ITS Standards Program

ITS Standards Advisories provide the ITS transportation community with information and guidance on the consideration and use of ITS standards.

C2F Background

Relevance to U.S. DOT Research Initiatives, the National ITS Architecture, and the National Congestion Initiative

U.S. DOT Research Initiatives

C2F communications support the following U.S. DOT research initiatives:

• Integrated Corridor Management Systems (ICMS)
• Nationwide Surface Transportation Weather Observing and Forecasting System (Clarus)

National ITS Architecture

The National Transportation Communications for ITS Protocol (NTCIP) center-to-field (C2F) communications standards are common across all C2F interfaces in the National ITS Architecture.

National Strategy to Reduce Congestion on America's Transportation Network

The NTCIP C2F communication standards will contribute to the implementation of new congestion-relief strategies and will be key to the deployment of new operational technologies and practices that end traffic tie-ups and of new interstate "corridors of the future," as called for in the National Initiative: National Strategy to Reduce Congestion on America's Transportation Network.

C2F communications are intelligent transportation systems (ITS) communications that take place between a traffic management center (TMC) and one or multiple field devices managed by that center; for example, the communications protocols over which a time-clock-update broadcast message intended for all devices is sent. Most applications of this type involve a computer at a TMC communicating with various devices at the roadside. In particular, the current NTCIP C2F communications profile standards cover the lower layer (below the device message or object) interfaces between a TMC and dynamic message signs (DMS), traffic signals, ramp meters, environmental sensor stations (ESS), closed circuit television (CCTV) cameras, data and data-collection monitoring devices, and other field equipment under the center's control.

NTCIP C2F standards can be divided into two categories: (1) the vocabulary and message content, and (2) the rules for exchanging the messages and data. This ITS standards advisory focuses on the latter category, which we will refer to as NTCIP C2F communications profile standards. Other ITS standards define the former category, specific vocabulary and message content, and cover global object definitions, object definitions for DMS and ESS, and data element definitions for transportation sensor systems (TSS). The two categories of standards work together to exchange meaningful ITS-related information for NTCIP C2F communications. (There are different standards for center-to-center [C2C] communications.)

This advisory varies slightly from prior advisories in that it addresses a larger number of ITS standards spanning a broad spectrum of information transport for standardized messages, thus requiring discussion at varying levels of abstraction. Some topics are covered at a high level of detail, while others are covered at a lower level to differentiate alternatives. The document should be considered as a foundational advisory, to be used in conjunction with specific device advisories (e.g., DMS, ESS), which provide advice on how the devices utilize these lower-level standards.

Consensus-based working groups from the American Association of State Highway and Transportation Officials (AASHTO), the Institute of Transportation Engineers (ITE), and the National Electrical Manufacturers Association (NEMA) were tasked with developing a set of underlying C2F communications standards for the transportation community, the National Transportation Communications for ITS Protocol (NTCIP) standards. NTCIP organizes its standards with use of a layered approach as shown in Figure 1, similar to the International Organization for Standardization (ISO) Open Systems Interconnection (OSI) framework model and the Internet model as defined by the Internet Engineering Task Force (IETF). While message and data standards address the Information Level, NTCIP C2F communications standards primarily address the Applications, Transport, and Subnetwork Levels, although several NTCIP standards are used to encode (i.e., compress) data at the Information Level. At these levels, NTCIP leverages existing computer and telecommunications-industry base standards, differentiating between what is mandatory and where alternatives are available what is optional. In some cases, NTCIP standards have extended the industry base standard to meet the specific needs of the transportation community. In this manner, the NTCIP C2F communications standards are "profiles" of base standards and other standards.

back to top

C2F Standards Framework