Chapter
AMERICAN RAILWAY ENGINEERING AND
MAINTENANCE OF WAY ASSOCIATION
Practical Guide to Railway Engineering
RailwayIndustry
Overview
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AREMA COMMITTEE 24 – EDUCATION & TRAINING
Railway Industry Overview
Paul Li, P Eng.
UMA Engineering, LTD.
Edmonton, AB. T5S 1G3
pli@umagroup.com
Maxwell B. Mitchell, P.E.
Norfolk Southern Railway (Retired)
Trion, GA 30753-1703
mbmitchell@att.net
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Chapter
Railway Industry
Overview
2.1 Introduction
T
he railway industry encompasses not only the operating railway companies
and transit authorities, but also the various government regulatory agencies,
railway associations, professional organizations, manufacturers and suppliers
of locomotives, railcars, maintenance work equipment and track materials,
consultants, contractors, educational institutes and, most important of all, the shipping
customers.
The information in this chapter is of a general nature and may be considered as typical
of the industry. However, each railway company is unique and as such it must be
understood what is included in this chapter may not be correct for a particular
company.
2.2 Railway Companies
Government owned freight railways are nowadays limited to some regional lines where
transportation service must be protected for the economic well being of the
communities. Passenger railways, on the other hand, are generally owned by
governments. Transcontinental services, such as the Amtrak or VIA Rail in Canada,
are corporations solely owned by the respective Federal Governments. These
passenger railway companies normally do not own the trackage infrastructures. Except
for certain connecting routes and dedicated high-speed corridors, they merely operate
the passenger equipment on existing tracks owned by freight railways. Local rapid
transit systems are usually operated as public utilities by the individual municipalities or
transit authorities on their own trackage. Commuter services may be operated by
government agencies or private sector on either their own or other railway owned
trackage.
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Freight railways in North America, including those owned by government, are usually
incorporated as separate legal entities from their owning shareholders. The major
railroads are usually owned by public companies with shares traded through the
various stock exchanges. Due to their age, most of these companies were incorporated
under special charters or acts of Congress. Private companies, the shares of which are
not openly traded, may own the smaller regional or short line railroads.
2.2.1 Organization of a Railway Company
An incorporated railway is governed through a Board of Directors appointed by the
shareholders at the Annual General Meetings (AGM) together with a public auditor.
The Board of Directors normally meets once a month to decide on corporate issues,
budget and major fund appropriation. Day-to-day business is handled by the Chief
Operating Officer (COO), Company Secretary, and Chief Financial Officer (CFO)
reporting to the Chief Executive Officer (CEO) who is the President of the company.
These four senior executives at the corporate level may be appointed by the Board of
Directors or shareholders at the AGM as stipulated in the corporate by-laws.
The COO heads the operation of the railway. Except for the Class 1 railways, the
CEO and COO are often one and the same person. Under the COO, there are four
major departments. These are the Transportation, Engineering, Mechanical, and
Marketing departments. There are other smaller yet important ancillary departments
under the COO that help run the company. These are the Human Resources,
Industrial Relations, Labor Relations, Safety and Loss Control, Occupational Health
Services, Supply Management (purchasing), Real Estate, Public Affairs and Police
Departments. The Corporate Affairs, Legal and Regulatory Affairs departments
usually report to the Company Secretary while the Financial Planning, Budget, Costing,
Accounting, Taxation, Internal Auditing and Information Technology (IT)
departments report to the CFO. The IT department’s reporting to the CFO is
possibly due to the history of computers being first introduced in railways for
accounting purposes. The Investor Relations department usually reports directly to the
CEO.
As the major railways’ networks span thousands of miles or even across the continent,
the operating departments (Transportation, Maintenance of Way and Structures,
Communications and Signals, and Mechanical) are normally structured in various levels
of geographic control. In the past, it was common to see four levels of management,
e.g. the Headquarters, Regions, Divisions and Subdivisions. Supervisors and managers
of the different operating departments reported upwards level-by-level, independent of
the other departments, to the three separate headquarter chiefs. There was no
marketing function in those days with all sales handled by the station agents reporting
through the Transportation Department.
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Modern communication facilities have allowed the railways to reduce the levels of
geographic control down to two or three. Some railways have changed their reporting
relation from the former line organization (single line up different department) to a
functional organization where the different operating departments within the same
geographic level report to one General Manager of Operations. The operating
departments of Transportation, Maintenance of Way and Structures, Communications
and Signals and Mechanical transform into functions within one “Operations
Department,” so to speak. These railroads believe that this type of organization
promotes cooperation among the operating departments and improves operations.
However, many railroads have retained the departmental line reporting structure as
outlined in the above paragraph. The departments of such railroads do work closely
with their counterparts in the other departments.
