100-Year Flood
(or: One-Hundred-Year Flood)

A flood that has a predicted one percent chance of occurring or being exceeded in a given year (on average, it can be expected to occur once in 100 years). 24 VSA 4303 (8) establishes the 100-year Flood as the Base Flood for the purposes of regulations adopted pursuant to Chapter 117.

Occupancy Permit (Certificate of Occupancy)

A permit, typically issued at the completion of construction but preceding the use or change in use of a property, documenting compliance with all of a community’s land use regulations and building codes and authorizing the owner to use the property for the purposes specified in the permit.

Off Peak

Trips that occur during period of relatively low traffic.

Off-Street Loading

The portion of a lot, building, or structure that is used (or is required to be used) solely for the loading or unloading of trucks, buses, taxis, etc.

Off-Street Parking

The portion of a lot, building, or structure that is used (or is required to be used) solely for vehicular parking (typically also including access lanes).

Official Business Directional Sign

An official Vermont Agency of Transportation designated business directional sign, which includes a legal business name, logo, directional arrow, and mileage from the business. Black OBDS signs indicate businesses, where brown OBDS signs represent recreational areas (brown signs requiring FHWA approval to use). Towns are assessed an installation fee and an annual maintenance fee for each sign.

Official Map

A map officially adopted by a municipality that depicts the location of existing and planned public streets, lands, and structures.


The tendency for rear tires to follow a shorter path than the front tires when turning. This is a primary concern with Trucks, Buses, or trailered vehicles because rear tires may clip street signs, or drive onto shoulders, walkways, or bike lanes, or cross the centerline on a curve, creating a safety hazard for adjacent and oncoming traffic.

Open Space

An area of land that is valued for natural processes and wildlife, for agricultural and sylvan production, for active and passive recreation, and/or for providing other public benefits.

Open Space Function

The functions intended to be provided by Open Space such as supporting 1) Natural Areas, 2) Working Landscapes, and 3) recreation.

Open Space Plan

A municipal plan to guide public and private conservation strategies.

Origin/Destination Study

A study of where person or vehicle trips begin and end. Such a study may also include trip purposes and frequencies.


An aerial photograph that eliminates the distortion produced on the edges of normal aerial photographs caused by the curvature of the earth’s surface.

Overlay Zone (Overlay District)

A Zoning District (with boundaries that may or may not coincide with those of regular zoning districts) used to impose regulations that supplement those of the regular zoning districts.


A colorless gas with a sweet odor that is not a direct emission from transportation sources, but is formed when VOCs and NOx from car exhausts and some industrial emissions combine in the presence of sunlight. Ground-level ozone is associated with smog conditions and initiates damage to lungs, trees, crops and materials. Requlated by the Clean Air Act Amendments of 1990 (CAAA).