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Designing Sidewalks and Trails for Access

Appendix B: Glossary

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Note: This report was published in 2001. Some terms may be obsolete, and some programs may no longer be active. More current information may be available in other reports and guidance; see the US Access Board's reports and guidelines about public rights-of-way at Federal Highway Administration (FHWA) program information is available at

Accessible route - A continuous, unobstructed path connecting all accessible elements and spaces of a building or facility that meets the requirements of ADAAG.

Alteration - Modification made to an existing building or facility that goes beyond normal maintenance activities and affects or could affect usability.

Americans with Disabilities Act of 1990 (ADA) - A Federal law prohibiting discrimination against people with disabilities. Requires public entities and public accommodations to provide accessible accommodations for people with disabilities.

Americans with Disabilities Act Accessibility Guidelines - Provide scoping and technical specifications for new construction and alterations undertaken by entities covered by the ADA.

ANSI A117.1, Making Buildings Accessible to and Usable by the Physically Handicapped - The first American standard developed for accessibility; specifies technical requirements for new construction and alterations.

Approach - The section of the accessible route that flanks the landing of a curb ramp. The approach may be slightly graded if the landing level is below the elevation of the adjoining sidewalk.

Architectural Barriers Act of 1968 (ABA) - A Federal law stating that buildings and facilities designed, constructed, or altered with Federal funds, or leased by a Federal agency, must comply with standards for physical accessibility.

Arterial road - A major through route; arterials often provide direct service between cities and large towns.

Assistive device - A device that assists users in accomplishing day-to-day functions. For example, a wheelchair is an assistive device to assist a person who cannot walk.

Audible warning - A warning consisting of words or sounds indicating a potentially hazardous situation.

Barrier curb - A relatively high and steep-faced curb, designed with the intention of discouraging vehicles from leaving the roadway.
NOTE: This term is no longer used and has been removed from the American Association of State Highway and Transportation Officials A Policy on Geometric Design of Highways and Streets.

Barrier removal - Removal, rearrangement, or modification of objects positioned or structured in a manner that impedes access. Can include rearrangement or removal of furniture or equipment, installation of curb cuts or ramps, or repositioning items such as telephone kiosks or newspaper boxes.

Bevel - A surface that meets another surface at any angle other than 90 degrees.

Bulbout - Another term for a curb extension, which is a section of sidewalk at an intersection or midblock crossing that reduces the crossing width for pedestrians and can help reduce traffic speeds.

Caster - A wheel that can pivot but is not intended to govern the driving direction; typically used for the front wheels of most wheelchairs.

Changes in level - Vertical height transitions between adjacent surfaces or along the surface of a path.

Clear space in crosswalk - The additional space required to be included in a crosswalk at the corner where the ramp of a diagonal curb ramp meets the street so that those entering or exiting the base of the ramp can remain within the crosswalk.

Cognitive disability - Limitation of the ability to perceive, recognize, understand, interpret, and/or respond to information.

Collector road - A roadway linking traffic on local roads to the arterial road network.

Commercial facility - Facilities that are intended for nonresidential use by private entities and whose operation affects commerce.

Community impact assessment - Assessment of the impact of a proposed transportation project on a community; includes informing local residents, businesses, transportation planners, and politicians of the probable positive and negative effects of a project.

Continuous passage - An unobstructed way of pedestrian passage or travel that connects pedestrian areas, elements, and facilities to accessible routes on adjacent sites.

Crosswalk - Portion of a roadway where pedestrians are permitted to cross the street; can be marked or unmarked.

Cross-slope - The slope measured perpendicular to the direction of travel.

Curb extension - A section of sidewalk at an intersection or midblock crossing that reduces the crossing width for pedestrians and that can help reduce traffic speeds.

Curb ramp - A combined ramp and landing that accomplishes a change in level at a curb. This element provides street and sidewalk access to pedestrians using wheelchairs.

Design width - The width specification that a sidewalk or trail was intended to meet, usually set by building codes or agency guidelines.