Transportation Department
The Transportation Department is responsible for train operations on lines and in
terminals as well as tracking the locations of all locomotives and rolling stock (loads
and empties). Terminal operation includes supervising of yard crews in the breaking
up of arrived trains, marshaling traffic into different destination blocks, and the making
up of departing trains. Line operation includes the supervision of Rail Traffic
Controllers (train dispatchers and tower operators) and train crews (locomotive
engineers, conductors and trainmen) to ensure on time delivery of trains. While the
yard and train crews report to the front line transportation supervisors and terminal
operations coordinators (trainmasters and yardmasters), crew calling for duty is done in
some railways through a Crew Management Center. The conductor is the head of the
train crew and responsible for the complete train while the locomotive engineer is
responsible for the operation of the locomotives and train handling. In the absence of
the conductor, the locomotive engineer is in charge of the train. In the past,
locomotive engineers reported to the master mechanics because of the specialized
trade knowledge required to operate the locomotives. Nowadays, locomotive
engineers report to the transportation supervisors. Passenger and Commuter/Transit
railways include a Passenger Operations Department to handle the logistics associated
with transporting people including train scheduling, information dissemination,
ticketing and stations, as well as the operations of large passenger terminals. Rail traffic
controllers (dispatchers) report through a separate line of supervisors in the Rail Traffic
Control Centers. With the advance of communication technology, many railways have
centralized their former local dispatching centers under one roof for the entire
network.
The traditional function of Traffic Systems in tracking locations of loads has been
replaced electronically by the universal Automatic Equipment Identification (AEI)
system adopted in North America. However, some car-checkers are still required to
assist the yardmaster in locating specific cars within major terminals.
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The chief of transportation at the headquarters level is now responsible only for
network operations, centralized rail traffic control, motive power control, car
management, traffic system service reliability, service design, Operating Practices (rules
and training) and network capacity planning.
Engineering Department
The Engineering Department is responsible for the maintenance and construction of
plant infrastructures, including track, roadbed, right-of-way, bridges, drainage culverts,
buildings, signal plant, communication systems and electric traction systems.
Much smaller crews covering larger territories now replace former sizable local
maintenance of way crews. Their work consists mainly of small day-to-day
maintenance repairs such as defective rail change out behind rail test cars, correcting
track geometry defects found by the Track Geometry Car, and emergency repairs
necessitated by adverse weather conditions and derailments. The track supervisors
(roadmasters) are responsible for track inspection and workforce management. Much
of the reporting is now commonly done in the field with a portable computer or using
the touch-tone pad of a telephone.
Large mechanized production crews that may travel over sizeable portions of the
railroad, for the most part, now perform programmed or out-of-face rail and tie
renewal work.
The Bridge and Building Group (B&B) is generally responsible for the track carrying
bridges, occasional overhead roadway bridges, under track culverts, and roadway signs.
In the past, the B&B forces also were responsible for the railway’s buildings, hence, the
building portion in the name. However, for the most part, contractors on many freight
railroads handle the building maintenance function. On many commuter and transit
properties, the Bridge and Building Department continues to be responsible for station
buildings and platform structures.
The Work Equipment Group maintains and performs heavy repairs for track and
bridge maintenance machines used by the Maintenance of Way and Structures
department as well as signal & communications and electrical traction equipment. This
group may even design and build machines that the supply industry does not offer the
industry.
Communications and Signals are responsible for maintaining the in-house telephone
and radio communications system, the active wayside train control signals, the railhighway grade crossing signals and dispatcher centers.
For electrically powered railways, the Electrical Traction department is also a separate
engineering function, which maintains the electric traction system including
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substations, electrical distribution system, power management systems and required
bonding and grounding.
The Engineering Services (Design and Construction) function looks after all the
technical services, such as liaison with regulatory agencies, surveying, design, drafting,
tendering and contract administration to facilitate construction work. They also handle
all applications for wire, pipe and road crossings, industrial private tracks and 3rd party
construction.
For those railroads where all departments report to a General Manager Operations, the
Chief Engineer at headquarters is primarily responsible for engineering standards,
research and development, maintenance practice, centralized design functions (track,
signals and communications systems, bridges and structures, etc.) and prioritizing the
maintenance and capital budget among division needs. For those railroads where the
departments report through their own departmental chain of command, the respective
headquarters Engineering Department Chief Engineer is responsible for the above
functions as well as the program maintenance functions, structure maintenance and
renewal, signal upgrades and installations, and track, bridge, culvert and signal
inspections.
Mechanical Department
The Mechanical (Motive Power and Equipment) Department at the division level is
responsible for scheduled maintenance, inspections and repair of locomotives and
rolling stock. Day-to-day maintenance of locomotives includes basic inspection,
fueling, sanding, changing brake shoes, flushing out toilets and washing. Minor repairs
to railcars include changing out wheels, air hoses and brake shoes. Major repairs to
locomotives and fleet conversion of railcars are now mostly done at the “back shops”
under headquarters’ control. With some railways, the car mechanics responsible for
inbound and outbound inspections of trains now report to the Transportation
Department. The Mechanical department may also be responsible for the majority of
the MOW rolling stock.
The Mechanical Chief is responsible for equipment standards, maintenance practices
for motive power and rolling stocks, and the major repair shops.
Marketing Department
The Marketing Department concentrates on research and development of various
market sectors (e.g., coal, sulphur, potash, fertilizer, grain, agricultural products, metal
and minerals, timber, pulp and paper, automotive, merchandising and intermodal) and
revenue growth. The Industrial Development group handles the negotiations with
customers in the construction of private trackage. The other functions of Marketing
include customer services, account management, quality assurance and operation
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interface. With some railways, operations of the intermodal terminals and cargo flow
also report to the Marketing Department.
