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GLOSSARY Accessibility Accessibility measures the relative ease with which one can reach desired destinations. See mobility. Activity space Geographic space within which a population tends to circulate. Affected population Population that would experience the beneficial and adverse effects of a transportation system change. Air quality index (AQI) An index for reporting daily air quality. It focuses on health effects due to breathing polluted air and includes five major pollutants: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. American Association of State AASHTO is a nonprofit, nonpartisan association Highway Transportation Officials representing highway and transportation departments (AASHTO) in the 50 states, the District of Columbia, and Puerto Rico. American Society for Testing Founded in 1898, ASTM International is a not-for- Methods (ASTM) International profit organization that provides a global forum for development and publication of voluntary consensus standards for materials, products, systems, and services. ALOHA model Areal Location of Hazardous Atmospheres (ALOHA) model. Artist's sketches A method of presenting alternative proposals for a transportation facility whereby respondents can react to renderings of aesthetic features. Average annual daily traffic (AADT) The average number of vehicles passing a point on a roadway per day based on an annual average of daily traffic rates. Actual daily traffic rates may vary somewhat from the AADT because of seasonal variations, special events, and other phenomena. Barrier effect The reduction in mobility and safety of nonmotorized travel caused by the construction of new transportation projects such as those that increase traffic volumes and speeds on existing roads. 351

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Benefit-cost analysis An analysis that compares the potential benefits of a project with the estimated costs of the project. If the potential benefits outweigh the expected costs, the analysis suggests that the project will benefit society in general. Bicycle Compatibility Index (BCI) A composite level-of-service measure for bicycle condition evaluation. Standard BCI values represent abilities and preferences of average adult cyclists. Bicycle Safety Index (BSI) An index that enables one to estimate the safety of bicyclists riding on a roadway that has certain characteristics. These characteristics include traffic levels, speed limit, and a series of physical attributes. Categorical exclusion (CE) A component of the NEPA process. A CE can result from a determination that a project would have no significant environmental impacts and therefore that an expedited permitting process can be followed. See environmental assessment and environmental impact assessment. Census Transportation Planning A data package available from the U.S. Census Package (CTPP) Bureau for most major metropolitan areas that contains demographic data and self-reported journey- to-work travel times. The data are available by jurisdiction within the metro area. Charrette A meeting to resolve a problem or issue. Within a specified time limit, participants work together intensely to reach a resolution. The sponsoring agency usually sets the goals and time limit and announces them in advance. Chi-square test A statistical test that can be used to determine if a particular type of impact would be experienced differently by protected populations. Community cohesion The amount and quality of social networking among members of a community. Comprehensive Environmental The federal law otherwise known as "Superfund" Response, Compensation and under which hazardous waste remediation is Liability Act (CERCLA) conducted. Computer-aided design and drafting Computer graphics software that is commonly used to (CADD) software make architectural and engineering drawings and for making technical illustrations of any kind. It also 352

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enables you to revise drawings quickly and with minimal effort. Consolidated Federal Regulations A compilation of proposed, new, and amended federal (CFR) regulations that have been published in the Federal Register. Cost-effectiveness analysis Several alternatives are compared to determine which would achieve the desired outcome at the lowest cost. Council on Environmental Quality Coordinates federal environmental efforts and works (CEQ) closely with agencies in the development of environmental policies and initiatives. The CEQ has oversight of the federal compliance with Executive Order 12898 and NEPA. Descriptive statistics The branch of statistics concerned with (1) summarizing the distribution of a single variable or (2) measuring the relationship between two or more variables. Distributive effects Measurable adverse and beneficial outcomes of a transportation plan, program, or project that do not affect all people within an area equally. Distributive effects analysis An analysis that compares potential effects, positive and negative, of publicly funded projects or services on various population groups and (in some instances) on individuals or subgroups within groups. Double-counting Counting a particular effect twice, either explicitly or implicitly. For example, adding transportation cost savings to the economic effects brought about by these savings may result in an overestimation of the economic effect of a project. Economic development The process of expanding economic activity in an area to provide more jobs and income to that area's residents. Emergency Response and The primary national database used to report and track Notification System (ERNS) hazardous material spills. Emissions factor (EMFAC) The relationship between the amount of pollution produced and the amount of raw material processed. Environmental assessment (EA) A component of the process mandated by the National Environmental Policy Act of 1970, as amended. An 353