Detectable warning - A standardized surface feature built in or applied to walking surfaces or other elements to warn visually impaired people of upcoming hazards.

Diagonal curb ramp - A curb ramp positioned at the corner of an intersection.

Diagonal technique - An environmental scanning technique in which a visually disabled person holds a cane in a stationary position diagonally across the body with the cane touching or just above the ground at a point outside one shoulder. This technique is used primarily in familiar, controlled environments.

Drainage bar - A bar made of wood, rubber, or stone placed across a trail to divert runoff across rather than down the trail.

Drainage inlet - A location where water runoff from the street or sidewalk enters the storm drain system; the openings to drainage inlets are typically covered by a grate or other perforated surface to protect pedestrians.

Driveway crossing - A ramp positioned where a driveway and the sidewalk meet; designed to ease the transition between a street and a driveway.

Existing facility - A structure such as a building, site, complex, road, walkway, parking lot, or other real or personal property.

Feasible - Capable of being accomplished with a reasonable amount of effort, cost, or other hardship. With regard to ADA compliance, feasibility is determined on a case-by-case basis. For example, it might not be feasible to install a ramp that meets ADAAG specifications on a very steep hill, but it would be feasible to install an ADAAG ramp at the entrance of a building.

Finished-floor elevation - The elevation at which the building foundation meets the prevailing ground surface.

Flare - A sloped surface that flanks a curb ramp and provides a graded transition between the ramp and the sidewalk. Flares bridge differences in elevation and are intended to prevent ambulatory pedestrians from tripping. Flares are not considered part of the accessible route.

Global Positioning System (GPS) - A system that identifies position and elevation; a hand console is used to obtain data from an orbiting satellite.

Grade - The slope parallel to the direction of travel that is calculated by dividing the vertical change in elevation by the horizontal distance covered.

Grade-separated crossings - Facilities such as overpasses, underpasses, skywalks, or tunnels that allow pedestrians and motor vehicles to cross a street at different levels.

Gutter - A trough or dip used for drainage purposes that runs along the edge of the street and curb or curb ramp.

Hearing impairment - A condition causing partial or total deafness.

Hot response - An instant response to a trigger stimulus, such as a signal change caused by pedestrian-actuated traffic controls at many medians.

Intermodalism - The use of multiple types of transportation to reach one destination; includes combining the use of trains and buses, automobiles, bicycles, and pedestrian transport on a given trip.

Intersection - An area where two or more pathways or roadways join together.

Island - A pedestrian refuge within the right-of-way and traffic lanes of a highway or street; also used as loading stops for light rail or buses.

Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) - Federal legislation authorizing highway, highway safety, transit, and other surface transportation programs from 1991 through 1997. It provided new funding opportunities for sidewalks, shared-use paths, and recreational trails. ISTEA was superseded by the Transportation Equity Act for the 21st Century.

Land management agency - Includes national entities such as the USDA Forest Service and National Park Service, State and local park systems, and private organizations that manage large tracts of land including primitive or wilderness recreation areas.

Landing - A level area of sidewalk at the top of a curb ramp facing the ramp path.

Local road - A road that serves individual residences or businesses and/or distributes traffic within a given urban or rural area.

Long-range transportation plan - A transportation plan developed by States and MPOs to encapsulate 20 years of transportation planning and policy.

Maximum cross-slope - A limited section of a trail or sidewalk that exceeds the typical running cross-slope of the path.

Maximum grade - A limited section of path that exceeds the typical running grade.

Median - An island in the center of a road that provides pedestrians with a place of refuge and reduces the crossing distance between safety points.

Midblock crossing - A crossing point positioned in the center of a block rather than at an intersection.

Minimum clearance width - the narrowest point on a sidewalk or trail.

Mobility impairment - A condition limiting physical ability; generally considered to include lack of a limb or loss of limb use due to disease, amputation, paralysis, injury, or developmental condition; or limitation of movement due to cardiovascular or other disease. Although visual or hearing impairments and cognitive disabilities can hamper ease of travel, people with sensory or cognitive impairments are not termed people with mobility impairments in this report.

