North American railway signaling

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North American railway signaling is dictated by the Association of American Railroads (AAR), which is a trade association of the railroads of Canada, the USA, and Mexico. Their system is loosely based on practices developed in the United Kingdom during the early years of railway development. However, North American practice diverged from that of the United Kingdom due to different operating conditions and economic factors between the two regions. Among the distinctions are:

• The US has a much longer history of power operation of switches (points in UK parlance) and signals.
• The US and Canada departed from UK practice wherein a semaphore blade is devoted to each route; American practice is to group routes by speeds and use a single blade for, say, "medium speed" regardless of the number of routes involved. The primary exception to this situation is in the field of heavy rapid transit, such as Subways and Elevated Lines, which make use of a localization of the British practice, or a combination of the AAR and British systems.

Contents 1 History Of Railroad Operating Rules 1.1 Mergers And Operating Rules 1.2 Questions 1.3 Findings 2 Timetable operation 2.1 Timetable and train order 3 Modern signaling in the U.S. 3.1 Automatic Block Signals 3.2 Rule 251 3.3 Track Warrant Control 3.4 Direct Traffic Control 3.5 Form D Control 3.6 Centralized Traffic Control 3.7 Signaling enhancements 4 References

[edit] History Of Railroad Operating Rules

^[1].

In railroad operations, nearly every aspect of employee behavior is governed by operating rules. Employees who perform their jobs in an unsafe manner usually violate operating and safety rules. Human-factors related incidents are caused, or influenced by, unsafe work behavior and attitudes, as opposed to non-behavior related factors like inclement weather or undetected faulty track. Therefore, nearly all human-factor incidents and injuries can be associated with one or more operating or safety rule violations.

By the 1850’s, railroad operating rules, often printed as pamphlets or on the back of a time card, had evolved to near universal application. On 1887-04-14, representatives of 48 railroads voted for the adoption of what is now known as the Standard Code of Operating Rules (SCOR), published by the Association of American Railroads (AAR). Thus, all railroad rule books in North America today have as their foundation the SCOR in both development and application (Shaw, 1978).

The SCOR, however, was never intended to be used as a working rulebook. Rather, its primary intention was to standardize operating practices to the extent practicable while still preserving the flexibility of individual railroads to either modify or omit rules at their discretion. Even rulebooks with identical phraseology could be interpreted and applied differently on different railroads. Although used as a reference book, the SCOR was primarily a matrix document, from which the industry could establish standard verbiage and a common numbering system. Until recently, in fact, railroads rarely deviated from the original numbering system. (D. Yachechak, personal communication, March 1997).

At present, most Class I railroads in the U.S. use one of two “standard” rulebooks: the Northeast Operating Rules Advisory Committee (NORAC) rulebook and the General Code of Operating Rules (GCOR). Conrail, Amtrak, and several commuter and short line railroads in the northeastern United States use the NORAC rulebook. The GCOR is used by every Class I railroad west of the Mississippi River, most of the Class II railroads, and numerous shortline railroads. A few railroads, including CSX, Norfolk Southern, Illinois Central, and Florida East Coast, have adopted their own rulebooks.

Research indicates unsafe work behavior can be influenced by any number of factors, including temperature, workload, time of day, and specific job tasks to name a few (Ramsey et al, 1983). Unsafe work behavior has also been linked to the organizational culture and to organizational processes (Andrews, 1997; Marske, 1997). Consequently, before unsafe work behaviors in railroad operations can be reduced, some of the reasons employees do not comply with railroad operating rules must be understood. Also, there must be an understanding of some of the cultural components of rule compliance within the railroad system, particularly the development of railroad rules, and how that culture interacts with unsafe work behavior.

[edit] Mergers And Operating Rules

Mergers of major railroad companies in recent years resulted not only in the merging of different railroad lines and operating rulebooks, but also in the merging of railroad cultures and operating practices. Superficially, it may appear that most railroads have adopted a common code of operating rules, but major differences still exist in the application, and consequently, the compliance with these operating rules. Moreover, different management styles often clash when organizational cultures merge, as documented in the case of the Penn Central merger in 1968 (Daughen and Binzen, 1971) and the Burlington Northern Santa Fe merger in 1995 (Machalaba, 1997). This leaves operating rules managers uncertain as to how specific rules should be applied on their newly-formed railroad. Different management philosophies may also influence different compliance standards across railroads.

As railroad operating environments become increasingly complex - from mergers, new technology, and other external forces - operating rules will continue to change in both number and frequency. The number of operating rules and procedures that employees must now commit to memory is substantial. With fewer employees to handle the same workload, individuals may no longer have the time to look up rules when performing their duties, perhaps further complicating both their ability and their desire to comply with these rules.

