Challenges for railroad radio
Railroad communications specialists are tasked with implementing data, interoperability and control technologies to improve safety and service. At the same time, they have to conform with revised FRA communications rules and implement a new band plan to cooperate with FCC refarming.
For most business and industrial radio users, simple conformity to the FCC’s operating and licensing rules is the closest their wireless traffic comes to government oversight. If you stay on frequency, inside your contour and under your power cap, then how you use your radio is your business.
Radio communications for transportation, particularly railroads, is more heavily regulated. Railroads face the same technology issues and spectrum-efficiency problems as the rest of wireless users, but their problems are more complex. Although railroads are ostensibly private companies, their activities in providing public transportation for goods and passengers make them subject to detailed industry standards and closer federal scrutiny.
A PMRS licensee, such as a manufacturer, is told by the FCC (or the frequency coordinator): “Thou shalt not exceed certain limits in your coverage. (And if you have dead areas, that’s your problem.)” A railroad is told by the Federal Railroad Administration (FRA): “Thou shalt cover everything you’ve got. (And if you have dead areas, you’re going to have a problem, to the tune of $11,000 a day, until you fix it.)”
Manufacturers and radio dealers that wish to serve this market should familiarize themselves with the challenges the train community faces. Railroad communications specialists are looking for avenues to implement data, interoperability and control technologies. They have to provide conformity to the revised FRA 49 C.F.R. Part 220 rules. And, they have to implement a new band plan to conform with FCC refarming efforts.
Mixed radio environments
Although railroad voice and data communications take place mostly at 160MHz, other frequencies are involved in a growing world of monitoring, alarm and rail safety equipment. In some cases, this brings the FCC to new applications of its delegated authority. Last year, the FRA mandated the installation of “advanced civil speed enforcement systems” (ACSES) in the northeastern U.S. railway corridor. The equipment, first used in Europe, consists of a transceiver and antenna located under the locomotive. It polls transponders spaced along the track bed for safe speed information. Because the equipment operates at 27MHz (used by citizen’s band radio) for polling, and the transponders’ data bursts are at 4.5MHz (civil air patrol use), the railways had to request interim authorization and a rules waiver from the FCC to comply with FRA mandates.
Other railroad initiatives include positive train control (PTC) systems, intelligent transportation systems and GPS/AVL. Some of these applications will doubtless involve satellite communications technology.
Much of the radio infrastructure for a railway system is made up of dispatch centers and maintenance vehicles similar to those found in public safety or public works applications. But the locomotive is a different animal. The working environment for train-mounted railroad radios is filled with ambient noise up to 90dB, vibration and myriad safety concerns. The radio has to fit in a moving workstation filled with other more critical, mission-specific equipment. Headphones and speakers require sufficient frequency range to be audible (250Hz-4,000Hz), and microphones require dynamic range to be sensitive (50dB variations). These levels are necessary to provide output and input of voice communications against the background noise. Headphones may need to be capable of routing cabs alarms that normally issue through speakers, and level amplifiers may be needed. Squelch control with a manual override is also a prerequisite in this environment.
Because of a variety of voice radio disadvantages in this environment, data links have been advocated to make communications safer and more efficient. Voice channels may be congested, because they are also used by yard masters, terminal switching crews and maintenance-of-way crews. This heavy use increases the likelihood of miscommunication between dispatch and the train c rew (and FRA regulations require any garbled radio message to be ignored by the recipient). Overlapping signals between neighboring dispatcher districts, incompatible radio systems within dispatcher offices, and malfunctioning or disabled radios in the locomotive are also cited as reasons for increasing the use of data. Low-priority messages that can be diverted to data transmission alleviate voice channel congestion. Because data messages can be displayed by LCD, VDT or other means, the crew doesn’t have to memorize the message, and the information can be saved on the train’s onboard computer. This would eliminate the current FRA requirement to make a hard copy of all radio orders.
However, voice radio communications will still be required for priority communications, such as departures from normal operations or emergencies, and in cases of data system failure. Voice retains other advantages as well. As in public safety communications, train crews get aural cues from dispatch-they can read the speed, intonation and urgency inherent in voice. Broadcast (shared) dispatch also means that the train crew is aware of other activities and potential situations involving other train crews and locations.
Evolving federal regulations
The extent to which mobile radio communications permeates railroad work is not appreciated without a look at federal railroad communications regulations. In the last quarter of 1998, the FRA revised the railroad communications rules in Part 220 of 49 C.F.R. The transition period for adherence to the updated rules becomes complete in two months, July 2000, at which time smaller railroads will have to be in compliance with all sections. Large railroads (greater than 400,000 annual employee hours) fell under the rules in 1999.
A thorough reading of the rules is recommended to anyone providing services to railroad communications. (Many of these rules are reinforced or surpassed by American Association of Railroads [AAR] standards and individual railroad work policies.) Several points deserve specific mention:
c Definitions – FRA has changed the term “radio communications” to “wireless communications,” and added definitions of “working radio” and “working wireless communications” to the regulations. These definitions include the capability to transmit and receive communications between any location in the railway system and the control center (with the aid of repeaters).
c Redundancy – All passenger trains, regardless of the size of the railroad, have to be equipped with a working radio in the occupied controlling locomotive and with redundant working wireless communications equipment.
c Support crews and equipment -Each piece of independently powered maintenance-of-way equipment must have a working radio and the capability to communicate with other equipment in the work group. Each worker responsible for on-track safety of a roadway work group and each lone worker must have access to a working radio.
c Reliability – Every radio, and the redundant equipment, must be tested before starting a work shift, and any non-functioning equipment must be removed from service and replaced. Dispatch must also be notified of failures. Additional rules changes affect radio operating procedures for worker safety.
