IDAS is an ITS sketch-planning analysis tool that can be used to estimate the impacts, benefits and costs resulting from the deployment of ITS components. IDAS operates as a post-processor to travel demand models, used by Metropolitan Planning Organizations (MPO), by local agencies, and by State Departments of Transportation (DOT) for transportation planning purposes. IDAS, although a sketch-planning tool, implements the modal split and traffic assignment steps associated with a traditional planning model. These steps are key to estimating the changes in modal, route, and temporal decisions of travelers resulting from ITS technologies. Because IDAS is a sketch planning analysis system, it is intended for use as an alternatives analysis tool and not for ITS operations optimization.

The set of impacts evaluated by IDAS include changes in user mobility, travel time/speed, travel time reliability (non-recurring congestion duration), fuel costs, operating costs, accident costs, emissions, and noise. The performance of selected ITS options can be viewed by market sector (mode), facility type, and district. IDAS produces outputs of the results in a benefit/cost summary report and performance summary reports. Given the diverse types of performance measures that may be impacted by ITS, and the requirements to provide a comprehensive analysis tool, IDAS is comprised of five different analysis modules:

• An Input/Output Interface Module (I/O);
• An Alternatives Generator Module (AGM);
• A Benefits Module;
• A Cost Module; and
• An Alternatives Comparison Module (ACM).

The Benefits Module is further comprised of four submodules: Travel Time/Throughput, Environment, Safety, and Travel Time Reliability. Within each of these submodules, both traditional benefits of ITS deployment (e.g., improvement in average travel time) and non-traditional benefits (e.g., reduction in travel time variability) are estimated. [See IDAS Model Structure - The circled numbers refer to specific chapters of the IDAS User's Manual available under the Documentation heading].

The IDAS Cost Module estimates the life-cycle expenditures by year and the average annual costs for ITS improvements. The cost estimates include public sector capital costs, public sector operating and maintenance costs, private sector capital costs, and private sector operating and maintenance costs. The Cost Module compiles costs based upon the inventory of ITS equipment associated with the ITS components deployed by the user. These costs were obtained from the National ITS Architecture and updated information, and are modifiable by the user.