For years, the FRA has been recommending the standardization of operating rules and practices for cost-effectiveness in both safety and efficiency. In 1992, the American Association of Railroad Superintendents (AARS) convened a special committee, which suggested to its Board of Directors, Executive Council, and membership that “the AARS sponsor a full conference on the standardization of railroad operating rules, practices, and procedures, and that this conference be conducted on the highest level possible, with the full and complete endorsement and involvement of chief operating officers (Gamst, 1993).” A standard set of operating rules, it was argued, would minimize the confusion that exists when employees operate over joint lines and are governed by two rule books instead of one. Of particular concern are situations where different operating rules govern identical, or similar, signal aspects on different railroads.

Some railroad operating officials believe standardized railroad operating rules would have a positive impact on the railroad industry in fundamental and important ways, including:

• increasing the mobility and ease of transition for both railroad employees and managers when transferring from one railroad to another;
• reducing training costs and operating rule development;
• improving safety practices when railroads and railroad rule books merge; and
• improving the overall railroad delivery system across interchange points, regions, and yards.

In response to pressures for standardization, the railroads governed by both NORAC and GCOR recently hired consultants to rewrite and reorganize their operating rulebooks. Two major benefits are expected from these new versions of the operating rule book: 1) an improvement in the clarity and understanding of operating rules, and 2) an improvement in the ability of an employee to look up unfamiliar operating rules.

The extent to which these and other benefits have been obtained, however, is uncertain. Even if the revised rule books enhance the clarity and understanding of operating rules, other important questions still remain. Given a factual understanding, how well are employees able to conceptually apply the rules? How often do operating employees purposely violate rules, even when they understand them and know how to apply them? What influences operating employees to knowingly violate operating rules? How often do rule violations lead to incidents or injuries that otherwise could have been prevented?

Some railroad operating officials urge that both GCOR and NORAC should be used as the SCOR was originally used. They say operating rule books should be used as a basic guide to standardizing operating practices, while still preserving the flexibility of individual railroads to either modify or omit rules at their discretion. If standard operating rules are not needed, the major question that remains is whether or not a process has been established for maintaining quality in operating rule development. This is especially important with the implementation of constantly changing equipment and train control technology, which will force the need for more rapid rule changes. Therefore, the question that must be asked is whether or not guidelines are needed for the development, writing, testing, application, and representation of operating rules. What kinds of guidelines should be developed, if at all? If necessary, what should be the process for developing those guidelines? For this purpose, a focus group was assembled.

[edit] Questions

Pilot questions were developed for the Focus Group, and were distributed to operating rules experts for comment prior to holding the focus group session. These pilot questions were then revised for use during the actual focus group. The resulting questions were carefully selected and phrased to stimulate thoughtful and spontaneous communication among the participants. Although the moderator posed follow-up questions, the following five questions were used as foundation questions for the focus group:

• Q1: What are some of the major types of railroad operating rule compliance problems that lead to serious incidents or common personal injuries?
• Q2: How has railroad management achieved rule compliance?
• Q3: What have been some of the major roadblocks in achieving rule compliance?
• Q4: What have been some important guidelines established among management for achieving rule compliance?
• Q5: Do you see a need for developing a common set of guidelines on rule compliance, made available to all railroads?

[edit] Findings

Note: The following findings are summarized from the opinions expressed during the focus group session and follow-up conversations with participants. These findings are not necessarily in order of importance.

• Question 1: What are some of the major types of railroad operating rule compliance problems that lead to serious incidents or common personal injuries?

• • 1. Restricted speed.

The original definition of restricted speed, which first appeared in the Association of American Railroads SCOR in 1924 (Yachechak, 1996), is as follows: “Proceed prepared to stop short of train, obstruction, or anything that may require the speed of the train or engine to be reduced.”

NORAC currently defines restricted speed as “Prepared to stop within one-half the range of vision — short of a train, obstruction, or switch improperly lined. Be on the lookout for broken rail. Speed must not exceed 20 MPH outside interlocking limits, or 15 MPH within interlocking limits. This speed applies to the entire movement.”

The General Code describes restricted speed as follows: “When a train or engine is required to move at restricted speed, movement must be made at a speed that allows stopping within half the range of vision short of: train engine, railroad car, men or equipment fouling the track, stop signal, or derail or switch not properly lined. The crew must keep a lookout for broken rail and not exceed 20 MPH.”

