Real-Time System Management Information Program Data Exchange Format Specification — Implementation Guidance
This document is a guide on how to use the Data Exchange Format Specification (DXFS) for specifying implementation of Real-Time System Management Information Program (RTSMIP) at a state or regional level. The background below explains the context under which RTSMIPs are developed. The following section explains the nature and scope of the DXFS.
Section 1201 of the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU), published in August 2005, instructed the Secretary of Transportation to “…establish a real-time system management information program (RTSMIP) to provide, in all states, the capability to monitor, in real-time, the traffic and travel conditions of the major highways of the United States and to share that information to improve the security of the surface transportation system, to address congestion problems, to support improved response to weather events and surface transportation incidents, and facilitate national and regional highway traveler information.”
A Final Rule was published on November 8, 2010, establishing the provisions and parameters for the Real-Time System Management Information Program to be established by State DOTs, other responsible agencies, and partnerships with other commercial entities. The Program is to be established on all Interstate routes within 4 years (November 8, 2014) and on other significant roadways as identified by the States and local agencies within 6 years (November 8, 2016).
In response to these requirements, U.S. Code of Federal Regulations (CFR) 23 Part 511 was developed. 23 CFR Part 511 requires each state to establish and operate a RTSMIP as part of its Intelligent Transportation System (ITS). Title 23 CFR 511 does not require the dissemination of real-time information in any particular manner, only that the states make the information available. It also does not require states to apply any particular technology, technology-dependent application, or business model for collecting, processing and disseminating information. As a result, development of a DXFS and implementation guidance was initiated to support the need of states for a specification that satisfies the essential elements of the rule.
Title 23 CFR 511 requires that real-time information programs be capable of gathering and making available the data for traffic and travel conditions.
The DXFS specification and additional information about Section 1201 is available. (Real-Time System Management Information Program – FHWA Operations.)
It is recommended that this document be used side-by-side or with a copy of the DXFS specification handily available.
1.2 Data Exchange Format Specification (DXFS)
1.2.1 Objectives of the DXFS
Section 1201 required the Secretary to establish data exchange formats to ensure that the data provided by highway and transit monitoring systems, including statewide incident reporting systems, can readily be exchanged across jurisdictional boundaries; facilitating nationwide availability of information. In 2011, U.S. DOT began development of the Data Exchange Format Specification (DXFS) to facilitate the development of interoperable real-time traffic and travel information between public agencies, with other public agencies, and with private entities.
The objective of the DXFS is to create a standards-based definition of key RTSMIP interfaces. This approach addresses three major issues that threaten center to center exchanges of real-time information:
- More than one standard (as well as proprietary solutions) may exist to encode and define the same information. For example incident information could be defined by data concepts from Traffic Management Data Dictionary (TMDD) or from IEEE 1512-Standard for Common Incident Management Message Sets for use by Emergency Management Centers. An agreement must be reached between each pair of agencies or regionally as to what encoding, meaning (derivation), and logical relationships are to be used to describe the information for information exchanges to be effective.
- Each agency may have its own goals and objectives for the data it collects, and the data quality attributes (metadata) will likely be adjusted to meet the intended local uses of the data. Data with inadequate quality attributes may be of little or no value to agencies in other regions. There is no agency/entity expectation as to data quality received from other entities, nor is there a uniformly accepted method for representing data quality (metadata).
- There may be competing methods for communicating encoded transportation information between entities. While today structured implementations of XML are popular over the Internet, there are still organizations that have substantial investments in ASN.1.
The RTSMIP DXFS was developed to eliminate all the above uncertainties and thus measurably accelerate the investment in and deployment of ITS systems that can share real-time traffic and travel conditions information effectively between public entities, or between public and private entities. The RTSMIP DXFS has been developed with consideration of the many stakeholders’ independent goals and objectives. A systems engineering process of verification and especially validation at each key stage of the RTSMIP DXFS development was employed to achieve this stakeholder focused result.
1.2.2 Scope of the DXFS
The DXFS is a detailed specification of the key interfaces defined as part of the RTSMIP (which are discussed in Section 2.3). The DXFS is not a new ITS standard; rather it is a specification of existing ITS standards that can address a set of user needs which support a RTSMIP. For example the existing ITS standard Traffic Management Data Dictionary (TMDD) is specified by the DXFS to address many of the needs/ requirements relevant to providing RTSMIP. As discussed in the previous section, the DXFS is meant to remove uncertainty regarding which standard to apply to a specific interface, facilitating national interoperability in providing data to support RTSMIP.
The Scope of the DXFS is the set of interfaces used to send traffic, transit, and traveler information from one agency to another. The provision of this data directly to travelers is not part of the scope of the specification. While the DXFS covers all the information defined in Rule 23 CFR 511, the scope of the DXFS has been expanded beyond the information defined in the rule to include transit information and additional traffic information that is relevant to the exchange of data between agencies (and other parties). The DXFS is an information level specification, meaning that it defines a set of data concepts (dialogs, messages, data frames and data elements) that can be used to exchange data on an interface. The DXFS does not specify communication protocols, but it does refer to existing standardized protocols that can be used for transferring the data.
1.3 Scope of the DXFS Implementation Guide
The objective of the DXFS Implementation Guide is to provide guidance to public agencies and private organizations on how to use the DXFS. This document provides a guide to using the DXFS to specify an implementation. The intent of the Guide is to provide recommendations for how to move toward full implementation of Data Exchange Formats.
1.4 Users of the DXFS Implementation Guide
The DXFS Implementation Guide has been developed to assist the following groups of users in specifying and then developing an RTSMIP implementation:
- Transportation agency. This group includes state DOTs and regional transportation related organizations (e.g., a municipal DOT or Public Works or a transit agency) that are developing systems that implement aspects of the RTSMIP.
- Public safety agency. This group includes state, county, or local public safety agencies that develop systems that support RTSMIP.
- Traveler information organizations (public or private). This group includes providers of traveler information whether public or private that are involved in the development of systems that support RTSMIP.
- Development contractors. This group includes contractors who have been hired by a transportation or public safety agencies to develop procurement packages that would specify aspects of RTSMIP, or contractors who have been selected to perform the development of RTSMIP related projects.
1.5 Document Organization and Use
This document is organized into 6 sections.
- Section 1: Introduction. This section provides introductory and background information about SAFETEA-LU Section 1201, the Real Time System Management Information Program (RTSMIP), and the Data Exchange Format Specification (DXFS).
- Section 2: User Needs Identification. This section provides summary background information from the Concept of Operations in the DXFS document as well as summary of user needs from the DXFS Concept of Operations. It also starts an example that is followed throughout the remaining sections of the guidance document to describe how to tailor the DXFS to satisfy regional needs from user needs identification to testing.
- Section 3: Requirements Identification. This section provides summary background information from the Requirements section of the DXFS document. This section next provides guidance on how to use the Needs to Requirements Traceability Matrix to identify requirements from DXFS to define information exchanges between centers, including private agencies. Finally the example is continued the with mapping of needs to requirements.
- Section 4: System Design Reference. This section provides summary background information from the Design Reference section of the DXFS document. The section next provides guidance on how to trace into and document the design sections of existing standards to build DXFS dialogs and messages. Finally, the example is continued with the mapping of requirements to design concepts.
- Section 5: Implementation Issues. This section discusses the two key center-to-center standards, NTCIP 2304 and NTCIP 2306, used to describe how to encode and transport information messages, and provides a discussion of technical issues relevant to deployment of a DXFS-based system interface.
- Section 6: Testing. This section provides guidance on DXFS system interface testing, and includes information on how to develop test documentation. This section also completes an example started in Section 3.
The goal of this implementation guide is to explain the suggested process the user should follow in using the DXFS. The suggested process, which will be expanded upon in each of the following sections is shown in Figure 1.
Figure 1. Diagram. Suggested Process for using the DXFS.
(Source: Consensus Systems Technologies.)