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4.4.3.2 Traffic-Related Functional Flow Diagrams

Issues surrounding the control and surveillance of traffic are key components of any ITS regional deployment and depend upon the coordination of multiple entities. The Functional Flow Diagrams presented in this section all revolve around how traffic control and surveillance are and could be provided. Please refer to the narratives associated with each flow diagram for specific explanations of each element.

The Freeway Control functional flow diagram provides a basic representation of the types of communications and roadside equipment needed to control the major aspect of central Ohio's freeway systems; e.g., ramps, lanes and interchanges. Coordination and integration of ramp meters are also included here. This flow diagram is consistent with typical urban traffic freeway control systems. It incorporates the instrumentation included in the Network Surveillance functional flow diagram to support freeway monitoring and includes the capability to use surveillance information to detect incidents on the freeway. Additionally, this flow diagram illustrates how general advisory and traffic control information can be provided to the traveler while en route. In central Ohio this functional flow diagram is linked closely with the Surface Street Control functional flow diagram because the plans for the Columbus Metropolitan Freeway Management System are to be tightly integrated with the city of Columbus' signal system.

Traffic Management's freeway control functions will be performed by the Columbus Metropolitan Freeway Management System. In central Ohio control is achieved by two means: ramp meters and VMS. Ramp meters are currently in operation and controlled by the city of Columbus' TMC, and VMS's will come on line with the Columbus Metropolitan Freeway Management System. Operators at the Columbus Metropolitan Freeway Management System, working with the city of Columbus' TMC, will have the capability to control the flow of traffic on the freeways by modifying ramp meter parameters. Furthermore, they will be able to potentially divert traffic by providing travelers with incident and congestion information through the VMS. This control will be done in conjunction with the use of the surveillance equipment outlined in the Network Surveillance functional flow diagram. Surveillance equipment includes: loops in the pavement to provide flow and speed data and CCTV cameras to provide images of the freeway itself. This instrumentation will exist not only on the freeways but on selected major arterials as well.

As noted in 1, Traffic Management's control of the Roadway, in this case the freeways, will be conducted by the Columbus Metropolitan Freeway Management System. The ramp meters and VMS will receive control information from the Columbus Metropolitan Freeway Management System and provide back system status information. Additionally, the surveillance equipment installed on the freeway, loops and CCTV cameras will provide traffic flow information and traffic images as well as status of the equipment itself.

This functional flow diagram provides a basic representation of how information on travel conditions is collected and distributed. Network Surveillance represents a summary or macro level presentation of surveillance on both central Ohio's freeways and surface streets. Both of these are broken out in greater detail, to include both surveillance and control, with their own functional flow diagrams: Surface Street Control and Freeway Control.

Traffic Management's Network Surveillance functions will be performed by the Columbus Metropolitan Freeway Management System, other TMCs in the region (i.e., city of Columbus TMC, city of Dublin TMC) or a Regional Transportation Management Center. These elements should work in an atmosphere of cooperation and integration to the greatest extent possible. Some level of integration is already planned. For example, the Columbus Metropolitan Freeway Management System will be integrated with the city of Columbus' signal system as part of Phase 2 of the city's Y2K mitigation program. Furthermore, the cities of Dublin and Gahanna have shown interest in receiving the surveillance feed from the Columbus Metropolitan Freeway Management System. This feed would allow the city of Dublin's TMC the ability to access all the information being gathered from the Region's Freeway Management System to include: images from the CCTV cameras along the freeways and major arterials, messages being displayed on the VMS and the traffic flow map. They will also have the capability to control the CCTV cameras near their jurisdiction. This capability could be preempted by the region's Freeway Management System Control Center in case of an emergency. Other traffic management centers (e.g., city of Gahanna) have indicated interest in receiving this feed and have their own similar Network Surveillance capability.

As noted in 1, Traffic Management centers around central Ohio will be gathering a great deal of Network Surveillance information. However, in order to decrease congestion and improve travel in general to the greatest degree, this information must be provided to the traveler. For this flow diagram the Traffic Management centers will interact with the Information Service Provider by receiving traveler information from sources such as local television stations. For example, Channel 4 in Columbus currently provides information to the city of Columbus' Traffic Management Center. This relationship, to include type/level of information and potential Information Service Providers, is explained in greater detail in the Traveler Traffic Information, Broadcast Traveler Information and Interactive Traveler Information functional flow diagrams.

As noted in 1, surveillance information at the Roadway will be provided to Traffic Management centers and then disseminated to Information Service Providers and ultimately to the traveler. The information provided will be gathered through a variety of means. These include loops in the pavement to provide flow and speed data and CCTV cameras to provide images of the network itself. This instrumentation will exist on freeways and major state routes as part of the deployment of the Columbus Metropolitan Freeway Management System, but is available today on surface street systems that include the city of Columbus' signal system; e.g. city of Dublin, city of Hilliard, city of Gahanna, etc. As noted in 1, an ultimate goal of a regional approach toward integrating these systems would be the ability to share the information gathered from a variety of sources and jurisdictions with each other. Although the Columbus Metropolitan Freeway Management System will be central Ohio's major data resource, the sharing of multiple jurisdiction traffic information will provide traffic management center operators with the ability to solve traffic problems in their jurisdictions more efficiently. For example, by having more eyes on the entire system, operators could anticipate problems due to an incident outside their jurisdiction and react to the additional traffic being generated now diverting onto their system in a more timely manner. Furthermore, ODOT's road weather system provides information on ice/snow/rain conditions to various TMCs around the state. This represents another type of information capable of being integrated.

