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Trend Watch: Broadband Spread Spectrum
"Spread spectrum is a mode of radio communications commonly used in ITS. It is a form of wireless communications in which the frequency of the transmitted radio signal is deliberately varied or spread across a bandwidth. This greater bandwidth means that there is no interruption or interference as compared to using a specific radio frequency. With the use of spread spectrum, data collection, as well as command and control directives, are sent between signalized intersections, dynamic message signs, vehicle detectors, cameras, transportation operation centers, and motorist information systems.
An advantage of using spread spectrum is the cost. Many ITS components, such as traffic signals, detectors, and dynamic message signs are spread out along roadways and entire metropolitan areas. Physically interconnecting all of these components may involve many miles of conduit and would likely be the most expensive item of the ITS project. Spread spectrum requires a transmitter and a receiver; the cost is a mere fraction of physical interconnection and set-up time can take as little as an hour. The availability and cost of spread spectrum is such that even small municipalities and counties can now take advantage of this technology. In the case of traffic signal interconnection, spread spectrum can be as little as one-tenth the cost of the conventional physical interconnection via metal conduits. While spread spectrum may not be an exclusive mode of communication in ITS projects, it serves a vital role in providing versatility and cost effectiveness.”
Ted M. Andrews, PE
Senior Project Manager
CTE |
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It's not enough to just build good, solid roadways that get drivers to and from their destinations. Today's “superhighway” planners and designers are incorporating Intelligent Transportation System (ITS) elements to help monitor and manage traffic flow, reduce congestion, and, ultimately, save lives. ITS encompasses an array of wireless and communications-based information and technologies that are integrated into the transportation infrastructure. Always at the forefront of traffic engineering technology, CTE is implementing ITS on projects throughout the country.
CTE and sister company DMJM Harris are part of AECOM's Americas Transportation Group. The combined expertise of the transportation group offers our clients the best talent in the field and the ability to share valuable resources. Our collective experience has taught us to focus on key areas to best serve our clients: simplicity of design, maintainability, cost-effectiveness, constructability, funding, and software and systems integration.
The Dan Ryan Expressway reconstruction in Chicago included a complete overhaul and expansion of the existing surveillance, ITS elements and communication infrastructure. CTE and its subconsultant were responsible for the complete design of an integrated system for the 10-mile corridor that included closed-circuit television (CCTV), dynamic message signs, highway advisory radio (HAR), ramp metering, and an upgrade of the Illinois Department of Transportation's (IDOT) District One communication system. This $20 million system also includes over 50 miles of distribution and backbone fiber optic cable.
CTE designed the dynamic message signs, highway advisory radio, and a portion of the CCTV systems. Older dynamic message signs were removed and replaced with 13 new, full matrix, walk-in type LED signs. These new signs convey travel times, traffic warnings, Amber alerts, and other important information to the traveling public. The walk-in design of the signs allows for maintenance to be performed from inside, eliminating the need for lane closures. Meanwhile, the CCTV system installed on the Dan Ryan project is IDOT's first major installation of cameras on high mast towers. Images from these cameras are sent over fiber optic cables to IDOT headquarters where they are used to monitor road conditions and relay information to rescue workers at accident scenes.
CTE has also been selected by Tennessee's Department of Transportation to provide construction engineering and inspection services for nearly 20 miles of ITS equipment installations in the Nashville area. This project is a joint effort, combining the talents of both CTE's Nashville and Chicago offices. And, two upcoming projects in Wisconsin will involve ITS and traffic engineering – State Trunk Highway 21 from Omro to Oshkosh, and State Trunk Highway 50 from Lake Delton to Lake Geneva. Traffic engineering will be vital, with corridor studies and traffic projections and analysis planned for both projects.
DMJM Harris is busy in Ohio, providing freeway management design services for the Department of Transportation projects in Cleveland, and Akron and Canton. The Cleveland project covers an area of over 300 miles and includes the following sub-systems: 28 dynamic message signs, 81 CCTV cameras, 47 non-invasive / non-intrusive detectors, two highway advisory radios, and 125 miles of fiber-optic communications supported by wireless communications in certain areas. The approximate 125-mile coverage area for the Akron and Canton project includes all the major interstates, Urban Principal Arterials and other freeways and expressways. The design of the system focuses on Gigabit-Ethernet communications topology, carried over a hybrid media that includes dedicated fiber optic, wireless, and leased telecommunications services. This infrastructure will transport data from CCTV, dynamic message signs, speed and volume detection (non-intrusive), incident detection via interface with local public safety dispatch centers, and HAR, and will operate from a control center, with distributed capabilities for operating the system from one or more remote locations.
CTE has been involved in the development of ITS systems in the Chicagoland area for more than 20 years – from the installation of some of the first “changeable message signs” on the Kennedy, Eisenhower, Kingery and Dan Ryan Expressways in the late 1980's for the first Dan Ryan reconstruction projects to our ongoing relationship with the Illinois Tollway Authority.
So what's on the next horizon for traffic engineering and Intelligent Transportation Systems? Broadband spread spectrum (see box left) is quickly emerging as an option that is also affordable for smaller communities with budget constraints, while electronic toll collection is another fast-growing element of ITS. And, tying together the many elements of ITS, in sophisticated traffic operations centers and disseminating the collection of data quickly – to police and fire authorities, for example – is the ultimate goal for those who plan, build and maintain hundreds of thousands of miles of roadways that crisscross our country. |
