Glossary & Acronyms

Provided below is a listing of commonly used technical terms that are used to describe the I-15 North Corridor Project.

• Arterial – a major roadway in a city or urban area that collects traffic and may be connected to the freeway system. Some examples in the I-15 North Corridor project area include Washington Avenue , Lake Mead Boulevard , and Craig Road .

• Auxiliary Lanes – the far right traffic lanes of a freeway that connect the entrance ramps at one interchange to the next exit ramps. Auxiliary lanes help reduce slowdowns as well as improve safety when entering and exiting vehicles merge.

• Beltway – a freeway that partially or completely encircles a metropolitan area. An example is the Las Vegas Beltway (I-215) which is currently being constructed around the Las Vegas metropolitan area.

• Capacity – the maximum flow rate at which vehicles can be expected to move on a given roadway segment, measured in vehicles per hour or passenger cars per hour.

• Collector-Distributor Road – freeway traffic lanes on the far right that are physically separated from thru traffic lanes for the purpose of providing access to and from the freeway. Collector–distributor roads provide better flow for the thru traffic by separating them from the friction caused by merging and weaving vehicles at entrance ramps and exit ramps.

• Demand – the number of users desiring service on the highway system, measured in vehicles per hour or passenger cars per hour.

• Diamond Interchange – the most basic interchange design, usually consisting of four ramps (two off-ramps and two on-ramps). Diamond interchanges have a diamond shape when viewed from the air. Examples in the I-15 North Corridor project area include the Speedway Boulevard interchange and the Apex interchange.

• Environmental Assessment (EA) – a public document produced as part of the federal National Environmental Policy Act (NEPA) process that examines the significance of impacts of transportation projects in order to determine whether an Environmental Impact Statement (EIS) is necessary.

• Environmental Impact Statement (EIS) – a public document produced as part of the NEPA process required for “major Federal actions that significantly affect the quality of the human environment,” {NEPA Section 102 (c)} to inform decision makers and the public of the proposed action, reasonable alternatives, and their environmental impacts.

• Federal Highway Administration (FHWA) – the branch of the federal Department of Transportation that oversees the national highway system. The FHWA works with the Nevada department of transportation to carry out federal initiatives.

• FONSI – a Finding of Non-Significant Impact, or FONSI, is a public document by a federal agency under NEPA that briefly presents the reasons why an action, not otherwise excluded, will not have a significant effect on the human environment and for which an EIS therefore will not be prepared.

• Freeway – a controlled-access, divided highway.

• High Occupancy Vehicle (HOV) Lane – also known as carpool lanes, HOV lanes are lanes reserved for vehicles with two or more occupants. Usually, the HOV lane is the designated far left lane of the freeway. HOV

• Interchange – the junction of a freeway and another road used to provide access control.

• Interstate Highway System – created by Congress in 1956, the National System of Defense and Interstate Highways is a network of superhighways connecting all metropolitan areas within the United States . I-15 is part of that network.

• Level of Service (LOS) – a term used by transportation engineers to indicate that traffic is moving at ideal, average, or poor efficiency and measured on a grade scale of “A” through “F”.

• Merge – a traffic movement in which two separate lanes of traffic combine to form a single lane.

• NDOT – the Nevada Department of Transportation, which manages the network of highways within the state.

• NEPA – the National Environmental Policy Act, established by Congress in 1969, requires a federal agency to document the environmental impact of its actions including an evaluation of alternatives.

• Off-ramp – also called an exit ramp, this is a roadway segment of one or two lanes used by traffic to move from the freeway to the surface streets.

• On-ramp - also called an entrance ramp, this is a roadway segment of one or two lanes used by traffic to move from the surface streets to the freeway.

• Ramp Meter – a traffic signal that controls the entry of vehicles from a ramp onto a freeway. Ramp meters control the frequency and spacing of merging vehicles, which helps to improve the traffic flow.

• Right-of-Way (R/W) – the land owned by NDOT for the purpose of operating and maintaining a highway.

• Regional Transportation Commission (RTC) – Regional Transportation Commission of Southern Nevada, the regional government agency responsible for coordinating and planning transportation activities and projects in the Las Vegas region.

• Shoulder – a portion of the roadway at the outside or inside of the traffic lanes for accommodation of stopped vehicles and emergency use.

• Single Point Urban Interchange(SPUI) - an interchange design similar to the diamond interchange, but with all ramps controlled by a single set of traffic signals. An example in the I-15 North Corridor project area is the Cheyenne Avenue interchange.

• Sound Wall – a wall separating the highway from adjacent residential or commercial areas for the purpose of reducing roadway noise.

• Surface Streets – in an urban area, this term is used to denote all streets and roads other than the freeway.

• Transportation Demand Management (TDM) – a general term for actions that encourage a decrease in the demand for the existing transportation system.

• Weaving – the crossing of two or more traffic streams traveling in the same direction. For example, weaving occurs when an interchange entrance ramp is followed by an exit ramp.