2.3 Regulatory Agencies and
Railway Associations
2.3.1 Regulatory Agencies
United States
The Surface Transportation Board (STB) regulates railroads regarding mergers in the
United States. Additionally, the STB has the power to issue directed service orders to
one railroad to operate another, or a portion of another railroad that is no longer
capable of operating on its own. Such operations normally continue until such time as
either an acquisition is made or it is determined to discontinue service all together. In
the early 1980's, railroads were deregulated in the rate-making arena and Federal
approval is not required for the raising or lowering of rates. Railroads may now enter
into rate contracts with customers.
In the operations area, the Federal Railroad Administration (FRA), a part of the
Department of Transportation, regulates the railway industry. Among the things that
the FRA regulates are locomotive and rolling stock inspections and brake tests, train
operating procedures, radio communications procedures, track and signal safety
standards, fall protection, as well as employee on-track safety. Additionally, the
Occupational Safety and Health Administration (OSHA) regulates work place safety of
railroads in areas that the FRA does not have specific regulations unless the FRA has
made a determination that regulations are not needed in that specific area.
Additionally, in the United States, the National Transportation Safety Board (NTSB) is
charged with investigating all major train accidents and the issuance of cause findings
as well as recommendations for the prevention of future occurrences. The NTSB’s
recommendations are not binding unless the FRA adopts them. However, with very
few exceptions, even if the FRA does not adopt the recommendations, the company
on which the train accident occurred will adopt the NTSB’s recommendations in at
least some modified form.
Other governmental authorities exerting regulatory control over the railways include
state agencies, state Departments of Transportation (DOT), commerce commissions
and local governmental entities empowered to enact local ordinances.
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Canada
In Canada, the Canadian Transportation Agency (CTA), Transport Canada (TC), and
the Transportation Safety Board (TSB) regulate the Federally Regulated Railways, the
railways that are inter-provincial. Intra-provincial railroads are provincially regulated.
The CTA addresses rate disputes, switching disputes, cost appropriations disputes
(fencing, installation of crossing warning systems, etc.). They listen to both sides,
consult with Transport Canada, and make determinations within sixty days of hearing
the dispute.
TC regulates railroads at the federal level in a similar manner as the FRA does in the
United States except for on-track safety or fall protection. While the regulations in the
two countries are not identical, they are similar. On-track safety and fall protection are
regulated by Labour Canada. Transport Canada requires that affected railways adopt
and comply with the AREMA Communications and Signals Manual of Recommended
Practice recommendations.
TSB, similar to the NTSB in the United States, investigates serious train accidents.
Recommendations of the TSB are reviewed and sometimes worked into existing rules
or operating practices.
Many provinces adopt some or most of the Federal regulations/rules regarding the
intra-provincial railroads. Other provinces have completely separate regulations for
railroads under their jurisdiction.
2.3.2 Railroad Associations
There are numerous railway associations that address the various functional areas of
the railway industry.
AAR and RAC
The Association of American Railroads (AAR) is the industry lobbying association of
the major freight railroads in United States, Canada and Mexico, as well as Amtrak.
The AAR, working closely with Congressional and government leaders, helps
formulate the framework of railroad operations in North America. It fosters
cooperation among railways and helps set operating rules, regulations on the handling
of inter-line traffic and interchange standards for railway equipment. The Railway
Association of Canada (RAC), with 55 freight, passenger, commuter and tourist railway
members, is the counterpart of AAR in Canada. For more information on AAR and
RAC, visit www.aar.org and www.railcan.ca.
The AAR also provides railroad information exchange services through RAILINC,
one of its two subsidiaries. Transportation Technology Center, Inc. (TTCI) is the
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other AAR subsidiary. With its 48 miles of test track in Pueblo, CO, TTCI focuses on
research programs that will enhance railroad safety, reliability and productivity.
AREMA
The American Railway Engineering and Maintenance-of-Way Association (AREMA)
is the organization that represents the engineering function of the North American
railroads. This organization was the result of the merger in 1997 of the American
Railway Engineering Association (AREA), the American Railway Bridge and Building
Association, and the Roadmasters and Maintenance of Way Association. In 1998, the
Communications and Signals group that had been a part of the Association of
American Railroads (AAR) joined AREMA, thus bringing all of the engineering
functions under a single umbrella. The AREMA mission is centered about the
development and advancement of both technical and practical knowledge and
recommended practices pertaining to the design, construction and maintenance of
railway infrastructure. One of the primary tasks of the 26 committees making up
AREMA is the development and updating of the recommended practices provided in
the AREMA Manual for Railway Engineering.
For more information, visit
www.arema.org.
REMSA
On the supply side is the Railway Engineering-Maintenance Suppliers Association
(REMSA). This association consists of many of the vendors that supply the products
and services that the railway engineering departments need. REMSA was created in
1965 by the merger of the Association of Track and Structures Suppliers and the
National Railway Appliances Association. The association represents companies and
individuals who manufacture or sell maintenance-of-way equipment, products, and
services, or are engineers, contractors and consultants working in construction and/or
maintenance of railway transportation facilities. The mission of REMSA is to provide
global business development opportunities to members; to transfer knowledge about
markets, products and the industry to members and their customers, and to support
government initiatives that advance the North American railroad industry. For more
information, visit www.remsa.org.