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EA is a concise public document that includes a brief discussion of the rationale behind the proposed project, alternatives to the proposed action, the probable environmental impacts of the proposed action and its alternatives, and a listing of agencies and persons consulted. The EA must show why the impacts are not significant or how they can be mitigated to become nonsignificant. Environmental impact statement Also a component of the NEPA process. An EIS is an (EIS) analytic document that informs decision-makers and the public of the potential environmental effects of the proposed project, as well as those of any reasonable alternatives. It must be completed when impacts would likely be significant, and it must show how they would be mitigated. Environmental justice Environmental justice is concerned with a variety of public policy efforts to ensure that adverse human health or environmental effects of governmental activities do not fall disproportionately upon minority populations and low-income populations. Environmental Justice Index (EJI) An index describing level of environmental justice concerns based on minority population, low-income population, and population density factors. Executive Order (EO) 12898 An executive order on environmental justice signed by President Clinton on February 11, 1994. The order obligates each federal agency to identify and address disparate effects of policies, programs, and activities on low-income populations and minority populations. Equity An often-elusive concept that pertains to fairness of distribution of the benefits and costs of a transportation project among population groups. There are several measures of equity but, in the end, what is equitable depends on personal, individual definitions of fairness. Federal Highway Administration The administrative unit within the U.S. Department of (FHWA) Transportation charged with improving and maintaining designated roadways across the nation. It also is responsible for carrying out various federal policies that apply to surface transportation. 354

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Federal Insecticide, Fungicide and The primary focus of FIFRA is to provide federal Rodenticide Act (FIFRA) control of pesticide sale, distribution, and use. Federal Transit Administration (FTA) The FTA assists in developing improved mass transportation system for cities and communities nationwide. Through its grant programs, FTA helps plan, build, and operate transit systems with convenience, cost, and accessibility in mind. Finite element flow (FEFLOW) A model that provides an advanced two-dimensional and three-dimensional environment for performing complex groundwater flow, contaminant transport, and heat transport modeling. Fixed-guideway transit Any public transit service that uses exclusive or controlled rights-of-way or rails. This includes heavy rail, commuter rail, light rail, trolleybus, aerial tramway, inclined-plane cable car, automated guideway transit, ferryboats, and the portion of motor bus service that operates on exclusive or controlled rights-of-way and high-occupancy or toll (HOT) lanes. Focus group A small group discussion with professional leadership. A carefully selected group of individuals convenes to discuss and give opinions on a single topic. Participants are selected in two ways: (1)random selection is used to ensure representation of all segments of society or (2) nonrandom selection can help clarify a particular position or point of view. Geographical information system A computer system capable of assembling, storing, (GIS) manipulating, and displaying geographically referenced information. GIS enables spatial data files to be layered for purposes of analysis or presentation. Global positioning system (GPS) A worldwide radio-navigation system involving a constellation of 24 satellites and their ground stations. GPS receivers use signals from these satellites to accurately compute positions relative to the face of the earth. GMS 4.0 (Groundwater Modeling A comprehensive program with tools for every phase System) of a groundwater simulation, including site characterization, model development, postprocessing, calibration, and visualization. Gravity model A method of analysis that generally assumes the number of trip ends at a destination location to be 355

