Systems for Transportation and Economic Development Analysis, 2006
In recent years, new tools have been developed for MPOs, state DOTs and consultants to calculate the likely economic development implications of transportation projects and programs. Two systems that have received particular attention are TREDIS® and REMI TranSight. This month, we examine how their features compare. While they appear similar, TREDIS and TranSight actually address different sets of issues and also differ in their objectives for policy and program planning.
Design and Transparency. TranSight directly links results of a road network and travel demand model to the REMI Policy Insight macroeconomic model. The user may change inputs to the transportation model (changing car/transit mode split, vehicle volumes, speeds or distances) to represent alternative future scenarios. The system then automatically runs the macroeconomic model and generate estimates of long term economic impacts.
TREDIS, on the other hand, works in a very different way. It is designed to assist in project selection and assessment using alternative perspectives for viewing intermodal interactions and their benefits and costs. On the transportation end, it uses a broader set of information about multiple modes of passenger movement and freight movement and their interactions. This includes measures of highway, rail, sea and air movements for both freight and passenger travel, and associated measures of modal accessiblity and intermodal connectivity. On the economic end, it has modular features which allow it to work with a broad set of local and regional economic models, including REMI Policy Insight, REDYN, CRIO-IMPLAN, Global Insight and Canadian input-output models. As a modular system, it also generates and displays a series of intermediate calculations of traveler and non-traveler benefits and costs.
Portability. TranSight is software installed on a single computer, with predefined regions specified at the time of ordering the system. TREDIS is web-based system which allows for simultaneous use and collaboration among agencies, universities and consultants located in different areas. The regions can be redefined and reconfigured by the user. TREDIS gives users a larger set of inputs to fill in, covering market access changes as well as vehicle flow changes, but users have the option to use or ignore these elements as desired.
Coverage. TranSight allows users to portray impacts in terms of multiple time periods and modes of travel, including car, truck, bur, passenger rail and light rail. It also portrays freight movement by truck. The air, sea and freight rail modes are not integrated into this transport modeling process, though they can be analyzed via separately developed analysis efforts. While TranSight works at the county, multi-county or statewide level, TREDIS offers a higher geographic resolution which can go down to the city or town level. It also goes beyond urban ground transport to cover not only passenger car, light truck, freight truck, bus, and light rail transit, but also addes rail freight, intercity passenger rail, passenger aviation, freight air, marine passenger and freight categories.
Spatial Aspect of Transportation Projects. TranSight utilizes economic geography by estimating how transportation projects can change the “effective distance” between regions on the basis of a composite average ground travel time or cost between county centers. TREDIS takes a more finely-defined approach, using a Geographic Information Systems (GIS) to evaluate how alternative projects may affect intermodal connectivitiy and travel times to airports, marine ports, intermodal rail terminals, highway networks and delivery access for different modes and trip purposes.
Pricing. TranSight is available as a software rental or purchase, with an annual fee for updates. TREDIS is available as a subscription service.
Making a Selection. TranSight and TREDIS are not necessarily competing head-on. After all, TranSIght focuses on measuring economic growth impacts of ground transport changes, while TREDIS focuses on measuring benefits, costs and other impacts of multi-modal projects which may include ground-air-sea interactions.
The appropriate choice may also depend on user preferences and needs, when considering tradeoffs between an integrated software package that runs automatically but with limitations on its intermodal applications, or a modular web-based system with broader multi-modal applications that involves more user decisionmaking. The price comparison can differ, depending on the number of regions and length of time for the rental or subscription.