RSSI
Railway Systems Suppliers, Inc. (RSSI) is a trade association serving the
communication and signal segment of the rail transportation industry. RSSI continues
to grow with over 250 member companies. The primary effort of RSSI each year is to
organize and manage a trade show for its member companies to exhibit their products
and services. The association was incorporated in 1966 as the Railway Signal and
Communication Suppliers Association Inc. Previous to that time it existed as two
separate entities, one for the signal area and one dealing in the communications area of
the railroad industry. Although records are vague for the years previous to 1966, there
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are indications that one or both of these entities were in existence as far back as 1906.
In 1972 the corporate name was changed to Railway Systems Suppliers, Inc. The
governing body of the RSSI is made up of fourteen directors from fourteen member
companies and meets five times a year. For more information, visit www.rssi.org.
2.4 Operations of Railways
2.4.1 Safety First in Railway Operations
The safety of operations, being the safety of employees and train operations, is the first
priority of railroads. No one should be exposed to unnecessary hazards and risks.
Responsibility for safety cannot be transferred. Each employee and contractor of a
railroad must accept this principal and each is personally held accountable for his
actions. Safety is a condition of working on a railroad.
Railway transportation entails the movement of heavy equipment carrying people and
goods, some of which can be hazardous or even flammable. An accident inflicts not
only property damage but also personal injuries, occasionally fatal. Where long
stretches of track are destroyed by a derailment, it may take days to restore traffic.
The business of railways has been deregulated by governments, but not the safety of
operations. On issues regarding safety of operations, although the railways are
provided with the opportunity to self-regulate, they remain reportable to the FRA or
Transport Canada. Except for minor incidents involving no personal injury, property
damage or hazardous material release, all accidents must be reported to regulating
agencies. These regulating agencies have authority to issue temporary speed
restrictions or even suspend operations until the investigation is completed and the
cause of the accident determined.
The investors and customers are also concerned about the railways’ safety records.
Wall Street analysts include the railway’s safety performance in their evaluation of the
company’s value. Potential customers, particularly those in the petroleum and
chemical industries, commonly evaluate accident records of the railways on the
proposed routes before choosing a carrier. The business success of a railway depends
greatly on its safety performance.
The Safety and Loss Control Department of a railway is generally set up as a function
independent of line operations but often reporting directly to the COO. This set-up is
to ensure that safety is never compromised by economy of operations. The Safety and
Loss Control Department provides safety training, performs safety audits, makes
recommendations for safety improvement, keeps records of all accidents, and ensures
investigations are done impartially. However, unless safety is ingrained in each and
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every employee, no Safety Department can make a railway safe. The safety process
must be ingrained in all departments from the department head down to each and
every employee as well as contractor/consultant employee with all employees taking
responsibility and accountability for safety.
2.4.2 Bibles of the Railways for Safe Operations
In order to achieve the capacity to move the required amount of traffic safely and
productively under all weather conditions, every railway must have certain “bibles” to
regulate its operations. These are:
§
The Operating Rules, which are generally adopted from either:
§
The General Code of Operating Rules (GCOR) by the Association of
American Railways (ARR), or
§
The Canadian Rail Operating Rules (CROR) by the Railway Association of
Canada,
§
The NORAC Operating Rules used by some New England & Eastern United
States Railways,
§
Norfolk Southern Operating Rules,
§
CSX Operating Rules,
§
The General Operating Instructions (GOI),
§
Current Timetable and Terminal Operating Manuals, including special
instructions and subdivision instructions,
§
General Bulletin Orders (GBO) and Daily Operating Bulletins (DOB).
Each railway requires its operating employees to be re-trained and re-qualified at
regular intervals ranging from one year in the United States to one to three years in
Canada.
Railway Engineering Departments, the Federal Railroad Administration (FRA) in the
United States and Transport Canada in Canada issue additional instructions that
regulate how maintenance and construction of the components that make up the
physical elements of the railway structure are to be maintained and/or performed,
including but not limited to:
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MOW Rules or Chief Engineers Instructions/Standard Practice Circulars
(SPC’s).
§
FRA Track Safety Standards.
§
Transport Canada Track Safety Rules.
§
FRA Rules and Regulations Governing Railroad Signal and Train Control
Systems.
§
FRA Fall Protection (Workplace Safety).
§
FRA On-Track Safety (Workplace Safety).
The AREMA Manual for Railway Engineering, the AREMA Portfolio of Trackwork
Plans and the AREMA Communications & Signals Manual of Recommended
Practices provide industry recommended practices associated with design, construction
and maintenance of railway track, bridges, signal and communication systems,
roadway, roadway related facilities and electric traction systems.
2.4.3 Tracks and Authority of Movements
Tracks are divided into “main tracks” and “other than main tracks” based on the level
of control required for train or engine movements.
The main track is the track extending through yards and between stations, upon which
trains or engine are authorized and governed by one or more methods of control. The
main track must not be occupied without authority or protection. The term
“mainline” is not defined in the rulebooks and generally refers to the series of
subdivisions on which most of the traffic is carried, as opposed to secondary lines and
branch lines.
Portions of the main track may be designated by limit signs in the field and/or by
timetable or special instructions that permit certain types of movements without
specific authority. Certain speed restrictions normally apply. These limits are often
called “Yard Limits”.
