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8.0 Communications
8.1: Introduction8.2: General Considerations
8.2.1: Role of Communications8.3: Overview of Communications Systems
8.2.1.1 Managing Everyday and Emergency Functions8.2.2: Transit Communications Goals
8.2.1.2 Coordinating Activities
8.2.1.3 Functioning as an Asset and a Security Tool
8.2.3: Transit Communications Capabilities
8.2.4: Interoperability
8.3.1: Wireless Systems8.4: Threats to Transit Communications
8.3.2: Wireline Systems
8.3.3: Operations Control Centers (OCCs)
8.3.4: Public Communication Systems
8.3.5: Systems for Interoperability
8.4.1: Physical Damage to Agency Equipment8.5: Protection Strategies
8.4.2: Loss of Power
8.4.3: Communications Failures Outside the Agency
8.4.4: Network Failure from Excessive Demand
8.4.5: Cyber Attacks
8.5.1: Hardening and Access ManagementTable 8 1. Security-Oriented Design Considerations for Communications Systems
8.5.2: Redundancy
8.5.2.1 Redundancy by Duplication8.5.3: Backup Power Supply
8.5.2.2 Redundancy by Variety
8.5.4: Prioritization Service and Dedicated Landlines
8.5.5: Network Security
8.5.6: Design Solutions
Most transit agencies use communication systems every day in a multitude of capacities to better serve and protect passengers and employees and to ensure the continued operation of transit service.
How is this chapter useful? For transit managers it is a resource for:
For security staff it is a resource for:
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This chapter reviews:
- General communications concerns for transit staff
- The role of transit communications in promoting security and emergency response
- Design-related security measures for transit communications systems
- Threats to transit communication systems
- Protection strategies for communication systems
Facility security, access management, cyber security, and vehicle security all impact the overall security and capabilities of a transit agency's communications system. Many of these topics are addressed in other sections of this document, and are cross-referenced where applicable.
Each transit agency should consider how best to integrate diverse elements of a security program to support the agency's security goals.
8.1 Introduction
In a transit agency, communication system assets include all of the stationary and mobile elements, including control centers, transmission towers and signal repeaters, in-station systems, on-vehicle systems, and handheld personal devices.
In light of the potential for a system attack or other destructive event, agencies should consider their level of reliance on communications systems and agency resilience to attack. Agencies should also consider how well they can communicate accurate, timely information when reacting to an emergency event:
- Within an agency to allocate resources and prioritize responses
- With other emergency services to coordinate a response
- With the traveling public to keep them aware of service interruptions and changes in service
The relationship between communications and security
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Emergencies provide a significant challenge to current telecommunications systems, particularly since technology may be compromised at the very moment that the demand for information is greatest. In addition, most transit agencies do not have the ability to directly communicate with other emergency responders.
Transit agencies should consider how to improve methods of communicating during emergencies, both internally and with emergency responders. Transit agencies should also be aware of what other area public safety agencies are doing, or planning to do, to achieve interoperability among their respective communications systems. They may also consider being part of a state or metropolitan area initiative with those area agencies.
8.2 General Considerations
When determining how to improve the security of an agency's communications systems, and how to use those systems to support a transit agency's role in emergency response, there are several issues to consider: the role of communications, goals, capabilities, and interoperability.
8.2.1 Role of Communications
At transit agencies, communications plays a role in managing everyday and emergency functions, coordinating system activities, and functioning as both an asset and security tool.
Security Considerations
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8.2.1.1 Managing Everyday and Emergency Functions
Communications systems are used extensively by transit agencies on an everyday basis and during emergencies. Agencies rely on communications systems to manage the movement of their vehicles, keep staff and passengers informed of changing events in real-time, and coordinate with other agencies. All of these functions are important on a day-to-day basis and are essential for smooth operations; they become even more critical, however, during emergencies and emergency response efforts, when there is a greater likelihood of confusion and timely action may be essential for protecting passengers and staff.
8.2.1.2 Coordinating Activities
Communications are essential for coordinating activity within a transit system. This is true within a single transit agency, as well as between independent agencies that cooperate to support common goals or activities. If a transit agency is to use a systems approach in its everyday operations and emergency response activities (see Chapter 3: Security in the Transit Environment), the ability to communicate effectively among staff members and partner agencies is vital.
8.2.1.3 Functioning as an Asset and a Security Tool
In a transit agency, communications capabilities enable transit staff to conduct normal operations. For this purpose, communications can be viewed as an asset that must be protected from any potential terrorist attack. However, communications are also an important tool that can help an agency respond effectively in case of an attack on any part of the transit system, or an attack elsewhere in the region. For this reason, the continued availability of communications is particularly important during an emergency, especially since transit agencies may also need to coordinate with outside agencies as a part of a coordinated regional response.
This dual role of asset and tool suggests that agencies should explore strategies that make their communications systems more resilient and able to withstand a variety of security events.