Restricted speed was the first topic discussed when the focus group was asked about rule compliance problems. Some of the most common violations of restricted speed reported include failure to comply with stop signals, run-through switches, and run-over derails. One person noted that he thought many people tended to apply restricted speed in terms of miles per hour rather than generally being prepared to stop.

It was also noted that restricted-speed violations rarely occurred in isolation. Rather, a series of violations usually occurred that would lead up to a restricted-speed violation. For example, a train dispatcher may have failed to provide requested blocking protection for workers within restricted-speed territory, resulting in a train colliding with equipment on the track while operating under 20 MPH. Although the engineer was operating the train under 20 MPH, as is required by the restricted-speed rule, workers or equipment on the track may not have been anticipated. Not being able to stop within one-half the range of vision was a clear violation of restricted speed. On the other hand, the dispatcher did not provide proper blocking protection to the workers on the track. In this case, two rule violations occurred and both the engineer and dispatcher were partly to blame for the incident.

Accident^[2] data from FRA’s 1996 Accident/Incident Bulletin support operating managers concern about restricted-speed accidents. In fact, the vast majority of human-factor train accidents (85%) occur under 10 MPH. 96% of human-factor train accidents in the yards and 93% of human-factor train accidents on industry/sidings occurred less than 10 MPH. More than half (55%) of human factor train accidents on the main line occur under 10 MPH, 75% under 20 MPH. More than 50% of all derailments and collisions occurred under 20 MPH.^[3] Nearly 40% of main line derailments, regardless of cause, occurred under 10 MPH. Over one-fourth of the collisions occurred under 10 MPH. All human-factor collisions and derailments that occurred under 20 MPH are considered violations of restricted speed.

• • 2. Compliance with radio rules.

Focus group participants agreed radio rule compliance was a common operating rule violation, and the problem was lack of enforcement. Radio miscommunication and misunderstandings, for example, have lead to serious incidents. Instructions such as “High ball, everybody’s in the clear,” without train or unit number identification, could potentially cause a fatal accident. If a crew who overheard those instructions assumed that message was for them and began proceeding, they might operate in such a way that could lead to a collision. In the FRA’s 1996 Accident/Incident Bulletin, however, improper radio communications accounts for less than one percent of human-factor train accidents.

Other examples of improper radio communications can be simply described as “assumptions.” For instance, when crews do not properly identify their train or engine number, other operating crews or workmen may make assumptions about which train the message applies to without confirming the train’s identity. Of particular concern were situations in which crews left main line switches open (not lining back a switch for the main line movement) to expedite trains, transferring the responsibility to another crew. When a train leaves a yard switching track as to the main line, the crew on that train often has the responsibility to line the switch back to the main line. With cabooses no longer being used, and no one at the rear of the train, the engineer must now stop the train when it is past the main line switch, then wait for the conductor or brakeman to walk back up to the head end again (sometimes up to a mile and one-half). This can cause considerable delay. To expedite movement, the responsibility for lining the switch back to the main line is often turned over to someone from another crew still working in the yard.

Incidents happen when the yard crew with the responsibility to line the switch for the main track does not do so, for one reason or another. Another crew on a train that is approaching the switch on the main track will often assume that the track is lined for the main line, which it usually is, and may run through the switch when it is not lined properly. This can cause extensive damage to the switch requiring immediate repair. If the train crew does not realize they ran through the switch, or does not tell anyone for fear of being disciplined, it could easily cause a serious derailment or personal injury the next time a train goes over the switch. While the crew of the train that ran through the switch is responsible for violating the restricted-speed rule (i.e. “…prepared to stop…”), other violations and assumptions occurred prior to this violation, which were important contributing factors that led up to the incident.

• • 3. Securing equipment.

Some focus group participants felt securing equipment was not taken seriously on many railroads. One individual commented that, “There’s a lot more [trains and engines] that are running away that nobody knows about because if there’s no harm, no problem…it’s the attitude I see that’s the problem.” Failure to provide sufficient hand brakes accounted for almost 5% of the human-factor accidents, (FRA 1996 Accident/Incident Bulletin).^[4]

• • 4. Failure to provide proper blocking protection.

Providing proper blocking protection was another concern mentioned, especially if a train dispatcher or operator does not provide the proper authority to operate a train within certain track areas when requested. Proper block protection is required by railroad operating rules, but no causal category is assigned on the FRA accident/incident reporting form.

• Question 2: How well has railroad management achieved rule compliance?

• • 1.Random drug and alcohol tests.

Most participants agreed that random drug and alcohol tests have probably had the largest positive impact on railroad safety over the past several years.

• • 2.Annual rules tests.