Refarming and narrowbanding
Railroads operate voice analog FM networks at 160MHz. With 25kHz bandwidths, this gave the industry 91 channels, which are frequency-coordinated by the AAR through its wholly owned Transportation Technology Center Inc. (TTCI) subsidiary. These VHF highband networks are licensed to and managed by the individual rail companies. They are also interoperable for run-through trains and joint operations.
Railroads also have access to three RF channel pairs at 450MHz. These are used for two-way end of train (EOT) devices, which essentially eliminated the need for the traditional caboose. Six channel pairs, licensed to AAR, at 900MHz have also been authorized by the FCC for new electronic train control applications. These 900MHz channels are being used for control and monitoring. For example, digital applications handle work-order reporting and data communications between signal systems and dispatch centers.
In its infamous, extended refarming process to promote narrowbanding, the FCC acknowledged railroads as a special case within the industrial pool (based in part on the safety applications of railroad spectrum) and allowed the railroads to retain exclusive frequency coordination. AAR is also one of only three frequency coordinators that have entered into a Memorandum of Understanding with the FCC’s Enforcement Bureau to prescreen and attempt to resolve interference complaints among its own industry users.
Refarming presents both opportunity and challenge for the railroad industry. It will allow railroads to double their number of channels, use trunked networks and restructure channels to accommodate present and future communications needs. However, the challenge will be to perform those functions correctly to avoid technical errors and expensive solutions.
Refarming requires that new FCC type-certified radios meet 12.5kHz channel width requirements. Railroads can continue to use 25kHz radios already in service. For the railroads, refarming has meant an increase in the number of channels at 160MHz from 91 to 182, requiring a new channel plan. To enable refarming, and to provide for data capability, AAR created a Wireless Communications Task Force (WCTF) that developed a band plan that has been accepted by the FCC. The plan calls for 10 eight-channel duplex, trunking blocks bracketing a 52.5kHz band that could be used for simplex communications. The eight-channel blocks would be located at base stations, and both the transmit and the receive channel would be located at repeater sites.
The WCTF has also selected Project 25 (TIA-102) technology for use by the railroads as an interoperable, integrated voice-plus-data standard. The Project 25 standard is being used in a pilot program funded by the FRA through the Oregon Department of Transportation. The study will evaluate the technology as a potential VHF data link for train control operations.
Interestingly, railroad-provided Project 25 radios were used by the NTIA’s Institute for Telecommunication Sciences in 1998 to evaluate the audio quality of radios conforming to the standard. Therefore, the railroad industry may find the sensitivity and speech quality assessments of that report particularly useful.
The FRA, in its oversight role, wanted to ensure that railroad communications would not be degraded by adoption of the WCTF band plan or by the use of Project 25 technology. It commissioned the ITS to assess the technology and the rechannelization plan in terms of equipment performance, channel assignments and system capacity, interference issues and radio coverage. One recommendation of that report was to avoid adjacent-channel interference and intermodulation interference that might be created by co-location of multiple channels and frequency assignments. Because Project 25 radios are designed with 12.5kHz bandwidth, but railroad VHF channels are spaced every 7.5kHz, the ITS study recommended that transmitters in neighboring regions be offset in frequency by at least two channels.
TTCI is also developing a “Frequency Application and Management System” to deal with an increasing volume of frequency coordination requests and cut administrative costs.
AAR/TTCI and the North American Joint Positive Train Control Program are also cooperating to develop a “spectrum management tool kit.” The software will use algorithms and database applications to predict the coverage of radio transmission stations using various frequencies, modulation techniques, antenna types, tower heights and transmitter power ratings. The tool kit will integrate geographic information system (GIS) technology for mapping antenna locations and rail lines, as well as estimated RF coverage.
Railroads are actively pursuing the goals they need to modernize and improve radio communications. The radio industry now must support their efforts.
Selected references
1. Multer, Jordan, Robert Rudich and Kevin Yearwood, “Human Factors Guidelines for Locomotive Cabs,” Federal Railroad Administration, Nov. 1998. 2. Moody, Howard, Robert Gallamore and Edwin F. Kemp, “Radio Frequency Management: What is Going on in Railroad Radio Communications?” AAR Transportation Technology Center Web site, www.aar.com/TTC/Communications/comm.html.
3. Vanderau, John M., “Delivered Audio Quality Measurements on Project 25 Land Mobile Radios,” Institute for Telecommunication Sciences, NTIA, Report 99-358, Nov.1998.
4. Vandeau, John M. and E. J. Haakinson, “An Evaluation of the Proposed Railroad VHF Band Channel Plan,” Institute for Telecommunication Sciences, NTIA, Report 99-370, Sept. 1999.
5. “Implementation of Positive Train Control Systems,” Report of the Railroad Safety Advisory Committee to the Federal Railroad Administrator, FRA, September 1999.