8.2.2 Transit Communications Goals
To allocate their resources efficiently, prioritize response actions, and maintain a high level of service, transit agency officials need to be able to effectively communicate:
- Internally, within the transit agency
- Externally, with other agencies including emergency responders
- Externally, with the public
A transit agency's goal should be to maintain communications capabilities with each of these groups, to the greatest extent possible, during everyday operations and particularly during emergency response.
Internal Communications
Transit agencies rely heavily on their communications systems to conduct everyday operations of their services; such as managing vehicle movement, informing staff and passengers about service changes in real-time, and coordinating routine activities with other agencies. A disruption in communications capabilities greatly hinders a transit agency's ability to carry out these everyday activities.
During emergencies, effective communication becomes critical in the different elements of a transit agency being able to respond to events in a coordinated manner, regardless of the type of incident. This is particularly important during unusual events for which there may not be a pre-established protocol, and during situations when portions of the transit system become inoperable and other services must be adjusted to compensate.
External Communications with Other Agencies/Emergency Responders
At the most basic level, agencies communicate with other agencies to obtain information to enable them to make informed decisions about conducting agency activities. This may involve coordinating transit service with other transportation providers, civic agencies with a safety or regulatory function related to transit, or other organizations, or it could be as simple as obtaining updates about road construction that may affect bus routes.
Inter-agency communications become critical in situations when multiple agencies are conducting simultaneous emergency response activities. In almost all cases, all agencies need to coordinate their efforts in real-time. Ideally, this allows the agencies to be mutually supportive, and at a minimum prevents direct interference with each other. Having the capability to communicate directly and easily with other agencies helps a transit agency respond to an emergency effectively and safely.
External Communications with the General Public
Although transit agencies tend to focus on communications capabilities among their employees and with other agencies to promote security and emergency response, they also need to communicate with passengers in vehicles and stations, and with people within the agencies' wider service area. This allows agencies to inform passengers of situations and service changes as they occur, and to direct large numbers of passengers to safe locations during a transit system emergency situation.
Providing a means for passengers to contact vehicle operators or other transit staff enables passengers to inform transit staff of situations occurring in vehicles or stations of which the staff may not be aware. This greatly improves security within the transit system by empowering riders to perform passive surveillance.
8.2.3 Transit Communications Capabilities
To accomplish the transit communications goals in Section 8.2.2, transit agencies would benefit from developing certain core capabilities for their communications systems to support both everyday operations and emergency response efforts in the following situations:
- Between agency facilities and vehicles (voice and data)
- Between the transit agency and other agencies
- Between vehicles and other agencies
- Between passengers and vehicle operator
Between Agency Facilities and Vehicles (Voice and Data)
Transit agencies need to maintain voice contact between vehicle operators and the OCC or other fixed facilities, such as transit stations. This enables staff in both locations to inform each other of evolving situations, and to relay commands quickly.
Data communications with vehicles enable the OCC to track the locations and status of all vehicles equipped with appropriate hardware. In some systems, the OCC is even able to control vehicles remotely. These capabilities greatly facilitate any necessary rerouting of vehicles, and contribute to the prevention of theft and/or unauthorized operation of vehicles. For more details, refer to Section 7.5.8.
Between Transit Agency and Other Agencies
The ability to communicate with other agencies is helpful on an everyday basis, but it becomes critical during emergencies and emergency response. Ideally, a transit agency acts as part of a coordinated citywide or regional effort to evacuate people, to carry emergency response personnel and supplies where needed, and to prevent transit vehicles from inadvertently entering dangerous areas. This is only possible when multiple agencies are able to communicate information quickly and accurately. Voice and data transmission systems not only need to maintain functionality during an emergency, but the independent systems used by different agencies need to be compatible with each other. More information is provide in Section 8.2.4.
Between Vehicles and Other Agencies
While not yet a common feature of most transit vehicles, the ability for a vehicle operator to communicate directly with law enforcement or emergency response personnel might be a more efficient means of addressing transit vehicle situations. This is particularly relevant for buses and other vehicles operating on the road system, where they can be used as part of a flexible emergency response effort. Another option is the ability for personnel from other agencies to access real-time data feeds (e.g., video) from the vehicle, for example in the case of an on-board attack or hostage situation.
Between Passengers and Vehicle Operator
Transit system personnel regularly use on-board public address systems to inform riders about service status. These systems are also crucial for operators to provide instructions to passengers during an emergency. In-station PA systems allow staff to direct patrons to safe locations during an emergency.
Emergency call boxes in vehicles and stations enable passengers to inform transit staff of security-related incidents taking place. This greatly improves system security by involving riders in passive surveillance and enabling them to quickly report incidents to transit staff without leaving the site.
