Traffic Management > Traffic Management Centers

• Introduction
• System Description 
• Types of TMC
• Major Functions
• Assessment 
• Key Results
• Benefits and Costs
• Implementation and operational challenges
• Case Studies
• Houston
• Los Angeles
• Minnesota
• Chicago
• Seattle
• Phoenix
• Detroit
• San Antonio
• Atlanta
• Milwaukee
• References 

INTRODUCTION

The concept of traffic management in the United States arose in the 1960s and 1970s  when traffic volumes rapidly increased and the construction of new highway systems  slowed, forcing agencies to manage the demand on the existing system without  expanding the capacity. The Traffic or Transportation Management Center (TMC) has become the
focal point for operating and monitoring traffic management systems. Transit properties have been managing their fleets from such centers and large traffic signal systems have been under central control for many years. The Illinois Department of  Transportation has been managing freeway incidents from its Chicago TMC for over four decades.

SYSTEM DESCRIPTION

The TMC is a facility through which management and coordination of transportation resources and technology takes place.  It can be considered as the core of a transportation management system, where information about the transportation network (freeway system, traffic signal system, or transit vehicle network) is collected and processed, and fused with other operational and control data to produce information. The information is used by system operators to monitor the operations of the transportation system and to initiate control strategies to effect changes in operation, when recurrent or non-recurrent congestion occurs. It is also the focal point for communicating transportation related information to the media and the motoring public. The TMC links various elements of Intelligent Transportation Systems such as  variable message signs, closed circuit video equipment, roadside count stations, etc., enabling decision makers to identify and react to an incident in a timely manner based on  real-time data. Communication links can range from hardwire links (such as leased or  dedicated telephone lines, fiber-optic or coaxial cable), to links which utilize wireless  technology such as microwave and cellular communications. 

Types of TMC

Each TMC currently operating in the United States is unique varying by size and  functionality. TMCs are implemented as Freeway Management Centers, Traffic Signal System Centers and Transit Management Centers depending on their function.

Freeway Management Centers
A freeway management center is responsible for the monitoring and control of traffic on an interstate highway or comparable limited access roadway. It focuses its efforts on detection, verification, and active management of incidents which reduce roadway capacity; on distribution of information to travelers; and on optimization of roadway capacity through active strategies such as ramp metering.

It receives notice of incidents through a network of sensors (loop detectors, radar, etc.) which continuously monitor traffic flow (speed, occupancy, and/or volume), motorist calls, '911' calls, vehicle “probes” (such as those monitoring flow of vehicles which carry radio frequency transponders or are actively transmitting location derived from on-board global positioning systems), monitoring video images from roadside cameras. Following notification, incidents are typically verified through these same cameras. Incident  responses vary, including notification to law enforcement, emergency services, HAZMAT,  maintenance, motorist assistance patrol, wreckers, and posting of messages to approaching motorists via variable message signs and highway advisory radio.

Traffic Signal System Centers 
The center monitors flow of traffic on the surface street network, and intervenes by  adjusting signal timing whenever necessary. Similar to freeway management centers, traffic signal system centers that have access to resources to identify incidents would take similar actions as described above to identify and address incidents. They may also  interact with the freeway center by altering signal timing to create diversion routes around major freeway incidents. Projects such as DIVERT in Minneapolis demonstrated this capability.

Examples of traffic signal control centers include the RESCU center in Toronto, New York City's signal center, and the ATSAC center in Los Angeles. Another interesting example is the SCATS center in Sydney, Australia, which is responsible for approximately 4000 centrally controlled intersections, and which is staffed and operated by the local police, under regional law. 

Transit Management Centers 
Their task is to track and support fleets of transit buses or railcars. It can be particularly critical in mixed fleets, where coordination of the bus/rail interface is essential to client satisfaction and to cost-effective operation of the transit network. Examples of transit management centers that exist in the U.S. and elsewhere, include the MARTA center in Atlanta, the WMATA center in Washington, D.C., and the BART center in California's bay area. 

Major Functions of TMC

Roadway Management 
Roadway management is the monitoring and control of the flow of recurrent traffic. It consists of active flow balancing between alternate routes, provision of relative travel times for alternate routes and ramp metering . Control of HOV facilities is also included in this category, especially when the HOV lane is reversible, and its operation may include gates or relocating a movable barrier. 

Incident Management
TMC brings together the components, programs, and strategies that comprise incident and congestion  management. Common incident prevention techniques include providing traveler warnings of unsafe or congested roadway conditions, motorist assistance patrols, effective management of lane closures and rapid dispatch of resources to repair road damage or to remove debris. By effective incident response and clearance techniques TMC reduces the number of lanes closed and creates alternate routes. Providing traveler information regarding the incident, in hopes of reducing the number of vehicles delayed by the incident and minimizing the likelihood of secondary incidents, is also given importance. 