Occupancy of “Other Than Main Tracks” does not require authority from a
dispatcher/rail traffic controller (RTC) or tower operator. This class of tracks includes
all tracks other than the main tracks or sidings. Safety of movement on these tracks
depends on the locomotive engineer looking out for other movements, obstructions,
and people working on the tracks. The Rule Book therefore requires that trains or
engines on “Other Than Main Tracks” must move at a speed that allows them to stop
within half the range of vision short of train, engine, or railroad equipment fouling the
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track, stop signal or derail or switch lined improperly or a maximum of 20 MPH,
whichever is less (Restricted Speed).
There is one other type of track, Sidings and Signaled Tracks, that can either be
controlled under main track rules or “other than main track” rules. A siding is defined
as “a track auxiliary to the main track, for meeting or passing trains, which is so
designated in the timetable.” General bulletin orders (GBOs), train orders, or daily
operating bulletins (DOBs) and track bulletins are instructions regarding track
condition restrictions and other information which affect the safety and movement of
a train or engine. Signaled siding and signaled tracks, on which main track rules apply,
are usually listed in the subdivision instructions of timetables. Note that signaled
sidings or tracks refer to those tracks where the entire trackage is bonded with track
circuits and signaled, not just the turnouts.
In the United States, trackage may be designated as “FRA Excepted Track” by the
owner. This trackage is exempt from the FRA Track Safety Standards with the
exception of maintenance of required track inspection frequencies and maximum
permissible gage. The maximum permissible speed operated on these tracks must not
exceed 10 mph. The operation of revenue passenger trains or freight trains with more
than 5 placarded cars (hazardous material) is not allowed. (See Chapter 3 Basic Track –
Track Geometry for more information and requirements associated with Excepted
Track.)
2.4.4 Speeds
Speed is a vital yet conflicting factor in the transportation business. Higher speeds
improve capacity and productivity but increase the safety risk and maintenance costs.
Each railway goes through strenuous analysis to establish the maximum permissible
speeds on its network of main tracks to balance the effect of safety and maintenance
costs against capacity and productivity. Compliance to the speed restrictions is
mandatory to the well-being, of not only the company, but also its operating
employees.
The maximum permissible speeds or zone speeds on main tracks are shown in the
subdivision instructions in the timetable. Separate speeds are usually specified for
passenger, freight, and express trains. Different speeds may also be allowed for
opposing train directions and tracks.
Within a speed zone or designated subdivision, there are usually temporary speed
restrictions (TSR) and permanent speed restrictions (PSR). PSR are listed in the
timetable with the maximum permissible speeds operated over the subdivision and
may have signs along the track, dependent upon the carrier. TSR are usually
designated by bulletins.
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At locations where main tracks are connected with turnouts or intersecting each other
with diamond crossings (railroad crossings at grade), movements usually have to slow
down to a speed that can be safely accommodated by the turnouts or crossings. On
non-signaled tracks, the speed restrictions are listed as PSR in the timetable. On
signaled tracks, the signals are designed to indicate the maximum permissible speed of
the movement through the turnouts and interlocking. Unlike the traffic lights on city
streets, railway signal systems are capable of displaying dozens of different instructions
to the trains through various combinations (up to a hundred for some railways) of
color lights, relative positions of the lights, and use of marker plates. These different
signal aspects are designed to provide speed instructions, not only for that particular
signal location, but also for the second or even third signal further down the track.
Operable speeds over track are also defined by the FRA Track Safety Standards in the
United States and the Transport Canada Track Safety Rules. Speeds are defined by the
Class of Track (Class 1 through 5) and High Speed (Class 6 through 9) in the United
States and Classes 1 through 6 in Canada. Permissible operating speeds are limited by
performance criteria in a number of track oriented parameters. (See Chapter 3 – Basic
Track, Track Geometry for more detail.)
2.4.5 Rail Traffic Control Systems
Before any communication device was available, train movements were by fleet
operations, that is, all trains ran in one direction until all had arrived, then they operated
in the opposite direction. Next came operations by timetable schedules, which allowed
trains to operate in both directions. Trains were classified by superiority to determine
which train would take the siding at a meet. The lower class train had to wait at the
siding until the higher class train had arrived or its schedule became ineffective after 12
hours. With the installation of telegraph lines, a system of train dispatching by
“timetable and train orders” was rapidly adopted due to its ability to handle nonscheduled or “extra” trains. The train order process is safe but time consuming. In
order to achieve higher capacity, railways have evolved into more efficient traffic
control systems, with or without signal control.
Most of the former train order rules have been eliminated and replaced with
occupancy control system (OCS) rules in the CROR (Canada), or with track warrant
control (TWC) or direct traffic control (DTC) rules in the GCOR (US). These
modern non-signaled systems are modified train order systems that take advantage of
the high-tech radio communication and computers.
Radio Communication of Train Orders
A train order, clearance, authority or instruction that is required to be in writing can be
transmitted by voice radio communication from the dispatcher/operator or in Canada,
the rail traffic controller (RTC), to the train and copied in writing by a member of the
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train crew, usually on a pre-printed form. The crew member copying the order must
repeat the order to the dispatcher/operator or RTC, word for word from the copy.
The dispatcher/operator or RTC checks the repeat against his/her written order for
correctness, underscoring each word and digit as it is repeated. If correct, the
dispatcher/operator or RTC will respond complete, the time and the initials of the
dispatcher/operator or RTC, which are recorded by the crew member. The order is
not complete and must not be acted upon until the crew member has acknowledged
by repeating the complete time and the initials of the dispatcher/operator or RTC to
the dispatcher/operator or RTC and an OK is given by the dispatcher or RTC.
