Glossary
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Threatened Species:
Species defined through the Endangered Species Act as likely to become endangered within the foreseeable future throughout all or a significant portion of its range and published in the Federal Register.
Traffic Analysis Zone (TAZ):
A traffic analysis zone is the unit of geography most commonly used in conventional transportation planning models. The size of a zone varies, but for typical metropolitan planning software, a zone of under 3,000 people is common. The spatial extent of zones typically varies in models, ranging from very large areas in the exurbs to as small as city blocks or buildings in central business districts.
Traffic Analysis Study Area:
An area used in analyses of traffic conditions that includes all major roadways wherein potential transportation improvements to the corridor would affect travel.
Transportation Demand Management (TDM) Alternatives:
Behavioral changes to commuters’ travel habits that result in fewer vehicles during peak hours. Examples would be carpooling/vanpooling, employee trip reduction programs, compressed work weeks, telecommuting, flex-time, and employer incentives.
Transportation System Management (TSM) Alternatives:
Management to make the existing transportation system as efficient as possible. Examples would be park-and-ride lots, ridesharing, HOV facilities, traffic signal coordination, and intersection improvements.
Travel Demand:
The number of users desiring to travel the highway system based on the available roadway network.
Upland Habitat:
Land that has sufficient dry conditions for hydrophytic vegetation, hydric soils, and /or wetland hydrology to be lacking. Any area that is not a wetland, deepwater aquatic habitat, or other special aquatic site is considered upland habitat.
Volume to Capacity (V/C):
Volume to Capacity (V/C): The ratio of current traffic flow rate to capacity of a specified roadway or section of roadway.
Vehicle Hours Traveled (VHT):
The time (in hours) that users spend on the roadway system during a specific time period.
Viewshed:
All land seen from one static point.
Vehicle Miles Traveled:
The measurement of the total miles traveled by all vehicles in a specified area during a specified time.
Watershed:
A specific geographic area drained by a major stream or river.
Wetland (Adjacent):
Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and under normal conditions do support, a prevalence of vegetation typically adapted for life in saturated conditions. Adjacent wetlands also lie within the 100-year floodplain and/or have a hydrologic connection to navigable waters.
Wetland (Isolated):
Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and under normal conditions do support, a prevalence of vegetation typically adapted for life in saturated conditions. Isolated wetlands do not lie within the 100-year floodplain nor do they have a hydrologic connection to navigable waters.
NOTE: For further reference, please consult the TxDOT website at: http://onlinemanuals.txdot.gov/txdotmanuals/ glo/index.htm.
A | B | C | D | E | F | G | H | I | L | M | N | O | P | R | S | T | U | V | W | Acronyms
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