8.2.4 Interoperability
Wireless interoperability is the ability of public-safety agencies to communicate with one another via radio communications systems - to exchange voice and/or data with one another on demand, in real time, when needed.1 Interoperability should be a vital element of communications planning for a transit agency, particularly when planning its emergency response activities in conjunction with other agencies. Yet, it is also one of the most challenging aspects of communications for an agency to address effectively.
"Foremost among the obstacles that can hinder an effective multi-jurisdictional response is the lack of interoperability among public safety agencies. Wireless interoperability is simply the ability of public safety officials to communicate across different wireless systems when necessary. Radio communications are often public safety personnel's only lifeline when operating in a crisis environment. Without communications interoperability, both life and property are put at significant risk." 2
This capability becomes critical when transit agency staff must coordinate their actions with emergency responders from other agencies.
There are several technical obstacles to achieving interoperability, particularly the use of incompatible hardware by different agencies. For more details, refer to Appendix G, "Lessons Learned from Transit Communications Emergencies."
1 National Task Force on Interoperability and Project SAFECOM.
2 The Role of States in Public Safety Wireless Interoperability, Public Safety Wireless Network Program.
8.3 Overview of Communications Systems
Transit agencies use a wide variety of systems to transmit voice and data among their employees and with other agencies. This section provides a brief overview of the types of communication systems used.
- Wireless systems
- Wireline systems
- Operations control centers
- Public communications system
- Systems for interoperability
No one system or set of systems is perfect for all transit agencies. An agency should select a communication system based on the size of the agency service area and staff, budget, and other logistical factors.
8.3.1 Wireless Systems
All wireless systems operate using the electromagnetic spectrum - radio waves, TV waves, and radar - to send signals between devices. These waves are distinguished from one another only by frequency and wavelength.
Systems used by transit agencies include mobile radio communications, low-powered localized transponders, rail vehicle communications and control, and OTS commercial systems and equipment.
Mobile Radio Communications Systems
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| Vehicle-mounted mobile transceiver |
Most transit agencies use mobile communications systems (also known as "mobile radios") in everyday fleet operations. In normal operations these system are used for communicating with the transit vehicle operators, dispatch, monitoring vehicle location and status, vehicle rerouting, and for notification about on-vehicle emergencies.
The system is often owned and maintained by the transit agency, and consists of a base station antenna and transceiver, additional towers ("repeaters") for providing required coverage, and both vehicle-mounted and handheld transceivers. The repeaters consist of a tower-based antenna and often a housing for the transmit/receive equipment; a landline tie to the OCC is typical.
Low-Powered, Localized Transponders
Some transit agencies use low-powered systems for very short-range operational applications. Uses include downloading bus-stored data on passenger counts when the bus returns to the garage, providing bus access to special travel lanes and to facilities like parking lots, and granting traffic signal priority to transit vehicles.
The system typically involves a low-powered transmitter aboard the vehicle that communicates with a fixed-site transponder. The transponder receives the transmitted signal from the vehicle and transmits a response or data back to the vehicle.
Rail Vehicle Communications and Control
A specialized use for short-range transponders is rail vehicle communications and control systems. Some newer transit systems even use such systems for all rail vehicle control, eliminating the need for on-board vehicle operators.3
These systems use a combination of wireless radio frequency (RF) communication, landlines, and commercial cellular digital packet data (CDPD) services for vehicle-to-dispatch communications, train location monitoring, vehicle identification, and emergency remote train control. On trains, data is transferred between a low-powered, on-board transponder and a series of fixed transponders situated at intervals along the rail right-of-way.
Off-the-Shelf (OTS) Commercial Systems and Equipment
Transit agencies often supplement the communications systems they maintain and operate themselves with additional, commercial systems. These OTS systems enable an agency to expand its capabilities without requiring large capital costs for equipment and infrastructure.
These systems include: cellular/mobile phone service, handheld devices and pagers, walkie-talkies, microwave links, satellite phone systems, and wireless fidelity (WiFi) networks.
3 Advanced Public Transportation Systems: The State of the Art Update 2000.
8.3.2 Wireline Systems
Wireline systems (also known as landlines) normally connect two fixed points by transmitting voice and data over wires or cables, either buried or strung along telephone poles. A landline can be a dedicated system owned and operated by a transit agency, or it can be leased from a commercial service.
Systems used by transit agencies include conventional telephone systems, dedicated landlines, and high-capacity landlines.
Conventional Telephone Systems
Conventional telephone systems can be either digital or analog, and are typically routed through commercial operators' landline systems connected to the international network.
Transit agencies use conventional telephone systems on a daily basis for many purposes: voice communications between facilities and with external agencies, fax transmissions, and low-bandwidth Internet connections.
Dedicated Landlines
Some agencies, especially those operating subway and/or light rail service, use dedicated landline services to directly communicate between facilities, without involving a commercial routing facility. Dedicated landlines can be owned and maintained by the transit agency or by a commercial service.