Train Spacing and Block Separation
When trains were dispatched by timetable and train orders, a train following another in
the same direction relied on time spacing and flag protection to prevent rear-end
collisions. A train was not allowed to depart a station less than five or ten minutes,
depending on the road, after a preceding train in non-signaled territories had departed.
If a train slowed down, the flagman in the caboose had to light and throw off five or
ten-minute fusees to signal the following train to immediately reduce speed to
restricted speed. If the train stopped, the flagman had to scramble back a sufficient
distance to protect the train.
Rear-end collision can be prevented by dividing the track into “blocks” and allowing
only one train in each block at a time. The early Manual Block Signal (MBS) system
had operators stationed at each block entrance to manually set the block signals to
indicate whether the block was occupied or not. The early signals consisted of a black
ball hoisted on a pole, with the high position indicating “proceed,” hence the term
“high ball.” This later evolved into the use of “semaphore” arms and to the current
color lights that can be set by dispatchers hundreds of miles away.
The automatic block signal (ABS) system was developed after Dr. William Robinson
invented the track circuit in 1872. The ABS system is mainly used for directional
operations on two or more tracks with designated current of traffic or on relatively
low-density single tracks.
Track Circuit
Insulated joints are used to separate the track circuit of each block from another. A
battery powered low voltage direct current is passed through the two rails from one
end of a block to energize a relay at the other end of the block. The energized relay
coil picks up the iron relay armature to close the “proceed” signal circuit, which is
powered by another battery. When the track is occupied, the wheels shunt the track
circuit, taking current away from the relay. With the relay coil not energized, the
armature drops by gravitational force (no spring used in railway relays) and opens the
“proceed” signal circuit to give a “stop” indication. The track circuit is a fail safe
design and is often referred to as the Vital Circuit. If any of the components fail, such
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as a rail break, the circuit drops to indicate a “stop” signal. This is the basic one-block
signal plant. Current systems are more sophisticated, using complicated interlocked
switching logic to provide multi-block indications.
Signal Block Length
The single block system is not practical as all trains, not knowing whether the next
block is occupied or not, must slow down such that they are prepared to stop at the
end of each block. The current ABS systems use “two-block, three-indication” as a
minimum standard. With the two-block, three indication system, each block must be
at least as long as the longest normal stopping distance for any train on the route,
travelling at its maximum authorized speed. When a block is occupied, the signal into
this block automatically drops to a “stop” or “restricting” indication, allowing a
following train to proceed only at restricted speed. (On some roads, this may be a
“stop and proceed” indication requiring a train to stop before being permitted to
proceed at restricted speed.) The signal into the block immediately following the
occupied block changes to an “approach” indication when the block is vacated. An
“approach,” allows a following train to proceed into this first vacant block but requires
it to slow down preparing to stop at the next signal. The signal into the second vacant
block (i.e., if both blocks are not occupied) would give an unrestricted “clear”
indication, allowing a train to proceed at track speed. In order to move trains along
smoothly without slowing down due to receiving an approach indication, the trains
must be spaced two blocks or two braking-distances apart. The excess train spacing is
one braking distance.
To increase line capacity, more and more railways are changing to a three-block, fourindication system by dividing the existing block lengths into halves. The fourindication system requires the use of an additional secondary approach signal indication
such as an “advance approach,” which indicates to be prepared to stop at the second
signal ahead. The three-block separation, each block being only half the braking
distance, allows trains to be spaced at one and one-half the braking distance apart.
The purpose of automatic block signals is to prevent rear-end collision. The ABS
system is best suited for double or multi track territories with designated “current of
traffic,” normally running on the right-hand track. Passing of a slow train by another
train in the same direction is impossible by ABS alone. When passing is needed, or
when track work or serious delay requires left-hand movements against the current of
traffic, clearances (train orders) are issued. Nowadays, any remaining ABS systems are
mostly operated within OCS or TWC rules.
Centralized Traffic Control
On single track territories or double track sections where crossing over is allowed,
there is no current of traffic. The common signaled system used in such a territory is
the centralized traffic control (CTC) system. The requirement for an absolute “stop”
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(instead of the permissive “stop and proceed”) and wait for train meets or passes
necessitate the use of “controlled signals” at sidings, junctions or crossovers in double
track sections. These controlled signals and the associated switches are lined and
locked by dispatchers remotely located in a centralized rail traffic control (RTC) center
often hundreds of miles away.
All turnouts within a CTC territory are circuit controlled and interlocked with other
track circuits. Turnouts at controlled locations (sidings, junctions and crossovers) are
often equipped with “dual control switches.” A dual control switch is normally power
operated remotely by the dispatchers and electrically locked, but can be released by a
qualified employee for manual operation in the field. Other turnouts (to industrial
spurs, private tracks or some low traffic branch lines) between controlled signals are
normally hand operated and equipped with either an “electric lock” (old regulations) or
a standard key lock.
Authority to enter a CTC main track (or re-enter after having cleared one) at a
controlled location is by signal indication. The train crew (engineer or conductor)
requests permission verbally by radio communication with the dispatcher. After
ensuring that there is no conflicting movement, the dispatcher lines the switch and sets
the signals (remotely) to authorize the train to proceed. For entry through an
electrically locked switch between signals, the dispatcher gives permission to the train.