Annual rules exams were considered an effective method of reinforcing important safety rules, “raising the level of awareness of the rules.” Creating real world tests and good instruction were suggested for annual rules exam. Good instruction provides a basis for understanding rules. Annual exams were perceived as a good opportunity to discuss critical safety issues that surfaced in the past year. Annual exams also become an important means of information gathering for the rules examiners, helping them keep in touch with problems out on the road.

• • 3.Efficiency tests and supervisor observations.

Many participants felt that the method for conducting efficiency tests^[5]. should be improved, and be used more as a non-punitive learning tool rather than as a punitive device. Supervisors should be visible, they said, and make regular observations with immediate feedback. When supervisors are out in the field, for example, it is easy for them to identify and immediately correct improper radio procedures without taking punitive action. Daily positive face-to-face interactions were critical, they felt, for effective management of rules compliance. As one participant explained,“People for the most part want to understand how to do their job correctly. And sometimes, especially with the new employees, just someone to take them aside and talk to them and explain to them how to do it correctly…they will follow. The old hand, the guy who’s been at it for a number of years, takes a different type of coaching. But I don’t think we need to approach people punitively.”

Participants generally encouraged the use of quality efficiency tests, with a caution not to rely on quotas and numbers when conducting efficiency tests. Supervisors should do something that “challenges the employee to put on his thinking cap and respond to a situation.” There was also an expressed interest in teaching some of the first line supervisors how to do quality efficiency testing. “Not ten tests a month, or a quarter, with each rule being a test. That’s not ten tests. That’s one test. People are going back to big numbers for the FRA…Make a quality test. Make the test mean something. Don’t rely on quotas and numbers.”

• • 4.New employee training.

Some participants felt introductory rules classes for new employees should be followed by field training, then follow-up testing, for two reasons: 1) “Old heads” in the field provide immediate feedback about the procedural aspects of work rules and acceptable safety behaviors, reinforcing and elaborating classroom training, and 2) new employees often bring back to supervisors vital information about common safety practices and safety violations from the field. This information is often difficult to obtain, since most train operations are unsupervised.

• Question 3: What have been some of the major roadblocks in achieving rule compliance?

• • 1.Ambiguous communications.

“Mixed signals” were described as a major barrier to rule compliance. In the opinion of the participants, it appears that a culture has been created on some railroads which fosters a tendency for supervisors to send confusing messages to operating employees - ambiguous messages that imply they should comply with operating rules under some conditions and not comply under others.

Also, different levels of employees appear to have different motivations and pressures to not comply with the rules at times. Yardmasters, train masters, and train dispatchers, for example, may be urged by their supervisors to get the train out of town, and indirectly encourage employees to cut corners on rule compliance to speed up operations. Conductors or engineers may send similar messages to their brakemen.

One participant explained it like this. “It’s a militaristic environment, really, that the railroad runs under. And the fact is that you have commands that come down from the top. And most of the time in transportation those commands are to move the trains. And to get the train from A to B in a certain amount of time. And when you’re not doing it, you know, to the requirements that come in to that…the operating rules, or whatever, get overridden by that command.”

Another participant followed up by saying “What happens is our supervisors forget, and our general managers and our superintendents forget, that the real command that comes down first is Safety First. When they lose sight of that because of equipment priorities, you have a supervisor…now this takes you up to a V.P. or higher, who says now you either meet goals or I’ll find somebody who will. That’s when the real mixed signal comes in. Now…now you’ve taken people who are supposed to be managing people, who are supposed to be producing for us, and they don’t really know which way to turn.” Still another participant explained that “You still have a whole climate of people [operating employees] out there who are convinced that the only reason you’re interested in safety is the bottom line of the company.”

• • 2.Ignorance of responsibilities.

Ignorance of responsibilities seemed to be a common denominator in how these mixed signals, or mixed communications, get disseminated. It was also noted that many yardmasters, dispatchers, and operators are sitting with computers and telephones and have very little face-to-face interaction with the employees they directly supervise. Some complained that people in these jobs often do not realize they are actually supervisors and that they have an important role in communicating rule compliance.

• • 3.Employees’ desire for short cuts.

Employees are often motivated to get the job done quickly. Many factors can increase employee motivation to violate, or bend, operating rules. If it is too cold or too warm, there may be a desire to operate unsafely if it will reduce their discomfort. Similarly, getting a train to a terminal in less time often has little or no impact on one’s wages. Consequently, the sooner one gets the job done, the more money they effectively make per hour. However, once an employee starts overtime, the desire may be to stretch out the time it takes to perform an operation as long as possible. In either case, safety becomes secondary. When these personal motivations are coupled with supervisor requests for increased productivity, both of which could encourage a bending of the rules, participants believe unsafe behaviors are much more likely to follow.

