Transportation Glossary

The following is a listing of transportation-related terminology and phraseology developed by CCMPO.
Click here to view a list of Acronyms only...

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Term	Acronym	Definition
Hazardous Material	HAZMAT	Classified by the U.S. Environmental Protection Agency (EPA), transport of HAZMAT is regulated by the U.S. Department of Transportation.
Headway		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	HAL	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 Occupancy Vehicle	HOV	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	HRRR	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).
High Speed Rail	HSR	Intercity passenger rail service that is reasonably expected to reach speeds of at least 110 miles per hour (49 U.S.C. §26105 (b)(4)).
Highway Capacity Manual	HCM	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 Performance Monitoring System	HPMS	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	HSIP	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	HTF	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.
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.
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.
Hydrocarbons	HC	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).

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