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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: Date: March/April 2001|
Issue No: Vol. 64 No. 5
Date: March/April 2001
A number of recent developments have coalesced to change conventional wisdom regarding transportation-related communications technology. The Telecommunications Act of 1996, the explosive growth of the Internet, the remarkable technical advances in wireless communications, and a healthy economy for several years are all a part of this change.
These new communications developments bring opportunities and benefits to transportation engineers even though these technologies were not designed specifically for transportation uses. This article explores some new transportation applications and some near-future developments.
Identify Transportation Information Needs
To take advantage of telecommunications opportunities that already exist or will exist in the near future, it is necessary to look first at why telecommunications technology is needed and then to carefully evaluate alternatives for meeting those needs.
The transportation planning process provides the basis for this analysis by defining problems that need to be solved and identifying possible solutions. Some of these solutions will undoubtedly involve the use of electronics to enhance the operation of the transportation network. Upgrading traffic signals, adding video surveillance of freeways or intersections, constructing or expanding a traffic management center (TMC), and installing other intelligent transportation systems (ITS) equipment all require telecommunications technology.
It is essential to understand the telecommunications implications of each project proposed in the transportation plan. This requires analysis of both geographic and information requirements. Where should the output from video cameras go - to the TMC, maintenance shops, or emergency services providers? Is full-motion needed, or would stop-action, single frames suffice? This type of question must be asked for every piece of information to be exchanged among people, systems, and agencies.
This analysis could feed into the "regional architecture" for transportation information exchange. In turn, the regional architecture, to be prepared by every state and metropolitan region over the next couple of years, provides the basis for defining the detailed requirements for telecommunications services needed to implement the transportation plan.
Once the information needs are defined in the regional architecture or other documents, a communications technology specialist can determine the corresponding specifications for telecommunications. Telecommunications systems can be configured several different ways, and the specific attributes of different configurations will be important. Options will depend in part on the communications services provided in the area.
Both the technology and the number of telecommunications vendors have been in rapid flux nearly everywhere. The Telecommunications Act of 1996 fostered an explosion of high-quality telecommunications suppliers in most major urban areas across the country. As a result, we are no longer dependent on monopolistic providers. There are multiple suppliers of wireline and wireless services. As a result, the cost of services has been reduced, and the kinds of services offered has been expanded.
Over the past five years, even experts have continually both underestimated the extent of communications services that will exist in a given area and overestimated the cost of those services. However, it is exactly this rapid change that has created the opportunity to get more for your telecommunications dollars.
Evaluate New Alternatives
There are three broad areas where transportation engineers can capitalize on new telecommunications developments: (1) new infrastructure from new competitors, (2) new technologies for wireline networks, and (3) new services from the wireless industry.
Most transportation engineers are well aware of the tremendous expansion in telecommunications infrastructure over the past few years. They have seen their streets and major roadways dug up to install cables and electronics. This new infrastructure, however, also presents an opportunity to transportation agencies planning new or expanded telecommunications.
The opportunity arises from the competition among multiple communications companies, including traditional telephone companies that are branching into other areas of communications. Consider the myriad of services offered the consumer: Internet access, cable television, satellite television, long-distance telephone, digital telephone, etc.
New competitors typically need large customers, such as government agencies, to provide a solid base for offering their services to customers. Two obvious consequences of this new competition are the reduction in the cost of services and the creation of incentives to improve the quality of service.
Regardless of the telecommunications architecture chosen by a transportation agency, there generally will need to be some form of "backbone" or "wide area network" technology that can collect - and subsequently disseminate - information from widely dispersed field equipment, such as signal controllers, cameras, other sensors, etc.
Increased competition in the telecommunications industry allows transportation agencies to lease rather than purchase communications infrastructure. Owning the telecommunications infrastructure has been standard practice in the transportation community. However, in the few serious evaluations of leasing, the life cycle cost of leasing was half that of owning infrastructure. The cost savings from leasing could be tens of millions of dollars for a statewide or metropolitan network.
Leasing obviously brings its own set of problems; it is no panacea. There are pros and cons. The rapid pace of technological change and the competitive market compel communications companies to keep their networks up-to-date and competitive. By leasing, a transportation agency can keep up with the technology without the heavy burden of new purchases or the unavailability of parts for maintenance.
The rapid change in technology has also reduced the cost of services. In most instances, agencies have overestimated the cost of leased services over time. This dramatically contrasts with a few years ago, when agencies suffered from escalating prices for leased lines from monopolistic providers.
The most difficult task in the evaluation of alternative telecommunications strategies is not the comparison of leased versus owned infrastructure, but rather determining the communications requirements.
|Figure 1 - Digital subscriber line (DSL) technologies provide the ability to use existing twisted pair infrastructure to link equipment in the field (such as the traffic signal controller) to a traffic management center or an intermediate communications hub.|
Using Existing Telephone Lines
Regardless of which wide area network technology is chosen, there are also new alternatives for connecting field equipment to the network. Many agencies are installing, or plan to install, video cameras on their roadways for a variety of purposes. Until recently, this meant installing fiber-optic cable to each of those locations - a costly prospect at best.