• • 4.Too much paperwork.

A reduction in the workforce seems to have had an impact on midmanagement as well as on operating crews. As one focus group participant said, “…what is really happening is that there are fewer trainmasters, fewer roadmasters. Paperwork is killing them. It’s keeping them at the desk. And they’re working 28 hours a day, instead of maybe 18 or 16 like we used to.”When this happens, the quality of supervisor observations is reduced. Safety-related errors are also more likely to occur when operators, dispatchers, and yardmasters are overloaded with tasks previously performed by someone else. Additional clerical staff, they said, would significantly remedy this situation.

• • 5.Lack of enforcement.

One participant described lack of enforcement this way. “We know when guys are taking shortcuts. No mistake about it. We know it. Question is…are we responding to it? And are we consistent enough in our discipline approach?”

In follow-up conversations to the focus groups, two other participants from a major railroad explained that one of the consequences of overloading supervisors with paperwork and other work previously completed by administrative staff, is a problem with enforcement. Supervisors are fully aware of the extra work required of them when following-up on observations of noncompliance. Enforcing compliance means discipline, and discipline means lots of time and paperwork. While the supervisors may fully intend to enforce rule compliance, the resources may not always be available to them to perform these functions.

Mixed signals was another reason why management may not enforce operating rules. One participant explained it this way. “I know in most cases that people [supervisors] are not responding as they should. Because of mixed signals. I know that.” Senior management, he says, sends mixed signals to first line supervisors regarding safety and productivity. Consequently, supervisors may be reluctant to enforce rule compliance when rule non-compliance improves productivity, especially if the supervisor perceives little risk in doing so. This tendency may be compounded when perceived rewards are much greater for efficient operations than for safe operations.

• • 6.Required quotas.

Required quotas, some suggested, encouraged supervisors to perform nonessential efficiency tests rather than safety-oriented tests.

• Question 4: What have been some important guidelines established among management for achieving rule compliance?

• • 1.Consistent and equitable discipline.

Participants recognized the importance for consistent and equitable discipline, an approach long advocated by behavioral psychologists. Also, they emphasised reinforcing positive safety behaviors as opposed to punishing unsafe, or noncompliant, behaviors.

• • 2.Immediate consequences for rule violations.

When serious rule violations were apparent, immediate discipline was recommended. There should be no question about the disciplinary consequences of serious rule violations. One or two examples, they said, is all it takes to make this message understood.

• • 3.Positive reinforcement.

Everyone also agreed on the importance of positive reinforcement during or after any employee observations. “When you observe somebody and they do the job well, you just don’t go off and disappear. You need to tell that man that he was observed, and he did a good job today.”

• • 4.Personal contact.

Establishing personal contact and getting to know your employees, it was suggested, helped make this positive interaction much easier. This also fosters a more natural communication process that helps the immediate supervisor identify problem areas with the rules that may be difficult to do with simple observations.

• • 5.Yearly evaluations of critical incidents.

A participant from a small railroad described its procedures for evaluating critical incidents in the preceding year, and then creating a testing program for the subsequent year that tests the compliance of major failures from the previous year. It was suggested that this method of test development helped them keep their rule compliance failures to a minimum.

• • 6.Fostering positive safety attitudes.

People realized that to change unsafe behavior you must also change the attitudes that lead to unsafe behaviors. Rules classes, they noted, were the place to do this. “Until you get the guy convinced on the ground that what he’s doing he’s doing for himself…he’s doing it for his family…then you’re still gonna have the guy not paying attention.”

• • 7.Peer respect toward safety.

One proposal for embedding safety behavior, and thus rule compliance, was to develop a culture of peer respect toward on-the-job safety. “What I’d really like to see you do is apply this to the rest of the rules. Because railroaders, safe railroaders, do things because they’re right. That’s the way to do it in my book…Apply their inner reasons as to why they comply. The very basic of rules.”

• Question 5: Do you see a need for developing a common set of guidelines on rule compliance, made available to all railroads?

• • 1.Guidelines are not needed.

Most participants did not see a need for developing a common set of guidelines on rule compliance, perhaps because they perceived the notion of guidelines as a federal regulation. Following are typical comments to the question about the perceived need for developing guidelines on rule compliance:

“The best guidelines in the world won’t work if you don’t change the attitude of the people who have the rules to abide by these guidelines.”

“I guess what we’re all saying is that we don’t need regulations to comply with the rules.”