Fleet Management
Fleet management includes the monitoring and active management of a group of vehicles operating on the roadway or rail network. The most common component is vehicle location monitoring, either automatically (via automatic vehicle location technology) or manually (by radio contact with the vehicle operator), from which schedule adherence and vehicle headways can be determined. 

Traffic Signal Control
TMC monitors the traffic flow on the signalized roadways and responds to the condition of the traffic signal network. It may adjust signal timing plans (either directly by altering the plan currently in operation or by activating an existing plan), or may change the mode of operation of one or more signals (to flash, actuated operation, or fixed-time operation). The TMC may also dispatch maintenance resources to address signal system problems or may request dispatch of law enforcement to direct traffic if signals at an intersection becomes inoperable. It may also attempt to restart or correct faults in the signal system or with the communication with the signal system. If the signal center has appropriate assets, it may also perform incident management, and may provide traveler information to travelers on the roadways under its jurisdiction. 

System Control and Data
Acquisition System Control and Data Acquisition (SCADA) functions are performed by many TMCs. The best examples of SCADA functions are related to tunnels, and include ventilation, fire detection and suppression, security monitoring, motorist telephone system, etc. In the Arizona TrailMaster TMC, SCADA functions also include control of irrigation in the highway medians. Another type of SCADA function, at the Boston Central Artery/Tunnel Integrated Project Control System, is AM/FM rebroadcast. 

Multi-Agency Coordination
Involving all agencies active in the situations addressed by the TMC ensures that the center is optimally configured, equipped, and staffed to achieve full benefits. Ideally, the concept of operations will reflect the actions and methods of each partner in transportation management, and will reflect the resources and capabilities necessary to achieve the chosen operational method. 

Information Dissemination
The focus of multi-agency coordination is the dissemination of information. Typical examples of infrastructure-based information sharing include messages on variable message signs and highway advisory radio. Non-infrastructure intensive traveler information includes provision of information via broadcast media, press, Internet, telephone systems, or via fax. Information sharing may occur as part of event planning, during an event, or following the event. This includes both planned events (such as parades) and unplanned events (such as traffic incidents). 
Examples include the detailed plans prepared by Houston Metros law enforcement staff at the TranStar control center detailing freeway, arterial, transit, and crowd control plans for major events such as the annual Rodeo. Multi-Agency coordination is of even greater importance for traffic signal systems. Where neighboring centers control signals along a primary signalized corridor, coordination is critical to achieving optimal flow conditions. Interaction may take place in real time or may only be necessary if conditions are changing in the centers, such as for special events or construction-related lane closures. 

ASSESSMENT

Key Results

TMCs can help reduce incident response times, lower incident rates (mainly secondary incidents), disseminate traveler information and hence reduce congestion and enhance safety. To date there is little data quantifying the exact benefits resulting from TMCs. One study conducted by MnDOT reported decrease in accident rates by 25 percent, 20-minute reduction in response time, 35% increase in average speeds (34 mph to 46 mph) during rush hours and 22% increase in capacity of freeways, after the implementation of their TMC.

Benefits and Costs

Benefits

• Faster incident response and reduction in incident rates.
• Increased safety: Reduction in incident rates and chances of secondary incidents.
• Reduction in non-recurrent congestion.
• Enhanced communication in all aspects of transportation management (planning, design, implementation, operation, maintenance). 
• Monetary savings by sharing responsibilities between fewer staff, achieved by co-location of participating agencies at the center. Special skills, such as database or network administration or configuration management, are only justifiable for such larger facility. 
• Agencies working closely together in a TMC typically produce a more consistent, unified response to a situation, increasing the overall effectiveness of the transportation resources. 

The cost of implementing TMCs vary depending upon the size and functions of the TMC.
Overall costs involve:

• Conception, design and implementation of TMCs.
• Yearly operational costs including the cost for co-hosting the number of agencies present. (For example, the yearly operation budget for Seattle is in the range of  $1.4 million, and that for San Antonio  ranges from $700,000 to $1 million. The Houston TranStar is located in a $11.5 million, 52,000 sq. ft. TMC housing transportation and emergency personnel.)

The challenges that a modern transportation management center face are not confined to implementation alone, equally challenging is its operation and maintenance. 