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proportional to the size or attractiveness of the destination and inversely proportional to a measure of separation between this location and various origin zones. Gravity models are routinely used in travel demand models to forecast how many trips will be made to each destination from a given origin. Ground-level air quality (microscale, Air quality in the lower atmosphere very near the or hot spot) source of emissions, such as around an intersection. Corps of Engineers Hydraulic A water surface profile model for steady and unsteady Engineering Center River Analysis one-dimensional, gradually varied flow in both natural System (HEC-RAS) and constructed river channels. HEC-2 A water surface profile model for steady, gradually varied flow in natural and constructed channels. Highway Economic Requirements A computer model developed for FHWA to assist Model (HERS) and HERS-ST state and local governments in programming their highway resources. HERS contains routines to estimate the economic benefits of potential transportation projects. Highway Performance Monitoring A national highway information system that includes System (HPMS) data on the extent, condition, performance, use, and operating characteristics of highways. Horizontal equity Horizontal equity refers to the equitable distribution of benefits and costs within a group. Incident An event that reduces the performance level of a roadway, including crashes, vehicle breakdowns, and debris on the road. Incidents are random events, but the likelihood of their occurrence is affected by the design and condition of the roadway, as well as by the congestion level on the roadway. Initial Isolation Zone (IIZ) The radius of a zone around an accidental release of toxic chemicals from which all people not directly involved in emergency response are to be kept away. ISTEA Intermodal Surface Transportation Efficiency Act of 1991. Leaking underground storage tank Underground storage tanks (e.g., gasoline) that have (LUST) uncontained leaks. 356

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Level of service (LOS) A concept that describes traffic conditions and associated traffic flow rates. Six levels of service are typically recognized: A (free flow) through F (stop- and-go waves). The concept of LOS also is applied to gauge the performance of nonmotorized transportation (e.g., the ability of pedestrians to cross a major urban street). Likert scale A composite measure that attempts to improve levels of measurement through the use of standardized response categories in survey questionnaires. Response categories may include strongly agree, agree, neither agree nor disagree, disagree, and strongly disagree. Major investment studies (MIS) Federally mandated studies in which MPOs examine which alternative transportation strategy, or mix of strategies, would best solve transportation problems within particular corridors. Metropolitan Planning Organization A transportation policy-making organization made up (MPO) of representatives from local government and transportation authorities. They are required for any urbanized area with a population greater than 50,000. Federal funding frequently is channeled through MPOs. Mobile Emission Assessment System Model-based method used for developing pollution for Urban and Regional Evaluation surfaces. (MEASURE) Mobility The ability of people to move about and make use of various transportation modes. See accessibility. Mode The method of transportation by which people travel or goods are shipped. Motor Carrier Management The Federal Motor Carrier Safety Administration Information System (MCMIS) (FMCSA) operates and maintains the MCMIS. MCMIS contains information on the safety fitness of commercial motor carriers and hazardous material (HM) shippers subject to the Federal Motor Carrier Safety Regulations (FMCSRs) and the Hazardous Materials Regulations (HMRs). National Ambient Air Quality Directed by the 1990 Clean Air Act and created by the Standards (NAAQS) U.S. EPA, these standards are designed to protect human health and the public welfare. Primary 357

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standards protect human health; secondary standards protect public welfare. National Environmental Policy Act of A federal law enacted January 1, 1970, to ensure that 1969 (NEPA) federal agency decision-making takes environmental factors into consideration. State and local entities must comply with NEPA when they are involved in federal actions (e.g., using federal funding for a project). National Personal Transportation A survey conducted periodically by FHWA to Survey (NPTS) measure travel of American households, focusing primarily on local, repetitive travel. NPTS data are intended to provide insights on travel by trip purpose and mode, social and economic characteristics of the trip makers, changes in vehicle ownership, vehicle and fuel usage, the changing travel patterns of women and minorities, and changes in the mobility of the older driver population. National wetlands inventory (NWI) An inventory of wetlands maintained by the U.S. Fish and Wildlife Service. Databases are available in digital (computer readable) format and are compatible with GIS software. Network An integrated series of road segments that behave as a system. Thus, a change in one road segment often will affect the performance of others. Noise abatement criteria (NAC) Noise levels established by FHWA for a series of activity categories (i.e., land uses). If a proposed project would result in noise levels higher than the NAC, noise abatement measures must be taken. Origin-destination (O-D) pair The passage of traffic originating at one node on the network and traveling to another along a unique path. Office of Solid Waste and The office within U.S. EPA that oversees Emergency Response (OSWER) implementation of most hazardous waste regulations. In response to Executive Order 12898, OSWER has had a policy on environmental justice since 1994. Protective action distance (PAD) The downwind distance from a release that defines a zone in which persons should be either evacuated or sheltered-in-place. Paratransit The use of small buses or vans to provide transit services for transportation-disadvantaged groups, such as people with significant physical disabilities, and 358