Transit agencies typically use landlines to link remote repeaters with the OCC, to link wayside transponders along rail lines with the OCC, or to establish internal analog phone systems for additional backup. Dedicated landlines can also be part of a rail vehicle control system, enabling the OCC to control the rail system's trackside signals.
High-Capacity Landlines
As transit agencies adopt new technologies for communications, parts of their communications networks rely on high-capacity landlines, which may be agency-owned or leased from private commercial vendors. These include fiber optic cables and other landlines used for high-bandwidth data transmission, computer network connections, data feeds from remote devices such as CCTVs, and Internet connections.
8.3.3 Operations Control Centers (OCCs)
Agencies manage their communications systems from their OCCs. Activities can include communicating with all fleet vehicles, dispatch, ongoing supervision of tracks and signals, vehicle tracking, communicating with external agencies, and coordinating emergency response.
These activities may or may not be integrated into a single, centralized facility. Larger transit systems may have separate OCCs for rail, bus, and other modes. For more information, refer to Section 6.3.3.
8.3.4 Public Communication Systems
Transit agencies must be able to quickly and efficiently communicate information about incidents in facilities and/or vehicles, changes in transit service, and emergency operations to the public at large, particularly riders within their system. Intelligent Transportation Systems (ITS) technology now makes it possible to provide service updates in real time; transit agencies can use these technologies to disseminate information during an emergency:
- Public address (PA) systems (in-station and in-vehicle)
- Variable message sign (VMS) systems (in-station and in-vehicle)
- Emergency intercoms for passenger use (in-station and in-vehicle)
- Service area-wide broadcast methods (transit agency Web site, local media outlets)
8.3.5 Systems for Interoperability
Transit agencies must coordinate with other emergency response agencies to exchange voice and data communications quickly and accurately. Systems used by transit agencies include interoperable voice communications and data-sharing systems.
Interoperable Voice Communications
In most cases, transit agency staff will benefit from establishing wireless voice communications with other emergency responders; since this allows agency staff in vehicles and other non-stationary locations to maintain contact.
The two types of interoperable wireless communications are shared systems on dedicated spectrum used by multiple agencies, and radio communications switches that act as interpreters between incompatible systems. A third option, software-defined radios offering multiple transmission frequencies and formats, will be available in the near future.
Data-Sharing Systems
Many agencies have started to use recently developed data-sharing systems that are improving their ability to exchange data about vehicles, staff, and facility locations in real time with other agencies, and to overlay information from different agencies within a single system.
8.4 Threats to Transit Communications
While a transit agency's communications system is not a likely target for a terrorist attack intended to inflict civilian injuries, terrorists may target a communications system as a means of halting service, of providing misinformation, or of obtaining sensitive information about the system. Communications systems may be also affected indirectly by an attack elsewhere that compromises communications capabilities.
When analyzing threats to a transit agency's communications, agencies should consider threats against physical components of systems and against communications capabilities. These include:
- Physical damage to agency equipment
- Loss of power
- Communications failures outside the agency
- Network failure from excessive demand
- Cyber attacks
Not all of these threats are necessarily caused by intentional actions; some may be the result of accidental extraordinary circumstances, such as region-wide power outages.
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| A broadcast tower |
8.4.1 Physical Damage to Agency Equipment
Direct physical damage to communications infrastructure is one source of failure. The loss of one or more critical pieces of equipment can render an entire system inoperable.
- Example. Damage to towers or repeaters used to broadcast radio transmissions or to the various telephone and communications cables (either buried or strung in the air) with junction connections, could disrupt communications links between the control center and field equipment and vehicles.
Components located in geographically isolated spots may be particularly vulnerable to an attack, since attempts at sabotage are more likely to go unnoticed. However, communications infrastructure may also be destroyed as collateral damage in an attack on an unrelated target, or by accident.
- Example. In the terrorist attacks of September 11, 2001, numerous agencies lost communications capabilities due to the physical damage suffered in the World Trade Center. The Port Authority's central communications system was located in the World Trade Center, and its loss affected operations throughout the agency. The New York City Fire and Police departments also lost radio towers and repeaters located on or in buildings in the World Trade Center complex, which compromised their radio communications.
- Example. During a 1994 earthquake in the Los Angeles area, physical damage to both switching centers and telephone lines disrupted landline telephone use, which was one of several communications challenges that area transportation agencies faced.
8.4.2 Loss of Power
Since most communications technologies require electricity, loss of electrical power-either locally or over a broader service area-can pose a major problem for communications systems such as radio systems, email, Internet, cell phone, voicemail and call sorting, and computer-aided dispatch. Loss of electricity could be the result of an intentional attack or unintentional event, either within the agency or outside the agency, but either case could hinder a transit agency's ability to communicate effectively.
