The physical and biological environment that a community of a plant or animal species requires to remain viable.

Hazard Area

24 VSA 4303 (8) (C): Land subject to landslides, soil erosion, earthquakes, water supply contamination, or other natural or human-made hazards as identified within a local mitigation plan in conformance with and approved pursuant to the provisions of 44 C.F.R. 201.6.

Hazardous Material

Classified by the U.S. Environmental Protection Agency (EPA), transport of HAZMAT is regulated by the U.S. Department of Transportation.

Hazardous Waste

10 VSA 6602 (4): Any waste or combination of wastes that the ANR Secretary has determined may (1) cause or contribute to an increase in serious irreversible or incapacitating reversible illness, (2) cause or contribute to adverse acute or chronic effects on the health of persons or other living organisms, or (3) have an unusually destructive effect on water quality if discharged to the State’s ground or surface waters.


Often used in context of transit service, “Headway” refers to the time interval between buses or passenger trains moving towards a specific destination or transit-stop along a particular route.

Heavy Rail

Rapid rail transit service using rail cars powered by electricity drawn from a third rail and usually operated on exclusive rights-of-way. It usually uses longer trains and has longer spacing between stations than light rail. (For example, the New York City subway system).

High Accident Location

A location on the federal-aid highway system that has experienced a minimum of five accidents over a five-year period and has an Actual Rate to Critical Rate Ratio (ARCR) of 1 or greater. The list of HALs is maintained by the Vermont Agency of Transportation – Highway Research Section.

High-Intensity Activated Crosswalk

A pedestrian-activated beacon located on the roadside and on mast arms over major approaches to an intersection. The HAWK head consists of two red lenses over a single yellow lens. It displays a red indication to drivers when activated, which creates a gap for pedestrians to use to cross a major roadway.

High Occupancy Vehicle

Vehicle carrying two or more people (i.e. a carpool). Roads may have lanes solely for HOV use, such as carpools, vanpools, and buses.

High Risk Rural Roads Program

A federal safety and funding provision addressing the high fatality and incapacitating injury rate, which occurs on rural roads (nationally, about 60% occur on Rural Major & Minor Collectors, as well as Rural Local Access roads).

Highest & Best Use

The type and intensity of lawful land use for a particular property that provides the maximum profit to the owner.

Highway Capacity Manual

Published by the Transportation Research Board (TRB), the HCM outlines fundamental information and computational techniques on the quality of service and capacity of highway facilities.

Highway Commercial

Land Uses that rely on relatively high traffic volumes as a source of patrons (rather than, for example, relying on a nearby residential area for customers). It also refers to an area (such as a zoning district) intended to provide for highway commercial land uses, typically extending in a relatively narrow strip along the sides of a highway.

Highway Performance Monitoring System

A GIS-based national highway information system that includes data on the extent, condition, performance, use, and operating characteristics of US highways.

Highway Safety Improvement Program

Federal program assisting states to achieve a significant reduction in traffic fatalities and serious injuries on all public roads through the implementation of infrastructure-related highway safety improvements.

Highway Trust Fund

A financing mechanism established under federal law to account for tax receipts (primarily from motor fuel taxes) collected by the federal government and dedicated to surface transportation projects.

Historic Preservation

The research, protection, restoration and rehabilitation of buildings, structures, objects, districts, areas, and sites significant in the history, architecture, archaeology or culture of this state, its communities or the nation (22 VSA 701 (5)).

Historic Preservation Commission

An Advisory Commission established pursuant to 24 VSA 4433 (3) to assist in a municipality’s historic preservation efforts.

Historic Property or Resource

Any building, structure, object, district, area or site that is significant in the history, architecture, archaeology or culture of this State, its communities, or the nation (22 VSA 701 (6)).

Home-Based Trip

A trip that starts and/or ends at home.

Home-Based Work Trip

A trip with one end at work and the other at home.

Home Occupation

An activity carried out for commercial gain by a resident conducted as an Accessory Use in the resident’s dwelling unit.

Hot Spot

A location with higher-than-ambient levels of pollution. Hot spots may be attributed to such things as weather patterns, topography, and traffic intensity.


One or more people who occupy a single Dwelling Unit.

Housing Commission

An Advisory Commission established pursuant to 24 VSA 4433(5).

Housing Unit

One or more rooms, intended to be occupied by a household as separate living quarters containing cooking, sleeping, and sanitary facilities.


Hydrocarbons are a Volatile Organic Compound (VOC) that is released into the atmosphere because of incomplete combustion of petroleum fuels or by their evaporation. The strong odor of diesel fuel is associated with HC. The EPA states that 47% of Hydrocarbon emissions in our atmosphere can be attributed to vehicles. Hydrocarbons combined with Nitrogen Oxides, and sunlight form Ozone (O3).