Glossary
| Term | Definition |
|---|---|
| Alternative | Within a TREDIS project, alternatives such as Base (no-build) and Project (build) are compared |
| Analysis Type | TREDIS adapts the user inputs and available results to match where in the transportation planning cycle the user project falls. In addition to the Advanced Mode, TREDIS includes Public Policy, Vision Planning, Prioritization, Alternatives Analysis, Single Project, Existing Facility, and Asset Management Types. |
| Access | See Market Access |
| BCA | Benefit Cost Analysis. Click here for detailed explanation |
| Buffer Time | Refers to the hours that travelers must set aside for each vehicle trip in addition to their travel time in order to arrive on-time 95% of trips. Average buffer time per trip is related to average travel time per trip by the buffer time index. TREDIS can estimate needed buffer time per trip based on the information you provide on total Trips, total VHT, and percent of VMT congested (V/C > .9). |
| Constant Dollar Year | The adjusted value of currency used to compare dollar values from one period to another. |
| Construction Period | The schedule years when a project's construction activities occur. This period ranges from the Construction Start Year to the Construction End Year |
| Contingent Development | Refers to discrete jobs or business sales attracted to the region due to the transportation improvement – the development of this economic activity is contingent on completion of the project. Contingent development within the market access inputs section of TREDIS can be used when the agency has more specific information on land development or job attraction that should be included as well as estimates from transportation cost savings and expansions of the labor market or same day deliver market areas. |
| Contract | TREDIS organizes subscriptions using the concept of contracts. The contract contains information about the geographies the user may access and time period the subscription is active. |
| Costs | Costs are the project expenditures made during the Construction Period and then the operating and maintenance expenditures during the Operations Period. |
| Cost Elements: | Property Acquisition: Right-of-way purchases or easements Engineering and Design: Soft costs of construction, including planning, analysis, legal, architectural, engineering, and design work. Right of Way: Earthmoving, grading, drainage, and paving. For railroads, this includes all expenditures on the laying of rails; for airports, this includes runway construction. Transport Structures: Construction of culverts, road bridges, flyovers, railroad bridges, and marine docks Terminal: Operations offices, maintenance facilities, airport/bus/rail terminals, or storage buildings Vehicles: Acquisition of rail cars and engines, ferries, airplanes, barges, or maintenance or service vehicles Ongoing Operations: Cost related to transit service operation, highway toll collection, systems operation, or incident management Maintenance and Rehabilitation: Crack repair, repaving, or vegetation control; also includes vehicle servicing. |
| CO2 | Carbon Dioxide (pollutants) |
| Custom Mode | A custom mode is a user created mode, based on an existing mode which can have different default values. Custom modes are shared among all members of the user's account, with the user who created the custom mode uniquely able to edit the default values. |
| Direct Impact | The effect of cost savings to system users under the transportation scenario modeled, or spending by the operator or constructing entity of a project or service. |
| Discount Rate | Cost of capital (interest rates). Note: TREDIS uses the default values of 3% and 7%, which corresponds to the values typically used in grant applications, although the user may change these values prior to running the analysis on the Results - Settings screen. |
| EIA | Economic Impact Analysis. Click here for detailed explanation |
| Environmental Factors | This deals with emissions generated by the vehicles in the project. Factors include tons of emissions (VOC, SO2, NOX, PM, and CO2) per vehicle mile traveled both free flow and congested, along with the cost per ton of these pollutants. |
| FIA | Financial Impact Analysis. Click here for detailed explanation |
| Fraction Congested | Fraction of time all vehicles for a specific mode-purpose are experiencing congestion (values range from 0 - 1.0) |
| Fraction of Trips: Incoming | Fraction of trips (0 - 1.0) that originate outside the study region and end in the study region |
| Fraction of Trips: Internal | Fraction of trips (0 - 1.0) that originate in the study region and also end in the study region |
| Fraction of Trips: Outgoing | Fraction of trips (0 - 1.0) that originate inside the study region and end outside the study region |
| Fraction of Trips: Through | Fraction of trips (0 - 1.0) that originate outside the study region and end outside the study region |
| Indirect Impacts | The effect of spending by the suppliers to business users benefiting from system improvements, or suppliers of operators or constructing entities of a project or service. |
| Induced Impacts | The effect of household spending due to additional employment and payroll generated by direct and indirect impacts. |
| Labor Income | Labor Income includes employee compensation and proprietor income. In TREDIS, it represents the additional wages, salaries, and benefits for employees and new income for proprietors from the scenario analyzed. |
| Labor Market | The labor market affected by a project is considered to be the number of residents within a 40 minute trip of an employment center affected by the project. TREDIS default labor market values are based on the population within a 40 minute drive-time from the population-weighted centroid of a county. On the Summary graphic, TREDIS shows the percent improvement which you indicated your project is expected to provide. |
| Linked Area | Regions directly connected to study region, defaults to geographies within study region, but may be overwritten. (Contact your account manager to add linked areas that are outside your subscribed account regions) |
| Local Market | Approximate 40-minute commute time (way). The threshold at which most employees are willing to travel. |