Metropolitan Planning Organization (MPO) - A regional transportation planning and policy agency for urban areas with populations larger than 50,000.

New construction - A project in which entirely new facility will be built from the ground up.

Obstacle - An object that limits the vertical passage space, protrudes into the circulation route, or reduces the clearance width of a sidewalk or trail.

Parallel curb ramp - A curb ramp design in which the sidewalk slopes down on either side of a landing; parallel curb ramps require users to turn before entering the street.

Passing space - A section of path wide enough to allow two wheelchair users to pass one another or travel abreast.

Passing space interval - The distance between passing spaces.

Path or pathway - A track or route along which people are intended to travel.

Pedestrian - A person who travels on foot or who uses assistive devices, such as a wheelchair, for mobility.

Pedestrian-actuated traffic control - A push-button or other control operated by pedestrians that is designed to interrupt the prevailing signal cycle to permit pedestrians to cross an intersection.

Pedestrian/Bicycle Coordinator - A position responsible for planning and managing nonmotorized facilities and programs, creating safety and promotional materials encouraging bicycle and pedestrian transportation, and serving as the principal liaison between government transportation entities, the press, citizen organizations, and individuals on bicycling and walking issues.

Perpendicular curb ramp - A curb ramp design in which the ramp path is perpendicular to the edge of the curb.

Places of public accommodation - Facilities operated by private entities that fall within the following 12 broad categories defined by Congress: places of lodging, food establishments, entertainment houses, public gathering centers, sales establishments, service establishments, transportation stations, places of recreation, museums and zoos, social service establishments, and places of education.

Private entity - An individual or organization not employed, owned, or operated by the government.

Program access - Access provided to a program, service, or activity conducted or funded by a public entity.

Prosthesis - An artificial device that replaces part of the body; includes artificial limbs that serve as assistive devices and enable mobility.

Public entity - Any State or local government; department agency, special-purpose district, or other instrumentality of a State or States or local government, and any commuter authority.

Ramp - A sloped transition between two elevation levels.

Rate of cross-slope change - The change in cross-slope over a given distance.

Rate of grade change - The change in grade over a given distance.

Readily achievable - Easily accomplished and able to be carried out without much difficulty or expense; refers to the criterion for barrier removal under Title III of the ADA.

Reasonable accommodation - Modifications or adjustments to a program, work environment, or job description that make it easier for a person with a disability to participate in the same manner as other employees.

Recreation Access Advisory Committee - A committee established in 1993 by the U.S. Access Board to develop recommendations for accessible recreation facilities.

Rehabilitation Act of 1973 - A Federal law requiring nondiscrimination in the employment practices of Federal agencies of the executive branch and Federal contractors; requires all Federally assisted programs, services, and activities to be available to people with disabilities.

Rest area - A level portion of a trail that is wide enough to provide wheelchair users and others a place to rest and gain relief from prevailing grade and cross-slope demands.

Rest area interval - The distance between rest areas.

Right-of-way - Real property rights (whether by fee-simple ownership, by easement, or by other agreement) acquired across land for a purpose, including pedestrian use.

Running cross-slope - The average cross-slope of a contiguous section of a sidewalk or trail.

Running grade - The average of many short, contiguous grades.

Rural - Areas outside the boundaries of urban areas.

Scoping specifications - Describes where accessibility is appropriate, when it is required, and how many aspects of a building, facility, or site must be accessible.

Section 14 (1994) - Proposed accessibility guidelines for public rights-of-way (now reserved).

Section 504 - The section of the Rehabilitation Act that prohibits discrimination by any program or activity conducted by the Federal government.

Sensory deficit - Impairment of one of the five senses; includes partial or complete loss of hearing or vision, color blindness, loss of sensation in some part of the body or the loss of the sense of balance.

Shared-use path - A trail that permits more than one type of user, such as a trail designated for use by both pedestrians and bicyclists.

Shy distance - The area along the sidewalk closest to buildings, retaining walls, curbs, and fences generally avoided by pedestrians.