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nondrivers who require medical or social services. Paratransit may also include flexible route, door-to- door transit service to the general public. Pass-by traffic Traffic that both originates in, and is destined for, locations outside of the local area in which it is traveling. Pedestrian danger index The number of pedestrian injuries and fatalities in an area of analysis divided by the area's population. This number is then divided by a number representing the overall level of pedestrian activity in the area. Phase 1 environmental site Initial evaluation of a transportation corridor for the assessment (ESA) existence of contaminated sites. The ESA may be undertaken as a portion of the NEPA environmental review, in preparation for property acquisition, or before construction in a right-of-way zone. Photomontage A photo-realism technique in which images of various alternatives are superimposed on an image of the existing environment. It allows respondents to evaluate the positive or negative effects of each project alternative in relation to the existing environment. Price elasticity of demand A measure of consumer response to a change in price calculated by dividing the percentage change in quantity by the percentage change in price. Privacy An issue in sociodemographic data, privacy generally is understood to mean that the information conveyed is not specific (i.e., disaggregate) enough for the attributes of a single household, person, or business to be revealed. To ensure the privacy of individuals, the US. Census Bureau may suppress data when only very small numbers of observations are present. Progressive A project or financing approach in which the cost burden is disproportionately higher for persons with larger incomes or the benefits accrue primarily to persons with lower incomes. See regressive. Property damage only (PDO) crashes Motor vehicle crashes in which there are no fatalities or personal injuries but property is damaged. This property may be the involved vehicle(s) or other property that is struck by a vehicle. 359

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property that is struck by a vehicle. Protected population Groups of people defined by age, disability, gender, religion, class, race, low-income, limited English proficiency, and national origin. Qualitative analysis An approach that involves considering qualities or attributes that do not lend themselves to quantification. It can be applied to assess people's general feelings toward alternatives by evaluating the way they respond to a series of nonmetric indicators, such as aesthetic quality. Quality of life A general way of expressing the presumed ultimate objective of any form of public action. There are numerous dimensions to quality of life, which are valued differently by different people. Among the normally included dimensions are safety, access to opportunity, clean air and water, and social tolerance. Raster A method of coding and storing a graphic image as a pattern of dots. Also known as a bitmap. Regional air quality Air quality in a region or large area. Regression analysis A statistical technique used to assess the extent to which one or more measures are related to a criterion measure. For example, household rent may be affected by a series of attributes of a property. How much each of these attributes affects rent, given the presence of the other attributes, can be assessed using regression analysis. Regressive A project or financing method that results in persons with lower incomes paying a larger share of their income for a project or a project whose benefits largely accrue to those with higher incomes. See progressive. Rent theory A concept that explains how increased access to a location tends to encourage more intensive use of land at that location. Resource Conservation and Recovery The primary goals of the Resource Conservation and Act (RCRA) Recovery Act (RCRA) are to protect human health and the environment from the potential hazards of waste disposal, to conserve energy and natural resources, to reduce the amount of waste generated, 360

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and to ensure that wastes are managed in an environmentally sound manner. Road segment A short portion of a roadway, often a half-mile or so in length, that is the unit of analysis in safety evaluations and in road network models. Roadway geometry Specific design elements of roadways, including number of lanes, lane width, median type and width, length of acceleration and deceleration lanes for on- and off-ramps, curve radii, and roadway alignment. SARA Superfund Amendments and Reauthorization Act of 1986. SAVIAH Small Area Variations in Air Quality and Health. Scale economies Reductions in average costs that come about through increases in the output (i.e., scale) of plants and equipment. Sensitive noise receptor A person or activity that is particularly vulnerable to traffic noise (e.g., hospitals, rest homes, schools, or houses of worship). Sensitivity analysis The process of analyzing how changes in one factor (e.g., population growth assumptions) influence a key outcome such as traffic volume. Often the factor to be varied is the basis for several scenarios. For example, one might construct several scenarios based on different population growth projections. State Implementation Plan (SIP) EPA-approved state plans for the establishment, regulation, and enforcement of air pollution standards. State Transportation Investment A fiscally constrained and prioritized program of Program (STIP) projects to which state and local transportation agencies have committed over a three-year period. A STIP is required to receive federal funding. Projects within metropolitan areas are contained in the relevant TIP and are referenced in the STIP. Stated preference surveys A citizen survey in which respondents are asked to state their preference for one of two attributes at a time. A series of such pair-wise comparisons are made to estimate how people's preferences are ordered. Storm Water Management Module EPA's storm water and wastewater management 361