- Example. The Trans-Hudson Emergency Transportation Task Force in the New York area identified communications technology as the leading problem during the 2003 Northeast power outage. Most transportation agencies did not realize the frailty of their technology and thought that they had better backup power than they in fact had. As a result, one major bus agency was without communications between the operations control center and its fleet for over four hours. Several other agencies in the Northeast lost radio communications altogether-either because repeaters failed or backup battery supplies expired-and suspended service as a result.
8.4.3 Communications Failures Outside the Agency
In addition to a power outage, other types of external failures may occur that could affect transit agency operations. Because agencies often use privately owned communications backbones or lines to supplement their own communications systems, a point of failure may lie outside of the agency's own equipment. Externally provided services, such as commercial mobile phone systems, are often an easy way to increase an agency's communications options, but transit agencies should consider system vulnerabilities. Since these systems are outside the control of the transit agency, it can be difficult to ensure sufficient measures have been taken to ensure uninterrupted service.
- Example. A central switching office for a telephone-service provider was destroyed in the September 11, 2001, attacks, and a large number of telephone radio towers and repeaters located atop the Towers were lost, causing a widespread loss of both conventional and cellular phone service in the area.
- Example. In the 2003 Northeast blackout, although equipped with backup power on-site, New York City's 911 system experienced repeated failures due to a loss of power at privately owned switching stations. Similarly, although the communications center at the Suburban Mobility Authority for Regional Transportation in the Detroit area was fully operational, the loss of its commercially provided Internet service provider (ISP) service compromised the agency's ability to schedule para-transit trips using a GIS-based computer application.
8.4.4 Network Failure from Excessive Demand
Networks are designed to carry out certain functions within certain capacity limits. Emergency situations typically generate significant demand for communications services, which can sometimes overwhelm systems even if the equipment is fully functional, especially systems shared with the general public.
- Example. Cingular Wireless, the second largest U.S. wireless carrier, reported a 1,000-percent increase in calls in New York on September 11, 2001. During the 2003 Northeast power outage, one transit agency's communication system was overwhelmed as field staff all tried to communicate with the operations control center at once.
8.4.5 Cyber Attacks
As communications systems become more advanced, they rely heavily on computers and digital networks for their operation. As with all digital systems, these are susceptible to electronic sabotage by hackers and others intent on disrupting operations. Computer viruses, even those not directly targeted at transit agency communications systems, also pose a significant threat.
Transit agencies should consider whether their communications hardware, software, and networks are able to withstand cyber attacks. Further analysis of this issue and corresponding security strategies are beyond the scope of this document. (For more information on cyber security, refer to U.S. Computer Emergency Readiness Team's Web site at http://www.us-cert.gov.)
8.5 Protection Strategies
It is difficult for any organization to prepare for terrorist attacks or other emergencies that might require a coordinated response because such incidents are largely unpredictable. The problems experienced in one emergency may be different the next emergency.
In considering how to protect its communications systems and ensure those systems can respond to an emergency, a transit agency should consider two issues: protecting its physical assets (e.g., communications hardware), and protecting its communications capabilities. Striving to do both will result in a communications system that is more robust and, ultimately, more versatile.
Lessons from prior events suggest the following types of strategies can help protect a communications system from the effects of a terrorist attack:
- Hardening and access management
- Redundancy
- Backup power supply
- Prioritization service and dedicated landlines
- Network security
Each transit agency faces a particular set of circumstances and needs; no single communications security strategy is appropriate for every agency. An agency should consider factors such as its communications needs, threat assessments, budget, and existing systems to determine which of the above strategies best fit its goals. Appendix G, "Lessons Learned from Transit Communications Emergencies" describes two recent emergencies that transit agencies can learn from; the September 11, 2001 terrorist attacks on New York City and Washington, D.C., and the August 14, 2003 blackout across the Northeastern United States.
8.5.1 Hardening and Access Management
The most straightforward approach to protecting a transit agency's communications system is to safeguard the physical components of that system. Preventing unauthorized access to transmitters, relay towers, and computer control centers through access management and perimeter control helps to ensure that the components will not be sabotaged, stolen, or misused. Similarly, reinforcing the components and the structures that house them helps to prevent damage to the components in the event of an attack or similar situation.
Further analysis of access management and hardening techniques is beyond the scope of this chapter; refer to Chapter 5: Access Management and Chapter 6: Infrastructure for information.
8.5.2 Redundancy
An agency should ensure that it has built in sufficient redundancy to survive damage to a part of the system, and should strive for a layered approach to communicating with its major audiences. A layered approach means either having duplicate equipment, so that second-string infrastructure can be utilized in case the usual system becomes incapacitated, or having multiple forms of communications, so that even if one type of communications technology is not working, another might remain operable.