“Regulations create rules. More rules creates confusion.”

“Accidents are not caused by existing guidelines. They are caused by non-compliance with guidelines ... it’s non-compliance that’s the problem.”

“So ... somebody else writing those guidelines doesn’t work.”

“You don’t need a bookshelf policy.”

“We don’t wanna get over-regulated.”

• • 2.General guidelines are now in use on many railroads.

Although people disagreed with a need for developing a common set of guidelines for rule compliance, a number of good ideas were recommended that could be included in a handbook of guidelines. Following are typical comments about unwritten practices currently used by some rules managers, which could easily be established as general guidelines:

“It [safety] comes from the top. And it can’t get lost in the middle.”

“Until you get the guy convinced on the ground that what he’s doing, he’s doing for himself…he’s doing it for his family…then you’re still gonna have the guy not paying attention [to the rules].”

“Apply it to their inner logic, their inner reasons as to why they comply.”

“…they [operating employees] may not be aware of the consequences. They can’t envision anybody can get killed by what’s really going on.”

“A lot of first line supervisors have…never been taught how to deal with…pursuing enforcement, or pursuing compliance, I guess.”

“Teach…first line supervisors how to do quality efficiency testing. Don’t rely on quotas or numbers.”

“The discipline has to be understood. And it has to be handled equitably.”

"…not approaching your employee from a punitive point of view, but from a coaching or instructing point of view.”

“When you observe somebody and they do the job well…You need to tell that man that he was observed, and he did a good job today.”

“When you have instructional training you have to have time for questions, for examples.”

“Creating real world tests. Doing things out there in the real world that challenges the employee to put on his thinking cap and respond…”

“…create a testing program for the subsequent year that will test the compliance of those failures in the previous year.”

[edit] Timetable operation

The simplest form of operation, in terms of equipment at least, was operation according to a timetable. Everything was laid down in advance and every train crew knew the timetable. Trains could only operate in pre-arranged time periods, during which they had "possession" of the track and no other train can operate.

When trains were operating in opposing directions on a single-line railroad, meets were scheduled, where each train waited for the other at a point they could pass. Neither was permitted to move until the other has arrived.

The timetable system had several disadvantages. The first was that there was no positive confirmation that the track ahead was clear; only that it should be clear. This system did not allow for breakdowns and other such problems. The timetable was set up in such a way that there should be sufficient time between trains for the crew of a broken-down or delayed train to walk back up the line far enough to set up warning flags, flares and the explosive devices known as torpedoes, which alerted a train crew to a blocked track ahead.

The second problem was the timetable system's inflexibility; trains could not be added, delayed, or rescheduled without publishing and distributing a new timetable.

The third was a corollary of the second; the timetable system was inefficient. To give a little flexibility, the timetable gave trains a broad swath of time to allow for some delay. Thus, the line was possessed by the train for much longer than was really necessary.

Nonetheless, this system permitted operation on a vast scale, with no requirements for any kind of communication that traveled faster than a train. Timetable operation was the normal mode of operation on American railroads in the early days.

[edit] Timetable and train order

With the advent of the telegraph, a more sophisticated system became possible, since the telegraph provided the first system available where messages could be transmitted faster than the trains themselves. The telegraph allowed the dissemination of alterations to the timetable, known as train orders. These overrided the timetable, allowing the cancellation, rescheduling and addition of trains, and almost anything else. Sufficient time had to be given, however, so that all train crews could receive the changed orders.

Train crews generally received the orders at the next station at which they stop, although sometimes orders were handed up to a locomotive "on the run" via a long staff. Train orders allowed train dispatchers to set up meets at sidings, force a train to wait at a siding for a priority train to pass from behind, and to keep at least one block spacing between trains going the same direction.

In North American railway traffic control, a "Y" (yellow) train order gave crews information about track speed (in areas where tracks and bridges needed repair). These were called "slow orders" by train crews. An "R" (red) order dealt with meets, waits and other important traffic control issuse. Orders were flagged at train stations by telegraph operators who signaled using a fixed "order board".

Timetable and train order operation was commonly used on American railroads until the 1960s, including some quite large operations such as the Wabash Railroad and the Nickel Plate Road. Train order traffic control was used in Canada until the late 1980s on the Algoma Central Railway and some spurs of the Canadian Pacific Railway.

Timetable and train order was not used widely outside North America and has been phased out in favor of radio dispatching on many light-traffic lines and electronic signals on higher-traffic lines.

[edit] Modern signaling in the U.S.

U.S. railroads have historically used a far greater variety of signaling systems than other countries. There have never been national standards for signal appearance and operation, so each of the hundreds of rail lines developed its own signaling techniques.

