National Ambient Air Quality Standards

Federal air quality standards established pursuant to Section 109 of the Clean Air Act that apply to ambient air quality designed to protect public health. Included are standards for carbon monoxide (CO), lead (Pb), nitrogen dioxide (NO2), ozone (O3), particulate matter (PM-10), and sulfur dioxide (SO2).

National Environmental Policy Act of 1969 (NEPA)

The National Environmental Policy Act of 1969 (NEPA), established a national environmental policy requiring that any project using federal funding or requiring federal approval, including transportation projects, examine the effects of proposed and alternative choices on the environment before a federal decision is made.

National Highway System (NHS)

Approximately 160,000 miles (256,000 kilometers) of roadway important to the nation's economy, defense and mobility. The NHS includes Interstate highways and other major roadways, the Department of Defense's Strategic Highway Network (STRAHNET) and major connectors to military installations and intermodal facilities.

National ITS Architecture

A common, established framework for developing integrated transportation systems, now known as the Architecture Reference for Cooperative and Intelligent Transportation (ARC-IT). ARC-IT is comprised of the communications, enterprise, functional, and physical views which satisfy a defined set of needs. The National ITS Architecture is maintained by the United States Department of Transportation (USDOT).

National Program Plan

Jointly developed by US DOT and ITS America with substantial involvement from the broader ITS community. The purpose of the National Program Plan was to guide the development and deployment of ITS. It defined the first 29 user services and their corresponding user service requirements.


A demand for a mobility improvement that has been identified on the basis of accepted and adopted standards and other assumptions (e.g., land use) and documented in a formal long range or master plan.

Network Slicing

A mechanism that could be used by operators to support multiple "virtual" networks behind the air interface (or, more likely, multiple air interfaces) across the fixed part of the mobile operator's network, both backhaul and core. Network slicing could allow "networks as a service," where the virtual network or slice has performance characteristics such as integrity, reliability, latency that map to user needs, and are a subset of characteristics available to the 5G network.


The property whereby a protocol data unit (PDU) is constructed in such a way that the PDU sender cannot effectively deny having been the sender of that PDU; and the PDU receiver cannot effectively deny having received a particular PDU.