| Market Access | Translates changes in market access and intermodal connectivity into effects on agglomeration, dispersion and scale economies for industry sectors. It applies calculation methods backed by peer-reviewed publications for estimating wider economic impacts. |
| Mode | Transportation type, such as passenger car, truck, and bus used in the Project analysis |
| NOX | Nitric Oxide and Nitrogen Dioxide (pollutants) |
| Occupational Aggregation | Refers to the number of digits of Standard Occupational Classification (SOC) codes to use when reporting economic impacts by occupation. The SOC system is developed and published by the U.S. Bureau of Labor Statistics and used for their reporting. TREDIS offers 2-, 3-, and 4-digit SOC Code aggregation. |
| O & M | Operations and Maintenance - see Cost Elements for Ongoing Operations, and Maintenance and Rehabilitation. |
| Operations Period | The period of time when the transportation system is in operation and is incurring operating and maintenance costs. This period ranges from the Operations Start Year to the Operations End Year. |
| Output | Output represents the value of industry production. For manufacturers, this would be sales plus/minus change in inventory. For service sectors production, output is simply the value of sales. For Retail and wholesale trade, output is represented by gross margin and not gross sales. Margin is sales receipts less the cost of goods sold. |
| Period | A time period specified at the Project Level, defined solely by its travel demand characteristics. Multiple periods may be used to model differences in peak vs. off-peak or seasonal differences resulting from road closures. |
| Period Veh-Trips | The number of one way trips made by all vehicles during the period (annually for example) |
| PM | Particulate matter (pollutants) - complex mixture of extremely small particles and liquid droplets in air. Particle pollution is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles. |
| Productivity | The average measure of the efficiency of production, which is expressed as the ratio of the outputs to the inputs as used in the production process, i.e. output per unit of input. |
| Project | The major unit of a TREDIS analysis defined by certain parameters being held constant. It has the following features: (1) the geography (Region) is constant over the entire analysis, (2) all Alternatives within the Project have the same time horizon (that is, the same Construction Period and Operations Period), and (3) certain parameters such as the discount rate, are "fixed" across Alternatives when they are being compared. |
| Project Group | TREDIS allows the user to organize collections of projects in groups. The criteria for organizing is up to the user and may be elements such as user projects, team projects, archived projects (for saving older projects), etc. |
| Purpose | Trip purposes are used to classify why a trip is taken and is associated with a mode to form a mode-purpose combination. The trip purposes will fall into one of the following five categories: Business, Personal, Commute, Freight, or No Split (which is the combination of the previous four selections.) |
| Results Year | Year used for presenting TREDIS results, typically in the future |
| Same-Day Market | Approximate 180-minute (3-hour) drive time for a same day truck delivery of goods. Allows for delivery and truck return to warehouse the same day. |
| STCC | The Standard Transportation Commodity Code (STCC) is a publication containing specific product information used on waybills and other shipping documents. A STCC code is a seven digit numeric code representing 38 commodity groupings. |
| SO2 | Sulfur Oxides (pollutants) |
| Study Region | Geographic areas where the Build Alternative takes place. These study areas may be as small as a zip-code or as large as a collection of states. A project may have 1 or more Regions (up to 10). |
| Supply Chain | Refers to the same day delivery market for an employment center modeled by the project. It conversely considers the establishments that can serve your employment center with same day delivers. TREDIS estimates Supply Chains based on the employment at establishments within a 3 hour drive time. Default values for supply chain area employment are based on the employment-weighted centroid of a county. On the Summary graphic, TREDIS shows the percent improvement which you indicated your project is expected to provide. |
| Terminal | An intramodal transfer facility such as an airport, marine port, or rail facilities (passenger and freight) |
| Time/Value Factors | Default values used by TREDIS to address costs per crew member, passenger, and freight logistics, as well as buffer time costs and out of vehicle transfer costs |
| Travel Characteristics | Translates changes in traffic volumes, vehicle occupancy, speed, distance, reliability and safety into direct cost savings for household and business travel. It applies practices for travel modeling and economic valuation that are widely accepted by metropolitan, state and federal agencies. |
| TREDIS | Transportation Economic Development Impact System |
| Truck L-T-L | Truck L-T-L refers to Less than Truckload shipping. This Mode is used to describe trucks used where a shipment does not require a full 48- or 53-foot trailer. Examples are lift gate and residential pickups and deliveries, etc. |
| Truck PVT | Refers to "Private" truck freight. |
| Truck NEC | Refers to truck freight "Not Elsewhere Classified." |
| Useful Life | The useful life of a facility describes the number of years after which a facility is considered to be obsolete and in need of replacement. TREDIS uses information on the useful life of project investment categories to determine the residual value of those investments at the end of the analysis period. At the completion of construction, investments begin depreciating at a rate tied to the useful life factor. |
| Value Added | Value Added changes from a project can also be considered as changes in Gross Regional Product or GDP. Value Added is the difference between an industry’s or establishment’s total output and the cost of intermediate inputs. It consist of employee compensation, taxes on production and imports less subsidies, and gross operating surplus (similar to profit). |
| VHT | Vehicles Hours Travelled |
| VMT | Vehicle Miles Travelled |
| VOC | Volatile Organic Compounds (pollutants) |