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Find answers to common TREDIS questions here. For more information, check out the larger set of questions and discussion issues covered in the TREDIS Knowledge Base (Forum).


 TREDIS Fundamentals

Is TREDIS a benefit-cost tool or an economic impact tool?

TREDIS provides both types of analysis within the broader context of a “decision support system.” It provides a way to conduct and apply economic analysis (of benefit, costs and impacts) to inform public discussion of transportation-related policies and plans. And it provides a basis for project prioritization, ranking and funding decisions.

What is the difference between Benefit-Cost Analysis (BCA) and Economic Impact Analysis (EIA)?span>

In the transportation context, BCA is usually implemented as a comparison of project costs and user benefits, and is the first stage in a broader process of economic assessment.  It is sometimes referred to as engineering-based analysis because all of its elements – construction cost, traffic flow, safety and emissions – can be directly observed or estimated by transportation engineers and planners.  The results – a benefit/cost ratio and net benefit value – are calculated based on the assignment of monetary valuation factors for transportation-related improvements, which are based on either actual cost or a survey-based “willingness to pay.”  BCA is often used as an element in grant applications and project funding decisions.  

EIA, in contrast, assesses the wider effects on the economy – as reflected by jobs and income for area residents.  It goes well beyond direct user benefits to also consider how transportation projects can affect job access, product delivery markets, supply chain reliability, household budgets and business operating costs – leading to changes in productivity, business location patterns and ultimately employment and income growth for the affected area.  EIA is broader than user benefit analysis in BCA in that it considers wider economic effects on area residents (and not just traveler benefits), but it is narrower in that it does not consider personal time savings or other benefits that do not directly affect the flow of money in the economy (even though they may have a value to people).  There is great public interest in EIA for policy, planning and prioritization, and it is often used alongside BCA for project decision-making.  The TREDIS Economics Suite provides both BCA and EIA.  

For more information on BCA vs. EIA, see the USDOT video

What makes TREDIS different from other models or tools?

TREDIS covers all modes – including air, marine and non-motorized modes, as well as road and rail transportation. It follows through by showing how interactions and connectivity among modes makes a difference, and it uses that information to enable comprehensive coverage of wider economic benefits. TREDIS also provides views of economic impacts and benefits from alternative spatial, governmental and private sector perspectives. This is important because most public decisions are made by governmental agencies that represent specific spatial areas and constituencies.

What modes of transportation can TREDIS address?

TREDIS provides input forms for car, truck, bus, bicycle, pedestrian, passenger train, freight train, aircraft and boat. And it can distinguish among modal subgroups – e.g., delivery vans vs. large tractor trailer trucks, rail transit vs. commuter rail, regular vs. high speed trains, general aviation vs. commercial aircraft, container ships vs. passenger ferries, etc. This is important because these modal subgroups have very different speed and cost characteristics as well as dependent users and beneficiaries – all affecting the nature and size of economic impacts and benefits.

What is the smallest scale of study on which TREDIS can do a relatively accurate analysis?

Depending upon your needs, TREDIS can accommodate multi-state, state, corridor, county, and sub-county (zip code) economic impact and benefit cost analyses.

Who has used TREDIS?

TREDIS has been used in 43 US states and Canadian provinces. Subscribers include a wide set of state DOTs and MPOs, as well as local transportation agencies, universities and leading consulting firms. For a list of specific organizations using TREDIS, go to the web site section on TREDIS Users.

Can TREDIS be used for international (outside of USA) analyses?

TREDIS is currently being used in the USA, Canada, and Australia. TREDIS can be configured for metric or other measurement and currency units symbols.  Depending upon the economic and transportation data available, TREDIS can be configured to work in other nations.

Does the US DOT support the use of TREDIS?

The US government does not endorse any specific software or tools. However, staff of USDOT have reviewed the TREDIS fixed factor assumptions, and they have awarded rail grants and TIGER grants to some organizations that used TREDIS to generate benefit-cost and economic impact numbers for their applications. TREDIS was also designed to be compatible with FHWA’s highway benefit-cost guidelines and FAA’s s aviation user benefit-cost guidelines.