Today, however, the telecommunications industry has a new technology that can drastically reduce these costs. Developed for providing high-speed Internet access, the technology is called Digital Subscriber Lines (DSL). It allows very-high-speed data, such as video, to be transmitted over existing copper telephone lines. The technology was designed to provide a high-speed link from a central office or other hub to the consumer's office or home.
Agencies owning standard telephone lines for operating traffic signals can use those lines for transmitting video and signal controls. Instead of installing fiber-optic cable from a TMC or as a backbone port to the roadside equipment, a DSL unit is installed at each end of the telephone line, as illustrated in figure 1.
There are applications of this technology for almost any communications architecture in existence today. Figure 2 illustrates the use of DSL to transmit video from a roadside to a TMC for three different network architectures that might be employed.
DSL technologies have been used in several locations with excellent results, and costs have been a fraction of those associated with installing fiber-optic cables. Furthermore, the installation of DSL equipment can be accomplished in a very short time - days instead of months.
There is no doubt that DSL offers the possibility of greatly expanding data collection from field devices without the substantial capital expense of installing fiber-optic cable throughout a region. (For more information, see "DSL for ITS" at www.its.dot.gov.)
A centralized architecture is often utilized in urban and densely populated suburban environments. In such instances, xDSL solutions provide direct access between the romote camera locations and the TMC.
Distributed Architecture: High-speed backbone
One form of distributed architecture utilizes a high-speed backbone. Frequently used along major freeways, architectures allow for xDSL tail circuits. For example, sDSL can provide the link between a camera along an arterial roadway and a communications hub along the backbone. This arterial location may be several miles away.
Distributed Architecture: Closed Loop (Dial-up)
The Wireless Revolution
Several years ago, the Federal Communications Commission (FCC) authorized the use of new segments of the radio frequency spectrum for a variety of services. Two regions of the spectrum are of particular importance: the 2,400-megahertz and the 5,000-megahertz unlicensed bands. The technical details are less important than the equipment and services now available in these bands.
Four aspects of this development are important for transportation agencies:
1. These bands can support wideband operation - i.e., high-speed data transmission.
2. The associated technologies are portable and can establish communications without being constrained by physical infrastructure, such as cables.
3. Broadband wireless equipment and the applications they support have proliferated, subsequently reducing deployment costs.
4. These bands are approved for license-free operation (no FCC license required). This significantly reduces recurring costs.
The new broadband wireless technologies can support point-to-point and point-to-multipoint architectures. An example of the former is center-to-center communications, and an example of the latter is communications between multiple field devices and a hub - e.g., a TMC. Some of these technologies are capable of supporting multiple video signals, telephone service, Internet access, local area networks, and other data exchanges over a single link.
While transportation agencies can own the equipment needed to support these services, such services can also be leased.
(For more information, see "Broadband Wireless, Integrated Services and Their Application to ITS" under Telecommunications at www.its.dot.gov.)
In addition to the many technologies for providing raw connectivity, new devices can be used to integrate voice, data, and video services. These are called multi-service access devices (MSAD) or integrated service devices. Figure 3 shows the variety of information sources that can be accommodated by MSAD for a wireless link. This equipment makes a telecommunications facility much more flexible by supporting a variety of services. It also makes the provision of many services much simpler and cheaper.
A test is underway to demonstrate the function and utility of these new broadband wireless and integrated technologies. This test will allow the exchange of information between a state TMC and a toll road headquarters 6.5 kilometers (4 miles) away. The wireless link simultaneously transmits live video from surveillance cameras, transmits traffic flow data, accommodates voice dispatch services, and allows video teleconferencing. This link will cost about $30,000 for hardware and installation. There is no requirement for an FCC license, and there are no recurring monthly costs.
This installation will provide more than 15 times the capacity of a T-1 line. Leasing equivalent capacity from the local telephone company would cost about $35,000 per year. Even as a temporary solution, these new technologies can be very cost-effective.
|Figure 3 - Multi-service access devices (MSAD) have a variety of subscriber interfaces to accommodate many different traffic types.|
Just a few years ago, conventional wisdom regarding transportation-related telecommunications was "own your own infrastructure and if you need to install video cameras, trench and bury fiber-optic cable." That advice is no longer wise.
New options are available for virtually every transportation-related telecommunications application. However, to get the most for your telecommunications dollars, you must carefully evaluate these alternatives. First, take the time to understand and define all of your telecommunications requirements. Second, hire a competent telecommunications expert who knows the services available in your area and is capable of evaluating these various alternatives for your application. The result will be an entirely new set of implementation options and a significantly cheaper telecommunications network.
William S. Jones is the technical director of the Intelligent Transportation Systems (ITS) Joint Program Office (JPO) of the U.S. Department of Transportation (DOT). He has been with DOT since June 1995. Currently, he oversees all technical activities in JPO. Prior to joining DOT, he spent 34 years with Westinghouse Electric Corp. in the defense and commercial electronics business. Jones retired from Westinghouse in 1994 as the vice president and general manager of the Transportation Management Systems Division, which he started in 1990 as an application of Westinghouse's defense technology to the transportation industry. He spent most of his career in the development of new sensor technology in radar, infrared, and optical systems, as well as the application of real-time computing for electronic systems. Jones has a master's degree in electrical engineering from Washington University in St Louis, Mo., and a master's degree in business administration from George Washington University in Washington, D.C. He is a registered professional engineer in the state of Maryland.