes; and lists of ITS equipment and costs.
Level of Effort - Familiarity with travel demand model structure and output is required in doing initial set-up for the model. Some effort is also needed to identify the various ITS improvements to be analyzed. Data entry and alternatives analysis are conducted in a user-friendly Windows environment.
Advantages - IDAS can analyze the benefits of a wide range of ITS strategies. It can also analyze "generic" strategies affecting travel time or cost that are input for transportation links or analysis zones. Changes in emissions are based on network-wide VMT and speed impacts, consistent with network data used in regional travel modeling. The model can account for time-of-day shifts, induced demand, and changes in travel time reliability.
Limitations - IDAS requires some time investment to learn and some user skills; in particular, it is helpful to have familiarity with travel model data in setting up the model. Run time is non-trivial (anywhere from a few minutes to a few hours, depending on the number of zones and other factors.)
Source/Availability - IDAS was developed for FHWA and is distributed through: