Telecommunications infrastructure is important in enabling Intelligent Transportation Systems (ITS) to function, as it ties together and moves data between the major elements of an ITS, including roadside equipment, vehicles, the vehicle operator and central operations facilities (such as transportation management centers). Through integrating the individual elements of an ITS, telecommunications provides a critical technical function to the system, and can act as a mechanism for enhancing overall transportation efficiency. Telecommunications also comprises a significant share of the cost of an ITS, both in terms of implementation and operations and maintenance.
Arriving at the telecommunications solution that best suits agencies' needs is a high priority, but it can be a challenge. This is largely due to the rapid pace of change in telecommunications and the skills required to understand and assess different telecommunications alternatives. This report is designed to provide assistance on what processes work best and what factors should be considered when making telecommunications decisions. A number of the best techniques for exploring telecommunications alternatives are presented to help agencies determine the optimal alternative in support of their ITS program.
For this study, the telecommunications experiences of state Departments of Transportation (DOTs) and agencies from across the country were examined. In particular, examples of successful practices in ITS telecommunications were drawn from California, Georgia, Maryland, Michigan, Minnesota, Missouri, New York, Texas, Virginia, and Wisconsin.
An effective needs assessment is important to selecting an appropriate telecommunications solution for an ITS deployment. In addition to a requirements analysis, a needs assessment also includes the use of a state or regional ITS architecture and the development of a telecommunications architecture.
A regional ITS architecture is used to help define the telecommunications requirements of an ITS deployment. By identifying types, volumes, sources, and users of transportation information, the regional ITS architecture helps in understanding connectivity and bandwidth needs, as well as the nature of the communication flow (periodic, continuous, random). A regional ITS architecture progresses from defining the highest level of needs to the specifics of data elements and data flows, and the standards which may be applicable. ** See NOTE
The report describes a number of steps required in developing a regional ITS architecture. These are presented below as a set of lessons learned.
- Gather inputs from stakeholders and obtain consensus on the outcome of the architecture. In developing the regional ITS architecture, stakeholders should provide information on their needs and priorities, discuss their respective roles and responsibilities in transportation management, identify resources operated by them, and define opportunities for sharing information. This process can foster opportunities for partnerships, and through sharing of roles and taking advantage of resources owned (or activities already performed), agencies may benefit from improved performance and lower cost.
- Conduct a user services analysis and develop a Concept of Operations. As part of the architecture development, agencies must identify the ITS user services which satisfy the user needs outlined in the transportation planning process. This is followed by the development of the Concept of Operations, a document that describes the roles and responsibilities of different stakeholders, as well as how their systems will interact in the broader transportation management context.
- Construct the logical architecture. The logical architecture outlines the functional processes necessary to deliver the identified user services. The logical architecture provides a clearly defined specification for each process (by identifying the information which each process uses, stores or generates), a data flow diagram of the information moving between processes, and a data dictionary of the data elements themselves.
- Construct the physical architecture. The physical architecture identifies the physical entities where functions may be performed (such as a traffic operations center or a freeway operations center), as well as the subsystems that belong within each physical entity. Furthermore, it identifies the interconnections between the subsystems and the standards that are appropriate for those interconnections. In analyzing the subsystem interconnections, the physical architecture recognizes the nature of the telecommunications that are needed for the system to be deployed.
- Consult available resources. There are a number of useful tools available for developing a regional ITS architecture. The National ITS Architecture (available online and on CD-ROM) provides a list of the elements at each step in the process, from which those appropriate to the region’s architecture can be selected. The USDOT also has produced a product, "Turbo Architecture" to assist agencies in the efficient development of regional architectures, and there are USDOT courses and training materials available.
In addition, a telecommunications ITS architecture provides a picture of the geographic distribution of the needs, the size and type of the needs, and a view of the layout of the network. Through the network topology, the agency is able to identify both the network routing and the points of interconnection (nodes). Some of the key benefits of a telecommunications ITS architecture include:
- Provides a comprehensive view of the telecommunications needs for a project or regional ITS program.
- Assists in understanding budgeting and project scheduling requirements by providing a geographic layout of the system.
- Provides information to those assessing the suitability of specific equipment to the system’s needs.
- Assists the agency in determining where multiple, dispersed needs may be cost effectively combined.
- Provides information to those who may benefit from either interconnecting to the ITS telecommunications network or utilizing the network’s resources.
- Provides a view of the network to assist in planning for network growth.
The Southern California ITS Showcase provides an example of a telecommunications ITS architecture. The Showcase includes 17 projects distributed across four California Department of Transportation (Caltrans) Districts. Systems from over a dozen agencies are included in or interconnected with the Showcase. Each system converses with its peers through a "seed" which performs translation. Seeds are connected to a regional "kernel" which provides routing, network management, security, and other shared network services. Kernels are also interconnected via the Showcase's primary network connections. Each District also contains a TMC co-owned and operated by Caltrans and the California Highway Patrol. The TMCs are also interconnected via the state's wide area network.
In summary, the development of a regional ITS architecture and a telecommunications ITS architecture is a critical part of a needs assessment, as these architectures provide the foundation for determining the telecommunications capacity and access points required in the eventual network. With a regional ITS architecture and a telecommunications architecture, agencies minimize the risk that:
- The network may be sized too small to meet the eventual demands
- The network configuration may not match the user’s needs
- An approach is adopted that results in significant additional cost to be expanded to meet the full set of requirements.
A regional ITS architecture and a telecommunications ITS architecture assist agencies in determining the most appropriate telecommunications solution for their ITS deployment.
**NOTE: Since this document was prepared, the following new federal regulations apply: ITS projects funded by Highway Trust Fund (HTF) and the Mass Transit Account (MTA) must have (or participate in) an ITS regional architecture in place by April 8, 2005 for regions now implementing/operating ITS projects (or w/in 4 yrs of 1st ITS project).
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