Freeway Management and Operations Handbook
Chapter 14 – Transportation
|Ramp Management and Control (Chapter 7)||The data collected from detection and surveillance components in the field is synthesized at the TMC, and systems and operators in the TMC monitor and manage the ramp management systems. Central software within the TMC often communicates with and controls the operation of the ramp controllers in the field.|
|Lane Management and Control (Chapter 8)||The data collected from detection and surveillance components in the field is synthesized at the TMC, and systems and operators in the TMC monitor and manage the lane management systems.|
|HOV Systems (Chapter 9)||For HOV systems using automated gates, overhead lane control signals or dynamic message signs (DMS), these central systems are typically located and maintained at the TMC and the monitored and managed by TMC software and operators.|
|Traffic Incident Management (Chapter 10)||The TMC is the nerve center for transportation agency management of traffic incidents. In some multi-agency centers that include emergency management dispatch, the TMC can act as the situation or war room for multi-agency response and coordination.|
|Planned Special Event Management and Control (Chapter 11)||The TMC is the nerve center for the transportation agency management of planned special events. In some multi-agency centers that include emergency management dispatch, the TMC can act as the situation or war room for multi-agency response and coordination.|
|Emergency & Evacuation Management (Chapter 12)||The TMC is the nerve center for the transportation agency management of emergency and evacuation events. In some multi-agency centers that include emergency management dispatch, the TMC can act as the situation or war room for multi-agency response and coordination.|
|Information Dissemination (Chapter 13)||Information dissemination is one of the primary roles of a TMC. The TMC is the gathering place for real time information and planned special event information, and it is from the TMC that the information, created from fused and synthesized data, is distributed to stakeholders via roadside infrastructure (DMS and Highway Advisory Radio). TMCs also distribute traveler information to independent service providers and the media for distribution to the public. In some systems, TMCs also provide traveler information directly to the web or telephone information systems (511).|
|Detection and Surveillance (Chapter 15)||The real time data (e.g., volume, speed and occupancy, location, etc.) from detection and surveillance infrastructure is collected, fused and synthesized at the TMC for use by agency management systems, performance monitoring, control systems, and in determining travel conditions.|
Reference 1 defines a Transportation Management Center as "a central facility that controls, monitors, and manages the surface street, highway, transit and bridge/tunnel control systems within its control area. To accomplish these tasks, a TMC aims to manage the operation of the transportation system by communicating travel condition information, making necessary modifications to traffic and transit control systems, and directing response activities. TMCs are a component of transportation management systems, a primary means that transportation agencies can use to manage traffic flow and make better use of the existing transportation system. Within the system, then, TMCs work with other elements (components) to accomplish the goals and objectives of transportation management. These components include field hardware (cameras, variable message signs, electronic toll tag readers, etc.), communications equipment, and the policies and procedures established to deal with various transportation-related events that impact the system. TMCs play a critical role in managing travel on the surface transportation system and support the many interests who provide a variety of services to the traveling public. TMCs can serve as the technical and institutional hub for bringing these interests together within a metropolitan area, entire state, or region."
TMCs can be either stand-alone facilities or, as is becoming much more the rule rather than the exception, networked with other TMCs to provide regional management (Note: Networked TMCs (center-to-center linkages) are discussed in Chapter 16). They can be owned or operated by a single agency, multiple transportation agencies, or multiple agencies with different charges like transportation, emergency service, or media agencies. They operate different days of the week and different times of the day, from weekdays only and only during peak periods to 24 hours a day seven days a week.
Often, when one thinks of a TMC they imagine a building or a room – a control room, two-way radios and police scanners blaring, multiple computer monitors at each work center, closed-circuit television monitors on the wall, people scurrying around – a beehive of activity (e.g., "Houston, Tranquility Base here, the service patrol has arrived"). Surely this is a TMC, but not every TMC. A Traffic Management Center is just that – a center or hub for gathering and sharing information, making operational and management decisions, and implementing control strategies to affect these decisions. Whether it is an exclusive building, a floor of a building, or a room in a maintenance shed, it is a place where multiple functions or activities are performed in coordination and perhaps with other stakeholders. It is the focal point that, without it, freeway management in large or complex networks could not be effectively performed.