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(SWMM) modeling package for analyzing urban drainage systems and sanitary sewers. The MIKE-SWMM application provides users with a complete, graphical, easy-to-use interface. TEA-21 Transportation Equity Act for the 21st century, enacted in 1998. Topographically integrated Digital files that contain line and polygon information geographic encoding and referencing representing boundaries of census tracts, block groups, (TIGER) files and blocks, as well as the locations of streets and roads. Toxic by inhalation (TIH) Classes of chemicals that are toxic by inhalation or that produce TIH gases when they react with water (referred to as TIHWA). Toxic Substances Control Act The Toxic Substances Control Act (TSCA) of 1976 (TSCA) was enacted by Congress to give EPA the ability to track the 75,000 industrial chemicals currently produced in, or imported into, the United States. Toxics Release Inventory (TRI) Database of toxic releases in the U.S. compiled from the Superfund Amendments and Reauthorization Act of 1986 (SARA) Title III Section 313 reports. Traffic analysis zone (TAZ) Small geographic areas that represent urban areas in travel simulation models. TAZs are characterized by population, employment, and other factors and are the places where trips begin (i.e., trip producers) or end (i.e., trip attractors). Traffic calming A combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior, and improve conditions for nonmotorized street users. Expected consequences include safer roadways for pedestrians, bicyclists, and neighborhoods in general. Specific road design characteristics include speed bumps and traffic circles. Traffic demand models Models used to calculate changes in travel time between specified origins and destinations that might be the result of transportation projects, such as changes in road capacity. A limitation of these models is that they rarely take into account non-motorized transportation modes. Same as travel demand models. 362

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Traffic noise Any unwanted noise generated from four major sources: tire/pavement interaction, engine noise, exhaust noise, and brakes. Traffic Noise Model (TNM) Noise-prediction software. Developed by FHWA, TNM is the successor to STAMINA and offers clear improvements over it, including modeling for free- flow and stop-and-go traffic conditions. TRANPLAN A set of integrated computer programs that encompass a four-step travel demand model. It operates within a GIS environment. Transportation Analysis and An integrated system of travel forecasting models that Simulation System (TRANSIMS) includes a population synthesizer, activity generator, route planner, and traffic microsimulator. TransCAD A GIS-based computer model that stores, displays, manages, and analyzes transportation data. It has modules for routing and travel demand forecasting. Transportation choice The quantity and quality of transportation options available in a geographic area. Choice is an especially complex issue for those who are economically or physically challenged. Transportation conformity Process of coordinating the transportation planning and air quality planning processes. This conformity is achieved when the TIPs are consistent with SIPs. Transportation demand management Programs designed to maximize the people-moving (TDM) capability of the transportation system by increasing the number of persons in a vehicle or by influencing the time of (or need to) travel. TDM programs must rely on incentives or disincentives to make those shifts in behavior attractive. Transportation disadvantaged People who face significant unmet transportation needs. Transportation Improvement Plan A federally mandated regional transportation (TIP) improvement plan developed by a metropolitan planning organization (MPO). The TIP outlines the staged development of the area's fiscally constrained long-range transportation plan with priority projects identified. 363