8.5.2.1 Redundancy by Duplication
This type of redundancy helps an agency reduce vulnerability to single points of failure within its communications systems by avoiding reliance on an individual facility or piece of hardware. For example, preparing an alternate antenna system would allow agency communications to continue if the main antenna goes off line because of either manmade or natural events. Agencies should consider locating primary and duplicate equipment in separate locations to reduce the likelihood of both sets being compromised during an event.
Feasibility
The expense of procuring and maintaining duplicate equipment may be beyond the limits of a transit agency's available resources, and may be hard to justify for what might be considered an unlikely event. Off-site locations also imply additional capital and operating expenses. Careful positioning of duplicate equipment may be warranted, depending on the vulnerability of the main communication systems and the criticality of continued communications for operations activities. Each agency should assess duplication within its own unique environment; some systems and equipment might be more worthwhile to bolster with redundancy than others.
In general, equipment that might be feasible and worthwhile to duplicate include:
- Antennas that support mobile (radio) communications
- Essential landlines
- A communications center (see below)
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| A mobile command post |
Alternate Communications Center
A transit agency may consider the purchase and operation of a field-mobile communications center for use in an emergency or large special event, to replace or supplement the primary communications center. This center usually consists of a bus or truck retrofitted to include technology that allows a transit agency to perform its normal operations activities from the vehicle. Installed equipment can include radio communications, satellite communications, computer linkups, CCTV monitoring capability, and telecommunications technology.
- Example. Both New York City Transit and New Jersey Transit used mobile communications centers-transit buses equipped with satellite and computer technology-as command posts for communications and decision making during the September 11, 2001 terrorist attacks, and again during the 2003 Northeast blackout.
Capital and operating costs of a mobile communications center can be high and may only be feasible for larger transit agencies.
8.5.2.2 Redundancy by Variety
This type of redundancy means including different options that might each continue to work under different sets of adverse circumstances. This strategy may offer an agency more resiliency than duplication, because circumstances sometimes might preclude the use of a certain type of equipment altogether.
- Example. In New York and Washington, D.C. on September 11, 2001, immediate communication with agency field staff and emergency responders was difficult because telephone landlines were damaged and mobile communications systems were overloaded or did not provide adequate coverage. In this case, extra landline telephones or cell phones would not been useful, but an independent system such as a dedicated internal phone line might have worked.
In general, prior events show that the more diverse the agency's communications technology options, the better.
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| A range of options can help ensure the ability to communicate with vehicle operators. |
- Example. During the Northeast power outage in 2003, having a range of options proved to be very valuable. While most forms of communications technology-VHF and UHF radio communications, train control communications, cell phones, landline telephones, Internet, and text messaging-worked at certain times during the blackout, none of them were reliable all the time.
Some agencies found that text messaging using pagers and handheld devices was particularly effective for maintaining a communications link between the central office and field staff while network service was spotty. With the loss of power, some agencies lost their landline telephones that operated through a networked system, but those that had dedicated landlines separate from the network were able to continue to operate. For others, the conventional telephone system was their one source of communications that did not go down with the power grid.
- Example. Alternate types of communications also proved valuable when a freight train caught fire in a Baltimore tunnel in 2001. The train crew was unable to contact the operations control center using the radio communications system because there was no radio signal where the incident occurred, but the train crew was able to communicate with the operations center by using a cellular phone after walking toward the tunnel portal.
As with redundancy by duplication, physical dispersion of an agency's different systems might help ensure that not all communications technologies are disabled by the same event.
- Example. In the 2003 Northeast blackout, an agency based in the New York City metropolitan area maintained its ability to batch-fax to partner agencies through its Florida-based faxing service.
Feasibility
While redundancy by duplication may be prohibitively costly, redundancy by variety may be more feasible since there may be inexpensive alternatives that, although not perfect substitutes for a primary system, may be sufficient in an emergency situation.
Handheld radios and pagers can provide a low-cost redundant system for communications among field staff.
- Example. Using handheld radios, NYCT was able to evacuate 400,000 people in three hours during the 2003 Northeast blackout and to ensure staff members were in place at key locations. Such a system is also scaleable, since the number of units purchased and operated can be expanded or reduced depending upon each agency's requirements.
An easy way for agencies to incorporate redundancy is to keep obsolete equipment even after it has been replaced by a newer, upgraded system.
- Example. When the Suburban Mobility Authority for Regional Transportation in the Detroit area lost an ISP connection during the 2003 blackout, an old dialup modem (and backup generators) allowed the authority's communications center to stay connected during the outage.
An agency might consider any combination of the following options to assemble a resilient communications "toolkit":
- A dedicated digital trunked mobile radio communications system
- Conventional and mobile phone service with prearranged priority
- An internal analog phone system
- Dedicated landlines
- Walkie-talkies
- PDAs and pagers
- Backup point-to-point microwave link
- Backup access to a satellite communication service
- Transit agency radio system linked to public safety agencies through interoperability
- Joining an area-wide digital public safety radio system
8.5.3 Backup Power Supply
Since most agency communications equipment requires electricity to function, backup power supplies are essential for any capabilities to be maintained in case of an emergency.