A TMC doesn't even need to be a physical structure. In this "Virtual TMC" scenario, there is no centralized location where operations occur; but instead, everyone is "attached" to the system remotely. In effect, the system is decentralized. This virtual concept is based upon the premise that much of the effort in traffic management is one of communicating between agencies, and this can be done without the use of expensive TMCs. As noted in Reference 3: "Significant benefits can be realized through decentralized advanced traffic management system (ATMS) designs that enhance the ability for communication among participants in the transportation management process. This approach is compatible with current trends in ITS which eliminate single-agency single-function systems in favor of a more comprehensive approach that includes all participants in the traffic management process. Perhaps the most exciting result of the decentralized design is that it permits the development of a virtual system that provides improved traffic management capabilities while lowering the cost and disruption caused by a centralized system. This is accomplished by eliminating the need for an expensive control center and the requirement for changes in operational procedures and relocation of personnel."
The basic activities that define the purpose of a TMC are summarized below (from Reference 4):
In essence, the TMC serves many purposes: as a real-time command and control center, a communications center receiving and disseminating information, a center where the appropriate response vehicles or equipment is dispatched in response to an incident or other event, a coordination center where multiple agencies gather to coordinate activities for large incidents or planned special events, a training center where operators or stakeholders are trained in the concepts of real-time freeway management, an interface with the media, a storage facility where data collected from field systems are archived for use at a later time for a number of purposes, some not related to traffic management .
TMCs afford numerous benefits, although studies to date have not separated the benefits of a transportation management system itself from the benefits of housing the system in a center. An NCHRP Synthesis Report on "Transportation Management Center Functions" (Reference 5) identifies the following in its conclusions:
Other potential benefits specific to systems with a dedicated center are listed below:
The TMC for a freeway management system is such an integral part of a large or complex freeway management and operations program, that the TMC – its functionality, location, layout, staffing, operations, etc. – must be a key consideration in every aspect of developing the freeway management program (e.g., stakeholders, goals and objective, needs, concept of operations, requirements, etc., as shown in the funnel diagram in Figure 3-1). The vision, goals, objectives, operational concepts, and requirements for the overall freeway management program will impact decisions regarding the TMC; just as the TMC designs and operating procedures will impact the freeway management program. Moreover, given the complex technologies associated with a TMC (computers and processors, real-time software applications, communications networks), the development and implementation of the TMC (and associated ITS projects) should utilize a "systems engineering" process and incorporate "configuration management". These processes are summarized in Chapter 3, and addressed in greater detail in Section 14.3.
The TMC represents the physical representation of one or more of the 10 "center subsystems" identified in the National ITS Architecture (e.g., traffic management, emergency management, toll administration, commercial vehicle administration, maintenance and construction management, information service provider, emissions management, transit management, fleet and freight management, archived data management), as well as the location of many of the "terminators" (e.g., operators, managers). Further, the TMC "houses" collected data, thereby performing the functions of an "ITS Data Mart" and "ITS Data Warehouse", both National ITS Architecture market packages. Moreover, given that a TMC is such an integral part – the focus, if you will – of a freeway management system, its operation also impacts numerous other Market Packages and User Services.
The TMC can consist of several "technical" elements, including:
Many of these TMC elements are discussed in the following sections. Much of the information included herein was extracted from the Human Factors Handbook for Traffic Management Center Design (Reference 6).
The TMC's physical environment consists of design elements that allow the system – both human and machine components – to function effectively. The following lists some physical elements that designers must consider:
The requirements for some of these elements are mandated by public law (e.g., access for the disabled). The design of other features of the TMC should be based on established design practices (e.g., lighting standards for designated work areas). The Human Factors Handbook for Advanced Traffic Management Center Design (Reference 6) provides guidelines and requirements that can be used to design the physical environment of a TMC; and should be consulted for more detailed recommendations and specifications.