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Travel demand (TD) models A series of mathematical equations used to represent how choices are made when people travel. Such models require a series of assumptions, and the parameters in the equations are calibrated to match existing data. The models are used to forecast future travel. Generally, these models have four steps: trip generation, trip distribution, mode split, and traffic assignment. Travel Model Improvement Program A continuing research program to help planning (TMIP) agencies improve their travel analysis techniques. A major product of this program has been the TRansportation ANalysis SIMulation System (TRANSIMS), a new form of travel modeling technology. Travel time variability Uncertainty as to the amount of time a trip will take or the time at which one will arrive. For just-in-time industries or commuters, travel time variability often is as important as average travel time. Triangular irregular network (TIN) A surface representation derived from irregularly spaced sample points and break-line features. Each sample point has an x,y coordinate and a surface, or z- value. These points are connected by edges to form a set of nonoverlapping triangles used to represent the surface. Trip purpose The reason why a trip is made. The purpose of a trip influences the mode used, the time at which the trip is made, the length of the trip, and other trip attributes. Common trip purposes include work and work-related business, shopping, and social/recreational interaction. Underground storage tank (UST) A storage tank designed to contain chemical compounds such as hydrocarbons that is located below ground level. USTs and above-ground storage tanks (ASTs) can be sources of toxic releases. Universal access Transportation facility design that accommodates people with a range of needs, including wheelchair users, people who walk with difficulty or are vulnerable to falls, people who have visual disabilities, and pedestrians who are pushing strollers or handcarts. Urban form The array of land uses and their densities within an urban area. Urban form is influenced by transportation 364

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facilities that affect the relative accessibility of different locations. Urban Transportation Planning A system of analytic tools and methods developed by System (UTPS) the U.S. Department of Transportation in the 1970s to facilitate the four-step travel demand modeling process. See travel demand models. U.S. Environmental Protection EPA's mission is to protect human health and to Agency (U.S. EPA) safeguard the natural environment--air, water, and land. Vehicle hours traveled (VHT) The number of hours spent on a specific road segment or within a road network by the vehicles operating on it per unit of time, generally a day. For a given volume of traffic, higher flow speed (e.g., less congestion) will lead to a reduction in VHT. Vehicle miles traveled (VMT) The number of miles driven by the vehicles using a specific road segment per unit of time, usually a day. VMT is equal to the traffic volume multiplied by the length of the roadway. See AADT. Vehicle operating cost (VOC) The variable cost to vehicle owners of operating these vehicles on roadways per mile of travel. Included in VOC are fuel and oil consumption, wear and tear, depreciation, and insurance. Flow speed, as well as road geometry and other physical attributes, can influence VOC. Vertical equity Equitable distribution of benefits and costs among groups. Groups are usually distinguished by wealth or income. Viewshed An area that can be viewed from a particular site or roadway. Communities may adopt ordinances to reduce the impact of man-made structures and grading on views of existing landscapes and open spaces as seen from public roads. Virtual metropolitan model A model that combines several visual computer models to create a comprehensive virtual model of an entire metropolitan area. Virtual metropolitan models are constructed by combining aerial photographs with street-level imagery and 3-D geometry to produce realistic simulations of large urban environments. 365

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Visual acuity The ability of the eyes to resolve detail. Visual preference survey (VPS) A form of resident survey that allows respondents to express their preferences for certain types of development rather than for specific proposals. Through a series of slides, respondents rate their attitudes regarding images, which are later analyzed to produce a consensus of resident preferences. Volume-to-capacity (V/C) ratio The ratio of the number of vehicles traveling on a roadway to the number that would result in a slowing of traffic to a specified speed. This level of traffic is defined as the effective capacity of the roadway. In general, congestion begins to set in at a V/C ratio of about 0.8. Weighted decibels (dBA) Units of sound that include an adjustment whereby high- and low-pitched sounds are given higher scores. The objective is to approximate the way humans hear sounds. Windshield survey An inventory of land uses and an observation of natural and human environments collected visually, generally by driving through a corridor in which changes are proposed. Wire-frame model A type of visual computer modeling commonly used for proposed transportation projects. Wire-frame models are derived from a continuous series of roadway cross sections that are linked together to form a 3-D model of the proposed roadway design. 366