An agency may want to be prepared to support its own mobile radio communications system, on-site computer equipment, and telephone switch. Each agency must assess which systems warrant backup and the amount of necessary reserve power. Agencies have a number of backup power source options, including batteries and generators.
For each piece of communications equipment, the agency should consider the full ramifications of both a brief interruption and an extended outage, in order to be prepared for both types of events. Considering every piece of equipment in different scenarios helps reduce the chances of surprises later. A conventional telephone system may not require power from the grid in order to function, but if an on-site telephone system has a computer-automated call-handler, or if the telephones on-site require electricity in order to function, the agency might not have access to the conventional telephone system during a power outage.
- Example. During the 2003 blackout, transportation agencies learned to keep some low-tech phones on hand and to arrange for a dial-around option that circumvented the computer-automated voicemail system in case of a power outage. Other agencies realized, during an extended outage in August, that computer equipment supported by backup generators would require air conditioning to maintain a safe operating temperature. If computer equipment is supported by backup power, agencies may consider allowing air conditioning equipment to be looped into the backup system if the computers must run for an extended period during hot weather.
In addition to servicing key functions at an agency's communications center, a transit agency should consider which field equipment should also be supported with backup power, if possible.
- Example. Remote towers and transceivers could be equipped with auxiliary power and cabling protection at the main communications towers.
8.5.4 Prioritization Service and Dedicated Landlines
Since communications networks can sometimes be overwhelmed with use, especially during emergencies, transit agencies can ensure their own communications capabilities by arranging for prioritized access to network services, or by obtaining their own internal dedicated phone lines.
The federal government has instituted services that help designated agencies complete priority calls through both the landline and wireless telephone networks. The Government Emergency Telecommunications Service 4 (GETS) and the Wireless Priority Service 5 (WPS) provide pre-approved users with priority routing of landline (GETS) and wireless (WPS) calls during times of emergency and crisis, even during periods of peak demand. GETS and WPS are available to federal, state, and local government agencies, as well as to private companies and organizations, with responsibility for national security or emergency preparedness. On September 11, 2001, and the days following, there were more than 18,000 GETS calls with a completion rate that exceeded 95 percent. During the 2003 blackout, there were about 1,800 calls made.6
Another option is to invest in an internal analog phone system that is not dependent on the commercial telephone system to connect points within the agency or to connect the agency's communications center to essential partner agencies. Dedicated lines may be valuable assets in times when the conventional telephone service is unavailable, or when the commercial telephone system is overwhelmed.
4 More information on GETS can be obtained at http://gets.ncs.gov/.
5 More information on WPS can be obtained at http://wps.ncs.gov/.
6 In its own assessment after the blackout, the City of New York reported difficulties accessing the GETS system. This may have been due to the electrical outages impacting equipment.
8.5.5 Network Security
Transit agencies should consider ways to secure their electronic networks from interference. Different measures might be appropriate for different types of networks. Despite a move to integrate many systems, agencies may elect to keep certain vital systems isolated from any integrated systems. For example, train control and fare management are given special consideration by many agencies.
An in-depth discussion of cyber security is beyond the scope of this document, but transit agencies should consider options for protecting the digital elements of their communications systems. (For more information on cyber security, refer to the U.S. Computer Emergency Readiness Team's Website, http://www.us-cert.gov.
8.5.6 Design Solutions
Table 8-1 lists design options for hardening the communications systems in a transit agency. Potential solutions are organized by the three main types of capabilities discussed earlier in this chapter: internal communications, external communications with other agencies, and external communications with the public. Each option either provides the associated capability or serves to help protect the systems that do.
While there are many possibilities to consider in new design or upgrade options for the system, it is important to also evaluate the feasibility of these design considerations. Given the constrained fiscal environment in which the transit industry operates, it is not sufficient to simply list the technical options that are currently available. In addition to listing design considerations, the table addresses the current state of technological maturity and of the feasibility of those considerations. There are issues of initial cost, available space, and the ongoing maintenance responsibilities that accompany the selection of any of these design options.