Sidewalk - The portion of a highway, road, or street intended for pedestrians.

Sight distance - The length of roadway visible to a driver or pedestrian; the distance a person can see along an unobstructed line of sight.

Site infeasibility - Existing site development conditions that prohibit the incorporation of elements, spaces, or features that are in full and strict compliance with the minimum requirements for new construction and that are necessary for pedestrian access, circulation, and use.

Structural impracticability - Changes having little likelihood of being accomplished without removing or altering a load-bearing structural member and/or incurring an increased cost of 50 percent or more of the value of the element of the building or facility involved.

Surface Transportation Program (STP) - A Federal program that provides grants to States for federally funded roadways and enhancement projects.

Suburban - Refers to an area surrounding a city that is closely settled.

Switchback - A trail or road that ascends a steep incline by taking a winding course to reduce the grade of the path.

Tactile warning - A change in surface condition that provides a tactile cue to alert pedestrians of a hazardous situation.

Technical specifications - Design and installation requirements.

Technically infeasible - A situation that prevents full compliance with ADAAG because existing structural conditions would require removing or altering a load bearing member that is an essential part of the structural frame; or because other existing physical or site constraints prohibit modification or addition of elements, spaces, or features that are in full and strict compliance with the minimum requirements for new construction and that are necessary to provide accessibility.

Title II of the Americans with Disabilities Act of 1990 - The section of the Americans with Disabilities Act of 1990 that prohibits State and local governments from discriminating against people with disabilities in programs, services, and activities.

Title III of the Americans with Disabilities Act of 1990 - The section of the Americans with Disabilities Act of 1990 that prohibits places of public accommodation and commercial facilities from discriminating on the basis of disability.

Touch technique - An environmental scanning method in which a blind person arcs a cane from side to side and touches points outside both shoulders. Used primarily in unfamiliar or changing environments, such as on sidewalks and streets.

Trail - A path of travel for recreation and/or transportation within a park, natural environment, or designated corridor that is not classified as a highway, road, or street.

Transportation agency - A Federal, State, or local government entity responsible for planning and designing transportation systems and facilities for a particular jurisdiction.

Transportation Enhancement - Projects that include providing bicycle and pedestrian facilities; converting abandoned railroad rights-of-way into trails; preserving historic transportation sites; acquiring scenic easements; mitigating the negative impacts of a project on a community by providing additional benefits; and other projects.

Transportation Enhancement Coordinator - A position that manages transportation enhancement programs for State departments of transportation.

Transportation Equity Act for the 21st Century (TEA-21) - Federal legislation authorizing highway, highway safety, transit, and other surface transportation programs from 1998 through 2003. It provides funding opportunities for pedestrian, bicycling, and public transit facilities and emphasizes intermodalism, multimodalism, and community participation in transportation planning initiated by ISTEA.

Transportation Improvement Program or Statewide Transportation Improvement Plan (TIP or STIP) - A transportation plan that encapsulates planning and policy for a minimum of 3 years. Includes a prioritized list of all projects that will be constructed with Federal transportation funding.

Truncated domes - Small domes with flattened tops that are used as tactile warnings at transit platforms and curb edges.

Uniform Federal Accessibility Standards - Accessibility standards that all Federal agencies are required to meet; includes scoping and technical specifications.

Urban - Refers to places within boundaries set by State and local officials that have a population of 50,000 or more. Urban areas are more densely populated and contain a higher density of built structures.

U.S. Access Board (United States Architectural and Transportation Barriers Compliance Board) - A Federal agency that is responsible for developing Federal accessibility guidelines under the ADA and other laws.

Vertical clearance - The minimum unobstructed vertical passage space required along a sidewalk or trail.

Visual impairment - Loss or partial loss of vision.

Visual warning - The use of contrasting surface colors to indicate a change in environment, such as at a curb ramp where the sidewalk changes to the street.

Wilderness Act of 1964 - A Federal law that prohibits the use of motorized vehicles and mechanized construction on certain tracts of federally managed land.

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Updated: 1/31/2017
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