Controls for a CTC section of track are located on a panel (or recently on a computer
screen) at the dispatcher’s desk with a diagram of the trackage and lights (or indicators)
showing the locations of all trains. The dispatcher makes plans for train movements
and sends his instructions to the interlocking plants at the ends of each siding by
turning a knob, pushing a button, or the use of a computer keyboard. Control of the
signals and switches in an extended territory over only two line wires (or recently by
microwave) was made possible with pulse-code technology developed in the 1930’s.
These are the “non-vital” circuits that can use up-to-date electronics to speed up,
simplify and reduce the cost of transmitting information. The vital-circuit relays in the
field control and interlock switches, signals and track circuits to ensure safety of
movements. When the switch points are lined or the signals have cleared, a message is
sent back from the field location to the dispatcher console to confirm that the action is
complete.
In between sidings, opposing train movements are not possible on the single track, but
following movements in the same direction are allowed. The single track between two
sidings usually includes absolute permissive block (APB) circuits that function with
intermediate block signals between the sidings. These circuits can determine the
direction of a train and drop all opposing signals from one siding to the next to red as
soon as the train heads out onto the single track. The circuits also allow signals behind
the train to clear as it moves from block to block, allowing following train movements.
Most major railways have installed “intermediate signals” between sidings or controlled
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signals to facilitate fleeting of trains. Spacing of intermediate signals has the same
effect on line capacity as previously discussed for ABS.
Single track with CTC is considered to have about 70% of the capacity of ABS doubletrack. With longer trains and heavier loading in recent years, many railways are
trimming their excess capacity by converting most of their ABS double-track to singletrack CTC with long sidings and high-speed turnouts for better asset utilization and
improved flexibility in handling train speed differential.
Additional Information
For further information about timetables and signal systems, see Chapter 7 of this
Practical Guide to Railway Engineering [or Chapter 7 of The Railroad What It Is, What It
Does, by John Armstrong].
2.5 Railway Cars
2.5.1 Freight Cars
Most freight cars are configured as a car body (to carry the freight) sitting on two
trucks, each with two axles. A pair of steel wheels is semi-permanently attached to a
steel axle with the wheel flanges installed on the gauge side and the wheel tread on the
field sides. A set of roller bearings (or journal box in older railcars) is bolted to each
end of the wheel-axle, which the truck frame straddles. The truck frame consists of
two side frames connected by a bolster beam. Two or three coil springs between the
bolster and the side frame serve to dampen the shock during motion. Brake rigging
under the truck frame connects the brakes to the brake cylinder. At the center of the
bolster, there is a cast integral truck center plate and a center pin. The car body sits on
each center plate and is connected to the center plate by the pin. Two roller bearings
and housings on each side of the bolster serve to facilitate and limit the swivel of the
truck allowing the railcar to negotiate through curves.
As freight cars are interchanged from railway to railway throughout the continent, they
may require repair at any time or location. All replacement parts for the undercarriage,
including the wheel/truck assembly, brake system, and drawbar/coupler assembly, are
standardized with few variations. This eliminates the necessity for each railway to
maintain an enormous inventory of replacement parts and work force “know how” to
repair the different types of cars from different owners. Furthermore, these parts are
designed for easy removal and replacement to minimize delays to traffic enroute. This
standardization is promoted by the AAR.
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Although the basic configuration of the freight railcars never changed over years, the
car bodies have evolved considerably according to the specific requirement for the
different commodities carried.
Boxcars
The old boxcar, as the name implies, is a plain wooden box on wheels to protect the
lading (cargo) from the weather. A sliding door on each side facilitates loading and
unloading of goods. Newer boxcars are made of steel in various lengths with doors of
larger sizes or types to allow access by forklifts. Some are equipped with interior
bulkheads to restrain loads. Boxcars are the general vehicles for carrying packaged
goods that require protection from rain or snow. The most common types of goods
carried are pulp and paper, plywood and OSB boards, packaged non-perishable food
products and consumer merchandise.
Insulated Boxcars and Mechanical Reefers
Insulated boxcars are used for short haul of perishable produce. For longer haul,
refrigerator cars (commonly known as reefers) are used. These are insulated steel
boxcars with a mechanical refrigeration device to control the temperature.
Intermodal Cars – Piggyback Trailers and Containers
Consumer goods and food produce are normally shipped from the manufacturers and
producers on rail in boxcars over long distances to major distribution centers. From
there, these goods are trans-loaded onto highway trucks for final delivery to the shops
or retailers. With the development of tractor-trailers, most of these goods are now
loaded straight into trailers. To realize the economy of long haul by rail, these trailers
are lifted onto flat deck railcars in an intermodal terminal near the origin and shipped
by express trains to another intermodal terminal near the distribution centers. This
type of intermodal traffic is generally known as trailers on flat cars (TOFC).
A recent development in rail transportation of trailers is to eliminate the use of railcars.
The specially equipped trailers are positioned on special bogies on the track and
coupled together. As this type of train is much lighter than the normal intermodal
trains, specialized smaller motive power units can be used. This type of service has
become so reliable that some carriers operate them over long distances of 1,000 or
more miles.