Table 8-1. Security-Oriented Design Considerations for Communications Systems
| Design Solution | State of Technology Maturity Scale of 1 (least mature) to 5 (most mature) |
Cost Scale of 1 (low) to 10 (high) |
Design Goal (Detect/deter/ minimize) |
Retrofit | Feasibility Scale of 1 (easy) to 3 (hardest) |
|---|---|---|---|---|---|
| INTERNAL COMMUNICATIONS: MOBILE RADIO SYSTEM | |||||
| Communications System Control Center (Base Station) | |||||
| Mobile Communications OCC with redundant capability | 3 - currently deployed to varying degree by largest transit agencies | Range of 5 to 8 - wide range of costs depending upon technology installed | Detect, Minimize, Deter | Maybe | 3 (expensive, possible space issues) |
| Provide power supply backup generators): UPS, gas, electrical | 4 - mostly mature, with wide range of types of backup power supplies available | Range of 1 to 8 - a wide range of costs depending on type of backup system used and amount of technology protected | Minimize | Yes | 2 (requires routine maintenance) |
| Provide redundant base station antenna* on roof or separate tower | 5 - mature technology, but requires additional infrastructure | Range of 5 to 8 - the costs depend upon whether the agency is able to use its own facilities for the towers | Minimize | Yes | 2 (expensive, possible space issues) |
| Remote (Repeater) Towers, Transceivers | |||||
| Provide perimeter protection to towers/equipment shelter | 5 - mature technology | Range of 1 to 4 - costs can be relatively low | Minimize | Yes | 1 |
| Provide power supply backup | 4 - mostly mature technology | Range of 3 to 8 depending upon how extensive the backup system is and what components are included | Minimize | Yes | 1 |
| Provide protection to antenna to shelter cabling | 5 - mostly mature | Range of 2 to 4 | Minimize | Yes | 1 |
| Provide redundant landline connection to base station | 5 - mature | Range of 3 to 8 depending on the infrastructure requirements; also requires monthly operating costs | Minimize | Yes | 2 (expensive) |
| Mobile Transceivers - vehicle mounted | |||||
| Limit access to devices | 5 - mature | Range of 1 to 4 | Minimize | Yes | 1 |
| Assign emergency channel with push-button access | 4 - mostly mature | Range of 2 to 5 | Detect, Minimize, Deter | Yes | 1 |
| Install silent alarms and covert microphones | 4 - mostly mature and becoming standard installation during bus purchases | Range of 4 to 8; the costs depend upon when the installation (new or retrofit) is done and the extent of the alarms | Detect, Minimize | Yes | 2 (expensive) |
| Mobile Transceivers - handheld | |||||
| Limit access to devices | 5 - mature | Range of 1 to 4 | Detect, Minimize, Deter | Yes | 1 |
| Assign emergency channel with push-button access | 4 - mostly mature | Range of 2 to 5 | Detect, Minimize, Deter | No | 1 |
| Walkie-talkies/pagers | |||||
| Limit access to devices | 5 - mature | Range of 1 to 4 | Detect, Minimize, Deter | Yes | 1 |
| INTERNAL COMMUNICATIONS: LANDLINES | |||||
| Remote Repeaters to OCC | |||||
| Provide redundancy | 5 - mature | 6 - costs involve both capital and ongoing operating costs | Minimize | Yes | 2 (expensive) |
| Along rail right-of-way with linkage to OCC | |||||
| Provide redundancy | 5 - mature | 6 - costs involve both capital and ongoing operating costs | Minimize | Yes | 2 (expensive) |
| EXTERNAL COMMUNICATIONS: WITH EMERGENCY RESPONDERS/EMERGENCY RESPONSE CENTER | |||||
| Interoperable Wireless Communications System | |||||
| Develop common system with emergency response agencies | 1 - a technology that is rapidly evolving but lacks common industry standards | Range of 5 to 10 | Detect, Minimize | No | 3 (spectrum issues, cost) |
| Landline/conventional phone system | |||||
| Use dedicated landlines and conventional phone system | 5 - mature | 2 | Detect, Minimize | Yes | 1 |
| Cell phones | |||||
| Use commercial mobile service | 5 - mature | 2 | Detect, Minimize | Yes | 2 (service availability issues) |
| EXTERNAL COMMUNICATIONS: PASSENGER INFORMATION IN STATION | |||||
| Station Public Address System/Message Sign Control * | |||||
| Redundant hardware and wiring | 4 - mostly mature | Range of 4 to 8 - can be expensive depending upon the station infrastructure | Minimize | Yes | 1 |
| Battery backup | 4 - mostly mature | Range of 4 to 8 - can be expensive depending upon the station layout and installed technology | Minimize | Yes | 2 (cost) |
| EXTERNAL COMMUNICATIONS: PASSENGER INFORMATION IN VEHICLE | |||||
| Vehicle-based Message Sign Control/Crew-Passenger Communications * | |||||
| Intercom in each car allows passengers to communicate with the train crew | 4 - mostly mature | 4 | Detect, Minimize | Yes | 1 |
| Handheld crew radios with comm. switch | 5 | 4 | Detect, Minimize | Yes | 1 |
| On-board PAs and passenger assistance link | 5 | 3 | Minimize | ||
| EXTERNAL COMMUNICATIONS: SERVICE AREA BROADCAST | |||||
| Web-based notifications; TV, radio notifications | 4 - maturing technology seeing increasingly innovative applications | 1- the costs are low | Minimize | Yes | 1 |
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