The size of TMCs can vary considerably, depending on the design objectives and functions performed by the system. Factors that affect the design of the center include the following:
The size of traffic TMCs varies widely throughout the United States. Some TMCs, such as TransGuide in San Antonio, Texas, and Transtar in Houston, Texas, occupy as much as 4,800 m2 (52,000 ft2); however, many successful TMCs occupy less space. For example, the TMC in Minneapolis, Minnesota occupies only approximately 950 m2 (10,000 ft2).
A typical TMC has the following work areas within the building:
Examples of typical floor plans for a TMC are shown in Figures 14-2 and 14-3.
The operations room is the hub of the TMC. It houses the operators' workstations and display boards/video terminals used to display information about conditions in the network to the operators. The size of the operations room is dictated by the number of operator workstations that will ultimately be in the TMC, and the type and location of the information displays.
The computer/peripheral area houses the computers needed to run the freeway operations center. The size of the computer room depends upon system design decisions regarding how much computer capability will be based at the TMC as compared with that installed at hub locations in the field. Often these rooms require strict environmental controls (i.e., heating and air-conditioning). Many locations also have strict access control for this area.
The communications area can be a stand-alone area or can be combined with the computer/peripheral area. The communications area is the terminus for data entering and exiting the TMC from the field. It also serves as the distribution point for transmitting data to the rest of the system (i.e., the computer and video control systems).
Many locations like to provide a gallery or viewing area of the operations room. From this area, tours of the TMC can be conducted without interrupting the operations in the TMC. This area can also be used as a training center where trainees can monitor the operators without disturbing them.
Many TMCs also have an area set aside for the media. Some TMCs use the gallery area to service this function, but others have set aside a separate area as a media area. From this area, the media can watch what is going on in the operations center without interrupting the operations. Often, these areas have several telephones and video terminals that are available for use by the media during incidents or emergencies.
Besides these common areas, office space should be provided to those working in the TMC. The number of office spaces, again, depends upon what functions will be carried out in the TMC. Generally, office space is required for the operations supervisors, the system support staff, the maintenance supervisors, and the engineering and administrative staffs.
Some agencies have included space for their system maintenance personnel at their TMCs. If maintenance operations will be based at the TMC as well, the space provided at the TMC is based on the number of electrical maintenance personnel that will be stationed there. In addition, if the TMC is also expected to serve as an Emergency Operation Center (EOC), then additional space is needed for such items as dormitories, a large kitchen, and showers. Some locales may have mandated structural requirements for an EOC that are more stringent than for regular commercial office space. Finally, some centers house their emergency dispatch vehicles and equipment, and as such, include garage facilities.
Other notable design features related to the physical plant of the TMC are listed below:
Lighting is an important consideration in the design of a TMC. Viewing a large situation map with LED signals or a bank of CCTV monitors, for example, is not compatible with high levels of general illumination. On the other hand, many operators' tasks cannot be performed in low levels of illumination. The lighting scheme and choice of luminaries must be viewed as an integrated whole, and not designed piecemeal (6).
The greatest challenge in designing the lighting in the TMC revolves around the need to provide dim general illumination and higher levels of local illumination. Usually, a low level of illumination is provided in the operations room because of the nature of the tasks and displays used. Most centers provide supplemental lighting at each operator console. Some general recommendations related to lighting in TMCs are as follows (6):
Communications between operators can be critical, especially in emergencies. Common sources of noise in a TMC include alarms, radio/telephone communications, operator conversations, and data processing equipment. Overall, the noise level in a TMC should not so high as to interfere with normal speech between operators. The objective in designing for noise is to balance the different sound sources so that local speech is unaffected, but is sufficient to mask intrusive noise from adjacent spaces. Some general recommendations for reducing the impact of noise in the TMC include the following:
Operator comfort and performance can be affected by temperature and air quality. In designing a TMC, designers must be concerned about two issues related to the thermal environment of the TMC – the general heating, ventilating, and air conditioning (HVAC) standards for occupied buildings, and the effects of local thermal conditions related to special equipment such as computers and video display units. Sometimes, special rooms in the TMC, such as the computer/peripheral room or the communications area, may require separate heating and cooling standards. The Human Factors Handbook for Advanced Traffic Management Center Design (Reference 6) summarizes the heating and cooling standards applicable to TMCs. General standards that should be considered in the design of the heating and cooling system for TMCs include the following (6):
Integral to any TMC are the means by which operators enter and retrieve information. Controls allow the operators to guide certain traffic parameters (e.g., traffic flow) within the limits of the center's mission. Displays provide information that operators need to monitor the status of the system and make control decisions. The operator workstation is often the primary means by which operators interact with the system. Examples of operator workstations are shown in Figure 14-4.
