Glossary of Transportation Terminology
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Acceleration lane
Drivers entering a roadway use this lane to increase speed so that they may safely merge with traffic
Arterial street system
Includes the county and city's major high-capacity roadways
Annual Average Daily Traffic (AADT)
The annual average two-way traffic volume on a roadway during a normal day in a specified year
At grade intersection
An intersection where all roadways join or cross at the same level
Average Daily Traffic (ADT)
The average two-way daily traffic volume for a specified day
Beltway
The freeway that encircles the Las Vegas metropolitan area
Bureau of Land Management (BLM) land
Federally-owned land areas (67% of Nevada is managed by the BLM)
Bus Rapid Transit (BRT)
A modern, high-tech, rail-like bus system (such as CAT) with rapid, convenient, frequent service and quick collection of fares
Bypass
A highway that allows traffic to avoid driving through an urban area
Capacity
The maximum number of vehicles that can safely pass a given point in one hour, on a specific road, under ideal driving conditions
Channelization
The use of traffic markings or islands to direct traffic into certain paths, for instance, a “channelized” intersection directs portions of traffic into a left turn lane through the use of roadway islands or striping that separates the turn lane from traffic going straight
Cloverleaf interchange
An 8-ramp interchange resembling a cloverleaf, (pictured right) in which 4 ramps lie in a diamond roadway configuration, and 4 ramps lie in a cloverleaf configuration; this type of interchange does not require a traffic signal
Club Ride
An RTC-sponsored program that matches carpool partners together
Collector-Distributor roads (“C-D” roads)
These roadways penetrate neighborhoods, connecting arterial streets (see arterial street system) to residential, or local streets
Congestion
This term relates to how the current traffic on a road compares to the amount of traffic a road was designed to handle; a road is considered “congested” if its peak period traffic volume (see peak period) exceeds 80 percent of the intended capacity of the roadway
Controlled access
A roadway where access is limited to interchanges only
Corridor Study
Evaluating a strip or area of land to determine specific traffic, topography, local environment, and other characteristics in order to identify potential ways to improve or enhance the area's transportation system and roadway network
Deceleration Lane
A lane designed to allow traffic to safely decrease speed
Department of Transportation (DOT)
Each state has its own DOT that manages its system of highways and roadways; Nevada 's DOT is commonly referred to as NDOT
Desert Wetlands Park
This wetland area is a habitat for wildlife and a natural filter that improves the quality of water going back to Lake Mead through the Las Vegas wash (see wash); the park is located in the wash south of Sunrise Mountain
Design capacity
The maximum number of passenger vehicles per lane that is intended to pass a certain point during one hour on an average day
Design Hourly Volume (DHV)
The amount of traffic a transportation facility is designed to carry in one hour
Design noise levels
The maximum traffic noise allowed that has an acceptable impact on human activities
Design speed
The maximum speed at which vehicles can travel safely on a highway during ideal traffic conditions
Diamond interchange
The most basic interchange design, shaped like a diamond (pictured right) and consisting of four total ramps (two off ramps and two on ramps); high volume locations usually require traffic signals
Divided highway
A highway where the two travel directions are separated by a barrier
Environmental Impact Study
An analysis of the environmental impacts that proposed transportation projects could potentially have
Environmental Design
Taking into consideration the impact of roadway changes on the local community, aesthetics, ecology, culture, sociology, economics, history, and conservation when planning enhancements, improvements, or other construction related to a roadway network
Expropriation
Acquiring property for highway purposes by the right of eminent domain (see right of eminent domain)
Federal Highway Administration (FHWA)
The branch of the federal DOT (see DOT) that works with state departments to oversee highways in the United States
Feeder streets
These streets allow traffic to circulate within neighborhood areas, taking motorists from smaller local streets (see local streets) to more major arterial streets (see arterial street system)
Flyover ramp
A freeway ramp that “flies over” another roadway in a wide, high curve before merging with traffic on another roadway; the spaghetti bowl ramp linking I-15 north to 95 west is a flyover ramp
Foothills grade separation
The southeast boundary of the corridor study, located on U.S. 93 in Henderson , one mile west of the Railroad Pass Hotel Casino
Freeway
A principal arterial with full control of access (same as highway)
Frontage road
A road adjacent and typically running parallel to a highway, allowing access to nearby properties
Functional classification
The system by which roadways are categorized; a road is grouped into general classes based on its function (see principal arterials, minor arterials, collectors, and local streets)
Grade separation
An intersection with an underpass or overpass that allows traffic to cross over or under another roadway (e.g., the Spaghetti Bowl interchange, pictured right)
High Occupancy Vehicle lane (“HOV” lane)
A lane reserved for vehicles traveling with two or more passengers
Highway
A principal arterial with full control of access (same as freeway)
Infrastructure
Permanent, fixed structures, such as a roadway or railroad tracks
Intelligent Transportation Systems (ITS)