As Trains magazine describes:

This was no problem as long as crews stayed on home territory. But as roads merged, split, and spun off new short lines, and tenant operators such as Amtrak and regional commuter systems came into existence, train crews could find themselves on several different properties in the course of a work week.

The creation of Conrail in 1976 out of the remains of a half-dozen bankrupt railroads only made things worse. It was hard enough to rationalize the systems of the constituent companies, let alone interact with other operators over the dense Northeastern U.S. rail network.

After several years, the situation had become intolerable. Training costs were getting out of hand, because crews had to qualify separately on each road over which they might operate. Having to consult half a dozen rulebooks increased enormously the potential for a disastrous mistake.^[6]

As railroad companies eventually began to standardize their rule books via industry-wide committees, the implementation of signal systems between railroads became, if not standardized, at least more similar. Different legacy systems still in use, however, mean that some signal indications can be shown in several different ways.

While each company is free to modify its operating practices (subject to the Code of Federal Regulations), there are three major groups of railroads that share rule books, and therefore, have similar operating practices. Major railroads on the East Coast have adopted the Northeast Operating Rules Advisory Committee (NORAC) rules. Most railroads west of the Mississippi River, as well as the Canadian Pacific Railway, use the General Code of Operating Rules (GCOR). All other Canadian railroads, including Canadian National, use the Canadian Rail Operating Rules (CROR). (Some railroads, including CSX and Norfolk Southern, still use proprietary rule books.) These rule books specify various methods of operation in both signaled territory and "dark territory," where manual methods of granting track authority must be used.

[edit] Automatic Block Signals

Automatic Block Signal, or ABS, systems consist of a series of signals that govern blocks of track between the signals. The signals are automatically activated by the conditions of the block beyond the signal. If a train is currently occupying a block, that block's signal will not allow a train in the previous block to proceed into the block, or will only allow it to proceed at a speed which allows the train to stop before colliding with the train or another object (also known as restricted speed).

Automatic block signals also detect the status of a following signal. If a signal is displaying a stop indication, the preceding signal will display an aspect that warns the train crew that the following signal may require the train to stop.

ABS systems detect track occupancy by passing a low-voltage current through the track between the signals and detecting whether the circuit is closed, open, or shorted. A train's metal wheels and axles will pass current from one rail to the other, thereby shorting the circuit. If the ABS system detects that the circuit is shorted between two signals, it understands that a train is occupying that block and will "drop" the signals (display a stop indication) on either side of that block to prevent another train from entering. ABS system electronics are also able to detect breaks in the rail or improperly-lined switches, which result in an open circuit. These will also cause the signal's aspect to drop, preventing any trains from entering the block and running the risk of bending, breaking, or overturning the rail and derailing or running through an improperly-lined switch.

[edit] Rule 251

Much of the trackage in the U.S. has been converted to double track, which allows two opposing trains to pass without one having to pull out and stop in a siding. Track under Rule 251 has two tracks, each with a designated "current of traffic" (much like a two-lane road). The track contains signals that operate similarly to ABS signals but that govern movement only in one direction. Like ABS signals, these signals are not controlled directly by the train dispatcher but are instead automatically activated by track occupancy. Rule 251 is mostly used in the dense northeastern United States.

[edit] Track Warrant Control

In Track Warrant Control, or TWC, the train dispatcher issues "track warrants" via radio that authorize the train between two specified limits. The limits are often mileposts or stations. The track warrant may authorize a train to proceed to a station and "clear the main," or enter a siding so an oncoming train can pass. Generally, no more than one train or piece of equipment may be given the same or overlapping limits of authority, unless the movements will be made at restricted speed. While TWC is generally used in dark territory, it may be combined with ABS to enable more than one train to be given the same authority (although this generally only applies to trains moving in the same direction). This reduces the workload of the dispatcher and train crew, as new track warrants do not need to be copied every few minutes to ensure that following trains are not delayed due to running out of authority.

[edit] Direct Traffic Control

Direct Traffic Control, or DTC, is similar to TWC, except that the rail line is divided up into predefined blocks--somewhat similar to ABS blocks without the signals--and dispatchers authorize trains to proceed in a specified number of blocks. Only one train may occupy a stretch of authority (which may consist of a single block or a stretch of dozens) at any given time, unless movements are to be made at restricted speed. Like TWC, DTC may be combined with ABS in high-traffic areas to aid with train separation and safety.