• The TMC planning, design, and implementation involve not only several departments within the implementing agency (or agencies), but also the efforts of a variety of private sector product and service providers. This requires both significant coordination and ongoing effort to build and maintain consensus. 
• The TMC may be in planning, design, and implementation several years, requiring it to deal with multiple technology generations.
• Often, multiple individuals and organizations are involved in any given transportation situation, with differing (and potentially unclear) roles and responsibilities. These participants may be acting from incomplete understandings of the situation and with differing motivations and priorities. Communication and coordination between the participants is seldom complete. 
• The agency owning the TMC faces a daunting challenge of implementing, operating, and maintaining not only a complex transportation environment, but a mass of complex and rapidly evolving technology. 
• The TMC is often the focal point for monitoring and control of tens of millions of dollars of highly visible transportation resources, on which the surrounding community rapidly becomes dependent. If the system does not work well, the agency's credibility can be negatively  affected in the media and among individual travelers. 

CASE STUDIES

Each TMC currently operating in the United States is unique- varying by size and  functionality.  Some are dubbed Traffic Operations Centers, others Transportation  Information Centers, and others Traffic Systems Management Centers, etc.  Though unique, they all have the commonality of providing some form of traveler information  based on data.  The following table provides Internet links to various operating TMCs in  the United States.
 

City	Internet Link
Houston	http://traffic.tamu.edu/transtar.html
Los Angeles	ITS World Article on California TMC's
Minnesota	http://www.dot.state.mn.us/tmc
Chicago	http://www.ai.eecs.uic.edu/GCM
Seattle	http://www.wsdot.wa.gov/
Phoenix	http://www.azfms.com/About/toc.html
Detroit
San Antonio	http://www.transguide.dot.state.tx.us/atms_info.html
Atlanta	http://www.georgia-traveler.com
Milwaukee	http://www.dot.state.wi.us/dtd/hdist2/monitor.html

Houston, TX

Houston TranStar is a cooperative effort between the City of Houston, Harris County the Metropolitan Transit Agency (METRO), and TXDOT responsible for the management of a variety of freeway and arterial street systems including Intelligent Transportation Systems (ITS) programs, Emergency Management Systems and Enforcement efforts within the Greater Houston area.  TranStar is located in a $11.5 million, 52,000 sq. ft. Transportation Management Center (TMC) housing transportation and emergency
 management personnel. For this reason, Houston TranStar is a fully integrated in terms of  both systems and daily management of personnel and work functions across jurisdictional  boundaries, resulting in a seamless implementation effort.

The TMC includes a central control operations room, a communication room, a telephone switch room, a briefing and operations room for special events and emergency conditions, and three floors of offices for staff of the participating agencies.  The building also contains viewing areas where the public and news media can learn more about the Centers operation and monitor information during special and emergency events. The service area encompasses 5,436 square miles with a population of 4.0 million.

Field components include: a 160 Mile Freeway System (out of  a projected 300 miles); Freeways and Arterial Street Incident Management; Flow Signals at 53 Ramps; Closed circuit Television surveillance (CCTV); Variable Message Signs; 63 Mile HOV Lane System (out of projected 105 miles); Regional Traffic Signal System (2,800 Signals); Intelligent Transportation Systems (ITS) Programs; and Emergency Management Operations for Evacuation and Disasters.

Los Angeles

The Los Angeles TMC is jointly run by the California Department of Transportation (Caltrans) and the California Highway Patrol (CHP). The LA TMC manages 27 freeways, 5,000 traffic sensors embed in the roads, 140 traffic surveillance cameras, more than 130 changeable message signs, 1,000 traffic-controlling ramp meters, 27 freeway advisory radio transmitters, 150 roaming Freeway Service Patrol trucks and some 5,000 emergency  call boxes! All these elements are monitored from 25 multimonitor workstations.

The TMC, which has a surface of 13,400 square feet, is strategically organized into three working stations: 1. computer operators who monitor the freeway's traffic conditions minute to minute 2. a group which communicates directly with and manages the Freeway Service Patrol trucks which remove incidents from the roads and 3. a section which dispatches and monitors Caltrans' repair and work crews who remove freeway debris, spills and other road blocks.

During a typical month the TMC handles 104,000 "incidents" including 20,000 accidents, removes 20,000 traffic hazards and comes to the aid of 10,000 stalled or failing vehicles. During a typical month about 120 Sig Alerts (warnings of very serious traffic conditions due, for example, to a shutting of a freeway ramp, or freeway for accident removal).