ITS applies current and emerging technologies in information processing, communications, and electronics, to solve transportation problems
Interchange
A system of interconnecting roadways with one or more grade separations (see grade separation)
Intersection
The area at which two or more roadways cross each other
Level of service
A traffic “report card” that rates the flow of traffic on a particular roadway from A (best) to F (worst), by comparing the volume of traffic on the road with its intended maximum capacity
Limited access
A highway that has some access restrictions, but that does not have fully controlled access (see controlled access)
Local streets
Roads that provide direct access to residences
Major arterials
High-volume roadways that provide significant regional access (i.e. Tropicana Avenue )
Metropolitan Planning Organizations (MPOs)
Organizations in major urban areas that are required under the Transportation Equity Act to develop long-term transportation plans for their particular area
Minor arterials
High-volume roads that act as secondary routes or that link to major arterials
National Highway System (NHS)
The system of major roads, interstates, and principal arterials, (pictured right), that connect American cities; these roads receive federal funding
Off-peak (“base”) period
Non-rush periods of the day when travel activity is generally low
Operating speed
The speed a driver travels on a highway under normal conditions
Overpass
A bridge that passes over a freeway or roadway
Peak period
A time period or periods when travel activity is at its heaviest
Peak/base ratio
The number of vehicles traveling during peak periods divided by the number traveling during off-peak periods
Power of condemnation
The ability of NDOT to acquire property as needed to enable construction projects through the right of eminent domain (see right of eminent domain)
Principal arterials
The high-capacity roadways (also called “major arterials”) that make up Nevada 's roadway system, including interstate highways (e.g. I-515)
Projected land use
The anticipated way a specific area will be utilized in the future (e.g., residential, commercial property, industrial use)
Ramp meters
Ramps which control or meter the traffic entering the freeway
Resort corridor
The section of Las Vegas extending south from the Fremont Street area through Las Vegas Boulevard where the major casinos are situated
Right of eminent domain
The right for NDOT or any government entity to acquire property (through the appropriate channels and with appropriate compensation for property owners) as deemed necessary to enable the construction, relocation, or modification of a roadway for the overall public good
Right-of-way (also “R/W”)
(1) Publicly owned land that can be acquired and used for transportation purposes; (2) The right of one vehicle or pedestrian to proceed before another
Roadway
An improved pathway that it intended to be used by motor vehicles
Roadway Network
Includes the major roadways within any specific study area
Regional Transportation Commission (RTC)
The local organization that focuses on the short- and long-term transportation needs related to southern Nevada 's streets, cities, and region
Single-Point Urban Interchange (SPUI)
An interchange (pictured right) where all movements of traffic entering and exiting the freeway are controlled by one traffic signal
Service road
A low-quality road used primarily to transport people or materials needed for utility maintenance in the highway right-of-way
Sound/noise barrier
A wall or other barrier that separates a highway from residential or commercial areas adjacent to the highway with the purpose of reducing roadway noise
Stack interchange
An interchange with several flyover ramps (see flyover ramps)
Staging area
Section of land near a construction site designated for equipment and truck storage, maintenance, and warm up prior to engagement in construction activities
Statewide Transportation Improvement Program (STIP)
A document produced annually by the NDOT with cooperation from federal and regional agencies, local governments, and planning boards, which outlines state transportation projects so that money can be appropriately allocated to fund these projects.
Super arterials
Arterials with limited access (i.e. the Desert Inn super arterial)
Surface street
In an urban area, this is the term used for any street that is not a freeway
Surface Transportation Program (STP)
A system of connectors, major and minor arterial roadways, that are not included in the NHS (see NHS), but may receive some federal funding
Travel Demand Modeling (TDM)
Analysis of spatial and temporal dimensions related to travel patterns, in order to effectively plan the distribution and management of travel demand; an important initial step in the creation of transportation plans such as TIP (see transportation improvement programs)
Traffic modeling
Using a computer program to analyze the prominent ways people travel
Traffic volume
The number of vehicles traveling on a specified roadway during a specific time period, typically reported as “vehicles per hour (vph)” or “vehicles per day (vpd)”
Transportation Improvement Programs (TIP)
A prioritized list of transportation projects prepared annually by regional planning organizations.
Two-directional link volume
The two-way volume of traffic passing through a specific section of roadway between two nodes (e.g., an overpass or intersection) during one hour
Underpass
This is the location where a roadway, railroad, or other feature passes under the freeway
Viaduct
An elevated roadway structure
Volume-to-capacity ratio
The number of vehicles expected to use a roadway during its busiest hour, divided by the intended roadway capacity
Wash, the
The Las Vegas wash (pictured right) is the main channel through which excess surface water from the valley returns to Lake Mead ; the wash stretches 12 miles from the southeast part of the valley to Lake Mead