Network Surveillance will also be gathered via COTA's and OSU's Transit Management centers' network of coaches operating on the surface streets around the county. COTA is in the initial stages of implementing AVL which will provide Traffic Management centers with an additional surveillance resource as the coaches act as probes on the region's surface streets. OSU currently has an AVL system installed on its coach fleet. This is explained in much greater detail in the Transit Vehicle Tracking functional flow diagram.

Safety Management centers also play a key role in providing surveillance information to Traffic Management centers. The City of Columbus Division of Police has discussed gaining the ability to receive Network Surveillance information from the region's Freeway Management System at a mobile Incident Command Center. This mobile center could then, in turn, provide audio and video updates on incidents the police are working on. The City of Columbus Division of Police's helicopter could also provide live video updates to Traffic Management during incidents on the Roadway.

Police and fire divisions currently provide Traffic Management centers with updates on incident information indirectly. Both organizations operate with an 800MHz-radio system. Traffic Management centers can then monitor the radio traffic to receive incident updates. This link is not as dependable as it could be, and represents an opportunity for improved integration among organizations.

This functional flow diagram provides capabilities for analyzing, controlling, optimizing and integrating Regional Transportation Management. These capabilities provide for regional optimization and integrated control of network signal systems with freeway control and coordination of area transit and emergency service providers. These capabilities could be provided by a Regional Transportation Management Center (RTMC) that integrates the operations and communications of all salient transportation stakeholders, including traffic, transit, safety, and planning.

Regional Transportation Management can be achieved through a centrally located RTMC or through a virtual management center involving linked, distributed workstations. The RTMC could be able to communicate with other TMCs in order to receive and transmit traffic information on other jurisdictions within the region.

The RTMC could also support any other demand management policies that can alleviate congestion and influence mode selection. It may also communicate with other transportation management centers to coordinate traffic information and control strategies in neighboring jurisdictions.

A central Ohio RTMC could include the following stakeholders: Columbus Metropolitan Freeway Management System, city traffic signal systems, Franklin County Emergency Management Agency, COTA communication facility and the City of Columbus' EOC.

The Surface Street Control functional flow diagram provides a basic representation of the central control and monitoring equipment, communication links, and the signal control equipment that support local surface street control and/or arterial traffic management. A range of traffic signal control systems is represented in this diagram, ranging from static pre-timed control systems to full traffic responsive systems that dynamically adjust control plans and strategies based on current traffic conditions and priority requests. Additionally, general advisory and traffic control information can be provided to the driver while en-route. This diagram is generally an intra-jurisdictional package and does not rely on real-time communications between separate control systems to achieve area-wide traffic signal coordination. Systems that achieve coordination across jurisdictions by using a common time base, or other strategies that do not require real-time coordination, could also be represented by this diagram. Its should be noted that this type of coordination is currently being done between the city of Columbus and some suburban cities such as Bexley and Whitehall. However, for this coordination to take place, the city of Columbus must operate its signals from its TMC. There is an interest to provide this type of coordination without the suburban city having to relinquish control. This functional flow diagram is consistent with typical urban traffic signal control systems. It incorporates the instrumentation included in the Network Surveillance functional flow diagram to support freeway monitoring. In central Ohio this market package is linked closely with the Freeway Control functional flow diagram due to the plans for the Columbus Metropolitan Freeway Management System being tightly integrated with the city of Columbus' traffic signal system and TMCs.

Traffic Management in this diagram includes the Columbus Metropolitan Freeway Management System, other traffic management centers in the region (i.e., city of Columbus TMC, city of Dublin TMC) or a Regional Transportation Management Center. Surface Street Control; i.e., the capability to control traffic signals at major intersections and on main highways for urban areas in central Ohio, is achieved by a variety of types of signal systems including timed and closed loop. Traffic Management center operators will be able to modify signal systems in response to incidents, special events and other unplanned high levels of congestion. Some of the local TMCs (city of Columbus, city of Gahanna) augment their Surface Street Control by surveillance provided by loops and CCTV cameras located around the city. City TMCs also utilize pavement loop detectors for surveillance of the surface street system.

As noted in 1, Traffic Management's control of the Roadway, or in this case surface streets, is conducted through the use of open and closed loop signal systems. These systems are controlled by Traffic Management centers and provide equipment status information. Furthermore, surveillance information is provided by pavement loop detectors and CCTV cameras, as well as status of the equipment itself. It is important to note that due to Ohio's home rule environment this functional flow diagram is currently generally constrained to a single jurisdiction.

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