Minnesota

The MnDOT traffic management center (TMC), constructed in 1972, receives data from roadway sensors on about 70 percent of the Twin Cities Metropolitan Area Freeways.  There are currently more than 3,000 sensors gathering traffic flow and congestion levels on 175 miles of freeway in the metro area.  The information is transmitted back to the TMC every 30 seconds over a network of copper twisted pair and fiber optic cables, and placed in a real-time data base.  The TMC is a key player in incident management as TMC staff detect and verify incidents using closed circuit television cameras.  Staff respond to an incident by coordinating emergency response personnel who work closely with the State Patrol.  TMC staff  broadcast traveler information via highway advisory radio to minimize the effect these incidents have on the freeway system. They also coordinate their  activities with the State Patrol, county and city traffic engineers, and transit buses to keep  traffic moving on the arterial roadways during major incidents.

The benefits of the traffic management center have recently been quantified by the MnDOT in terms of safety and congestion reduction. Accident rates decreased by 25 percent (421/year to 308/year) and there was a 20-minute reduction in response time to incidents. Average speeds increased by 35 percent (34 mph to 46 mph) during rush hours  and capacity of Freeways increased by 22 percent.

Chicago

The Gary-Chicago-Milwaukee (GCM) Corridor Transportation Information Center (C-TIC) functions as a "super TMC" serving the greater metropolitan areas of Gary, Chicago, and Milwaukee as well as portion of southeast Wisconsin, northeast Illinois, and northwestern Indiana.  Information from a variety of transportation related sources is collected in each states traffic management center (TMC), and forwarded to the C-TIC where the complete information is sent back to the individual TMCs. The advantage of such as system is that each state is allowed to manage its own system, but it now will have better information on  traffic conditions on facilities adjoining its system, thus creating a seamless transportation  network.

Seattle

Located in downtown Seattle, the WSDOT Traffic Systems Management Center (TSMC) receives data from a network of about 200 CCTV cameras mounted on poles, and traffic counters embedded in the roadway at about half-mile intervals on major Seattle area freeways.  The video and count data is transmitted via modem to the TSMC every 20 seconds over a fiber optic cable network connecting field communication hubs to the TSMC.  Copper wires connect the field devices to the communication hubs.  The data is than used to provide real-time traffic and construction information to the public 24 hours-a-day via variable message signs, highway advisory radio, and the Internet.

The field components of the TSMC include: over 1500 data sensors, 120 CCTV cameras, variable message signs, and highway advisory radio stations. Freeway flow in the central Puget Sound area is continuously managed via the TSMC. Approximately 71 freeway centerline miles are covered by the system which serves a population of about 3 million in  the  four counties of the Puget Sound Region. (Data is for 1997 and is from State of Washington, OFM Forecasting.) PushMe (Puget Sound Regional Mayday System), is a cooperative effort  among WSDOT, the Washington State Patrol, and a number or private  companies that pilot tested this program to help drivers in distress. It uses Global Positioning Survey (GPS) satellite technology to locate and respond to participating drivers in need of assistance. 

The TSMC is staffed by 2 full-time engineers, 6 part-time student operators from the University of Washington, 1 freeway data analysis engineer, 3 SC&DI engineers, and 3 programmers. Three managers are involved in TSMC operations, 1 full time manager and  2 managers with other duties.

Most system maintenance is done by 2 SC&DI engineers and 1 software engineer.  Four electronic technicians and 1 supervisor are assigned to SC&DI field maintenance.  Field maintenance staff is expected to increase to 5 technicians in 1998.

The 1997 operations budget was $1.4 million. Anything left at the end of the budget period is spent on needed enhancements. Over the last two years (1996 and 1997) an average of $260,000 was spent per year on SC&DI field maintenance.  System maintenance costs are funded by operations dollars.

Source: Washington State Department of Transportation

Phoenix

Constructed in 1991 for the Arizona Department of Transportation, the Traffic Operations Center (TOC) houses freeway management systems components and several other Intelligent Transportation Systems (ITS), including freeway monitoring, a statewide simulcast radio system, a tunnel monitoring system, and an elk alert sign control system.  Single mode, fiber optic communication equipment links field equipment to computer  systems at the TOC.

Detroit

Dedicated in 1994, the Michigan Intelligent Transportation Systems Center (MITS) receives data for 32 miles of Detroit freeways from 11 CCTV cameras and 1,240 inductive  loop detectors.  Coaxial cable provides the communications link from the data collection  devices to the MITS.  Data is then disseminated to the public via 14 changeable message  signs.  An expansion of the current monitoring system to cover an additional 148 miles of  freeways in metropolitan  Detroit is underway.  The MITS consists of 16,000 square feet of  space with administrative offices, and conference rooms.  Relocation of the Michigan State  Police dispatch into the MITS Center is currently proposed in an effort to integrate incident  management efforts in southeast Michigan.