Workstation design is dependent on several issues – the layout and space availability within the TMC, the functions of the freeway management system and how those functions are allocated within the FMS software (including the level of automation), and the software itself. For example, if the decision is made that each workstation will have access to all functions in the center and there are multiple types of systems included – not all of which are able to be operated from the same platform, or some requiring larger displays or different types of interfaces – the design of the workstation will be very different than if all of the functions can be incorporated into the same software package or can be operated on the same platform. Similarly, if the control room is too small to hold separate workstations, customized fixtures designed specifically for the TMC under development may be required.
The layout of workstations and other furniture and fixtures should be specified as part of the overall work space design. In designing workstations, comfort and suitability should be considered as important issues, both of which are supported with many experience-based guidelines (Note: The Human Factors Handbook for Traffic Management Center Design (Reference 6) summarizes many of these guidelines).
Well-designed workstations and supplemental furnishings (e.g., chairs) can prevent discomfort and perhaps occupational injuries (e.g., back strain, cervical stress disorder, carpal tunnel syndrome, and repetitive stress disorders). A good design will contribute to productivity and employee health and morale, while a poor design can actually limit productivity. Designing the workplace to accommodate the characteristics and capabilities of human operators is often referred to as ergonomics. The strong movement toward ergonomic suitability has created many sources of information that support proper workstation design; however, an experienced ergonomist or human factors engineer should be consulted before a large investment is made in workstations. If possible, consultation with the TMC Operators should be employed in the design of the work centers.
Considerable changes in workstation design have occurred as freeway management systems have evolved over the last three decades. In the past, most TMCs were designed with multiple workstations, each with a specific function. For example, one workstation controlled the video surveillance system, another controlled the variable message signs, another controlled the ramp metering system, etc. This type of design required the operators to move between a series of workstations to implement a control strategy in a specific situation. Today, most control consoles are being designed so that a single operator can operate all of the subsystems from a single workstation. This generally results in better operational control over the system; however, in some situations, two or more operators may be competing for control of the same camera or monitor. Methods of setting priorities whereby multiple functions can be performed at a single workstation need to be established.
The design of individual workstations in a TMC varies depending upon the functions to be performed by the operators. All workstations should be designed to ergonomic standards. The placement of video display monitors and input devices (e.g., keyboards, mouse, trackballs, switches, etc.) should also conform to recognized standards and guidelines. Common ergonomic design problems include the following:
Glare is one of the most common problems with video display units incorporated into workstations. Glare is generally caused by either lighting sources at the workstation or at other nearby video display units. Glare problems can be eliminated by several means, including providing glare shields between video display units and light sources; covering light sources, including windows; and using task lighting.
The user interface is a software element of the system that connects the operator with machine functions in an easy-to-understand format. If the smooth execution of system functions is desired, interfaces between operators and computers must be designed properly. TMC controls and displays should be designed according to the type and quantity of information that the operators must process, and the capacities and demands of the operators who will use the information they provide.
Many troublesome human factors problems are the result of poor user interface design. Poorly designed controls and displays can affect the operations of the TMC and the operators themselves. Inadequate controls and displays can cause cognitive information processing deficiencies, faulty situation assessments and decisions, inaccurate data and command entry, occupational stress, and a general loss of operating efficiency.
The steps involved in designing acceptable user interfaces include the following:
Examples of user interface screens are provided in Figure 14-5.