How can TREDIS help my organization get agency or public buy-in for a project or program?

TREDIS provides input forms tailored for relevance to different types of project and policy situations, and it provides separate reports tailored for communicating different types of benefits and impacts to legislators, elected officials, agency planners, business representatives and local residents.

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What information/minimum inputs do I need to get started in TREDIS?

The input requirements vary depending on the type of project or program being analyzed. In general, you need to provide three types of information: (1) the applicable mode of travel or type of facility, (2) the number of people, vehicles or trips affected, and (3) how they will be affected (which most often is a change in speed, travel time, cost, safety, capacity, reliability or access).

Do I need to have a separate Travel Demand Model in order to run TREDIS?

TREDIS does not require any travel demand model to generate its inputs. However, TREDIS does give users the option to make use of a travel demand model if desired.

Are there any special system requirements to install and run TREDIS?

There are no computer system requirements for use of TREDIS. The system is provided via an internet web site portal, using cloud-based servers. That allows you to access from nearly anywhere in the world, using nearly any computer hardware and software system that allows for internet access. You can even access TREDIS from a tablet computer or smart mobile phone.


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What data sources are used to run TREDIS?

TREDIS builds upon economic data from the US Bureau of Economic Analysis and US Bureau of Labor Statistics, demographic data from the US Census Bureau, interregional network impedances from Oak Ridge National Laboratories, domestic trade flows from Implan, international trade flows from WiserTrade, traffic and commodity flows from the Federal Highway Administration, baseline forecasts from Moody's Analytics, environmental factors from the US Environmental Protection Agency and the US Department of Energy, and spatial market data from ESRI. Optionally, TREDIS offers freight data sources including Transearch(R) and vFreighttm.  All of this data is built into TREDIS; there is no need for the user to obtain any further data other than inputs to describe the policy, project or program to be analyzed.

Is TREDIS a static or dynamic model?

The US version of TREDIS uses a dynamic, multi-regional economic impact simulation model to estimate impacts on employment and income growth over time. It incorporates economic geography and econometric response factors for cost and access changes, as well as labor market and income factors. The Canadian and Australian versions currently utilize state and provincial-level input-output models that have been combined with cost-response factors and baseline driver forecasts to simulate a long-range forecasting system.

Does TREDIS incorporate economic geography?

Yes. TREDIS is the only economic analysis tool that provides separate measures of market access and agglomeration benefits for labor markets and freight delivery markets, as well as productivity impacts of enhancing intermodal connectivity. And TREDIS is unique in backing this up with published journal articles, as well as presentations at European and American transport conferences.

Does TREDIS use a GIS system?

Yes. TREDIS data has spatial location tags, and derives market access measures by querying a GIS system to calculate population size within labor market areas and business activity within “same day” truck delivery areas.

Is TREDIS capable of sensitivity analysis? Can users assign low/high values to inputs?

The quick response features of web-based software make it easy for users to test alternative assumptions and quickly obtain information on how that affects results.

Are TREDIS upgrades or enhancements available to current users?

Yes. TREDIS data is updated and new features are added at least once a year, and active subscribers obtain access to the new versions whenever they are released. However, active users also have the option of staying on older versions with older data for studies that were started earlier. That way, the model will never change its forecasts or calculations of results for existing or earlier studies.

Can I do what TREDIS does in a spreadsheet?

The dimensionality of economic modeling calculations -- with trade and interactions between a large number of industries, commodities, regions, modes and time periods -- substantially exceeds the capacity of spreadsheets.

TREDIS is the product of an 10-year development effort encompassing over 250,000 lines of computer code, extensive databases consisting of over 1 TB of data from many unique sources, all constantly updated. TREDIS is hosted on high-speed, multi-processor cloud based servers.

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