[edit] Form D Control

Form D Control System, or DCS, is a system similar to Track Warrant Control that is used by railroads subscribing to NORAC (Track Warrant Control is a GCOR term). The name comes from the form that train crews copy the authority on. A sample Form D is available here; line two is used to grant authority for occupying the track.

[edit] Centralized Traffic Control

Many large or heavily-trafficked railways use Centralized Traffic Control, or CTC. In CTC, train dispatchers (called "control operators" on larger railroads) monitor the location of trains electronically using track circuits, direct traffic by controlling the indication of absolute signals, and efficiently arrange oncoming train meets by automatically lining electronically-operated ("dual controlled") switches to cause trains to enter sidings. In addition to absolute signals controlled by the dispatcher, CTC territory usually includes intermediate signals between the absolute signals that operate similarly to ABS signals. These signals help keep trains separated between absolute signals, which can often be dozens of miles apart.

Because of the electronics used (the signals, the electronic switches, and the communications infrastructure), CTC track is much more expensive to build and maintain than track used in other methods of operation. In other methods of operation, train crews must stop to line switches when entering a siding (and may often be required to line them back when the entire train has left the main track, causing members of the train crew to walk long distances, unless otherwise authorized by the train dispatcher). CTC also enhances safety, as it allows train dispatchers to monitor the movement of trains to ensure they do not overrun their authority and provides for detecting the condition of the track.

In the western United States, railroads have built large sections of multiple main track, but they are operated under CTC instead of Rule 251. This allows the dispatcher greater flexibility in managing traffic by having some trains "cross over" to the other main track to pass slower or stopped trains or allow access by trains moving in both directions to spurs and industries on both sides of the track. In some extremely high-density corridors, there may be three or even more CTC-controlled tracks in parallel.

[edit] Signaling enhancements

Automatic Cab Signaling, or ACS, is often used as an overlay for ABS, Rule 251 and CTC. This system provides train crews with information about the next signal indication, even if the signal mast is not visible. Automatic Train Stop, or ATS, systems provide wayside inductors that, when activated, signal the train to apply its brakes. Automatic Train Control, or ATC, adds in-cab enforcement to these and will apply the brakes if a dangerous situation arises, such as when the next signal is displaying a stop indication but the engineer has not begun slowing the train. ATC is required on all U.S. rail lines that operate at more than 79 miles per hour.

A further enhancement designed to work in both signaled and dark territory is Positive Train Control, or PTC. This system is an overlay on the conventional methods of operation but also uses satellite-based tracking and computerized radio communication to verify the authority given to the train, current location of the train, the status of the next signal (if any), the position of switches (which will be equipped with a sensor and radio transmitter), and the location of any oncoming trains. As in ATC, if a dangerous situation arises, the system will apply the brakes.^[7][8][9]

[edit] References

1. ^ Compliance with Railroad Operating Rules and Corporate Culture Influences - Results of a Focus Group and Structured Interviews; U.S. Department of Transportation; Federal Railroad Administration; October, 1999
2. ^ Train accidents refers only to on-track equipment and trains. It does not include any data with motor vehicle collisions with trains.
3. ^ Derailment is defined in the Accident/Incident Bulletin as “A derailment occurs when one or more than one unit of rolling stock equipment leaves the rails during train operations for a cause other than collision, explosion, or fire.” Collision is defined in the FRA Guide to Accident Reporting as “an impact between on-track equipment consists while both are on rails and where one of the consists is operating under train movement rules or is subject to the protection afforded to trains.”
4. ^ A recent accident on BNSF near Fort Worth, Texas, on 1997-08-20, demonstrated this concern and resulted in the issuance of an FRA Safety Advisory which made several recommendations on securing unattended rolling equipment to reduce the inherent risks.
5. ^ Although not specifically defined in the Code of Federal Regulations, efficiency test is a commonly used term among railroad operating personnel. Essentially, efficiency testing refers to how railroad management conducts operational tests and inspections to comply with those portions of the federal regulation which require railroads to monitor operational performance and general compliance with operating rules (See 49 CFR 217.9: Programs of Operational Tests and Inspections; Recordkeeping).
6. ^ "NORAC: Northeast Operating Rules Advisory Committee: A common rulebook for a diverse Northeast" by Martin Graetz, Trains May 1, 2006, retrieved August 16, 2006
7. ^ Positive Train Control: Intelligent Railroad Systems, Federal Railroad Administration, retrieved August 16, 2006
8. ^ Most Wanted List of Transportation Safety Improvements, National Transportation Safety Board, retrieved August 16, 2006
9. ^ BNSF starts positive train control trial - North American Viewpoint, by William Vantuono, International Railway Journal, March, 2004, retrieved August 16, 2006