San Antonio

The Texas Department of Transportation (TxDOT) traffic management center, called the TransGuide System, began operations in July 1996.  The TransGuide system focuses on  incident management rather than congestion management.  The TransGuide control room  monitors traffic conditions, controls traffic signals, and allows rapid response to accidents  and emergencies using data from roadway sensors. The project is currently in the first  phase of development in which 26 miles of highway are equipped with roadway sensors,  52 CCTV cameras, and 359 lane control signals. Final development is planned to include  191 miles.   The communications system uses fiber optic cables from fiber hubs located  strategically throughout the system. The yearly operating budget of the TMC ranges from $700,000 to $1 million.

A before and after study was conducted for the TransGuide system, focusing on safety, incident management, and driver understanding and utilization.  The study found that the total accident rate decreased 15 percent for roadways covered by the system in 1995. Accident rates for freeways in San Antonio not covered by the TransGuide system experienced an increase in accidents of 4 percent in 1995. Furthermore, the average response time to incidents improved 19 percent for minor incidents and 21 percent for major incidents in 1995 even though police and motorist assistance staffing levels
 remained the same.  Survey results indicate high driver understanding of the system.

Recent expansions of the TransGuide System have allowed for improved traveler information dissemination. Variable message signs now display travel times and information on upcoming congestion. The TransGuide website provides travel times through common routes, a table-based personal route selector, and a map-based dynamic route builder; web users can also access the messages currently displayed on variable message signs along particular corridors. TransGuide also provides television stations with live traffic videos that can br broadcast to the public.

Sources:

Fariello, Brian. Happy, Texas: The Lone Star State is Out on its Own. Traffic Technology International, Feb/Mar 2003.

Henk, Molina, Irwin. Before and After Analysis of the San Antonio TransGuide System, Phase 1. TRB Paper 971027. January 1997

Atlanta

An advanced Traffic Management System (ATMS) in Atlanta is currently under construction following a successful pilot project, the Traveler Information Showcase.  The Traveler Information Showcase was an advanced traveler information system (ATIS) network in Atlanta from June through September 1996 in support of the Olympic games.   The ATMS is intended to provide the surveillance capability to gather traffic data and the  computer processing means of turning that data into useful information.

Milwaukee

 MONITOR is the Milwaukee area freeway management system, managed and operated by  the Wisconsin Department of Transportation.  MONITOR is comprised of a system of in-pavement detector loops, overhead microwave detectors on bridges, CCTV cameras on 45-foot poles, ramp meters, and overhead variable message signs, all linked to a control center in downtown Milwaukee operated by the Wisconsin department of Transportation. This system uses the CCTV cameras to verify the data collected by the roadway sensors and detectors and to determine the type of incident (i.e., accident, stalled vehicle,
 recurring congestion).  Once the freeway conditions are known, operators in the center transmit messages to variable message signs, advising motorists of upcoming conditions. Early identification of the type of incident also assists in the deployment of emergency  response personnel top the site.

Long range plans will expand the MONITOR network to 1200 miles of southeastern Wisconsin freeways, including all 68 miles in Milwaukee County by the year 2000.  Currently traffic surveillance comprises 50 miles of loop detectors embedded in the freeway pavement.  En-route driver information is provided by 14 variable message signs,  and 60 ramps are currently metered.

Link to TMC functions and participants

More information is available on TMC's in the following on-line reports from the ITS JPO office. These reports were published in October 1999. 
 

  Metropolitan Transportation Management Center - Concept of
  Operations: Arizona TrailMaster
                                                           10943
  Metropolitan Transportation Management Center - Concept of
  Operations: Boston Central Artery/Tunnell Integrated Project
  Control System
                                                           11063
  Metropolitan Transportation Management Center - Concept of
  Operations: COMPASS
                                                           10944
  Metropolitan Transportation Management Center - Concept of
  Operations: Houston TranStar
                                                           10963
  Metropolitan Transportation Management Center - Concept of
  Operations: Long Island INFORM
                                                            10983
  Metropolitan Transportation Management Center - Concept of
  Operations: Michigan Intelligent Transportation System
                                                            11103
  Metropolitan Transportation Management Center - Concept of
  Operations: Milwaukee MONITOR
                                                            11123
  Metropolitan Transportation Management Center - Concept of
  Operations: Georgia NaviGAtor
                                                            11124
 Implementation Guides

Transportation Management Center Concepts of Operations:
  Implementation Guide
                                                            11494

Author: Indu Sreedevi