With much ocean freight now switched to the use of containers, import and export
merchandise is carried in standard 20 foot or 40 foot long containers. On the
highways, these containers are carried on flat deck trailers. On rails, these containers
are loaded onto flat cars. This is termed containers on flat cars (COFC) intermodal
traffic. Double-stacking of these containers on specialized intermodal flatcars allows
shipping of two or four containers on one platform. A loaded double-stack car is over
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20 feet tall above top of rail and is significantly taller than the standard 15-foot height
of most railcars. More and more domestic merchandise is now also shipped in
domestic containers, which are longer than the ocean freight containers.
Double-stacked intermodal trains have become one of the most important parts of
railway business. This is the fastest growing traffic despite severe competition with
highway trucks. Except for the pulp, paper and lumber boards, most boxcar traffic has
now been replaced by the TOFC or COFC traffic. Some of the trailers or containers
are also equipped with a mechanical refrigerating device for temperature control like
the reefers. Intermodal flatcars are often coupled permanently in packs of 2, 3, 4 or 5
platforms. Some multi-pack intermodal platforms are articulately connected with bogy
trucks, i.e., two platforms sharing the same railway truck.
Flat Cars
Flat cars are one of the earliest types of railcars and used for carrying commodities with
lengthy dimensions such as timber logs, cut lumber, pipes and other long finished
metal products. The easy accessibility also makes flatcars an ideal carrier for
construction equipment, machinery and any dimensional loads.
General service flat cars usually have a wood deck to facilitate nailed-down anchorage
for loads. Other flat cars are specially modified for carrying certain types of goods, such
as the built-in center beam and bulkhead ends for carrying lumber and wood products.
TOFC and COFC are other modifications to flat cars.
Auto Rack Cars
Another modification to the flat car is the development of bi-level and tri-level carriers
for finished automobiles. These auto rack cars carry 12 to 18 automobiles each,
making it economical to transport finished autos for long distances at low rates. The
auto racks are now fully enclosed to minimize damage and vandalism.
Gondola Cars
Another common type of railcar is the gondola car. These are open metal wagons on
wheels to facilitate top loading. Some gondola cars are equipped with removable
covers to protect the cargo from rain and snow. To prevent contamination of the
environment by the fine dust, soft covers or spray coatings may be used. The early
gondola wagons were five to six feet deep. As the strength of drawbars and couplers
increased, the gondola wagons increased in height to carry more tonnage per car. The
shallow gondola cars are normally used for heavy commodities such as rocks, metal
products and metal scraps. The tall gondolas are used for carrying loose bulk
commodities such as coal, sulphur, potash, grain, plastic pellets, woodchips and
sawdust. Most tall gondolas used for carrying these loose bulk commodities are built
or modified as hopper cars.
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Hopper Cars
Hopper cars are gondola cars built with hopper doors at the bottom to facilitate gravity
off-loading. The interior side walls of most hopper cars are sloped (in individual
compartments) to funnel the contents through the hopper doors. Some covered
hoppers, such as those carrying grain or cement, may be cylindrically shaped with
smaller openings on the top for loading.
Rotary Gondola/Hopper Cars
For certain commodities, portable devices may be used to shake or vibrate the hopper
cars to promote faster off-loading. Some gondola and hopper cars are equipped with
rotary couplers so that the whole railcar may be rotated on its side to shake the lading
off the top.
Tank Cars
Tank cars are cylindrical in shape. Commodities carried are usually in a liquid state,
such as petroleum and chemicals, including liquefied petroleum (LP) gases and molten
sulphur. As the contents carried in tank cars are usually hazardous or under high
pressure to maintain its liquid state, the design and construction of these cars is
stringently controlled. Some are built to maintain structural integrity to prevent leakage
even after derailment. Handling and switching procedures, including the relative
position of these cars in a train, are strictly regulated. Switching of certain loaded tank
cars over the hump yard is not allowed.
Maintenance-of-Way Cars
The typical maintenance-of-way department will posses a number of specialty cars for
purposes of performing maintenance and construction related work. These cars
include air-dumps for side depositing of fill material and rip-rap for bank stabilization,
ballast hoppers for depositing controlled amounts of ballast through a variety of
controlled bottom dump doors, idler flat cars for rail cranes, Continuous Welded Rail
trains for unloading or loading of CWR, specialized trailer or camp cars for housing
large production gangs, wire cars for installation of overhead catenary wire in electrified
territory, conventional gondola cars for hauling rail and ties and box cars for specialty
mobile storage of materials.
Schnabel Cars
Schnabel cars are designed to carry large,
heavy loads. These cars separate into two
parts with the load becoming an integral part
of the car, as it is attached back together for
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shipment. The car illustrated is just a small version of the many types of Schnabel cars
that have been built.
2.5.2 Hazardous Commodities
Government regulations require that all railcars carrying hazardous or dangerous
commodities display a placard indicating the type of content carried or previously
carried (residual in empties). Movements of these cars on a train must also be
accompanied with documentation for emergency cleanup instructions. If the
document for a certain car is missing, the train can only move at restricted speed to the
next nearest location where the car can be set out.
2.5.3 Passenger Cars
Unlike freight cars, passenger cars are designed and built for the safe and comfortable
carriage of people. The interior of passenger cars is usually specially laid out as
coaches, sleepers, dining cars, sightseeing domes and baggage cars. Passenger cars in
urban transit systems are designed to accommodate both sitting and standing
passengers to achieve maximum capacity.
Over the years, there has been much improvement to passenger cars. The most
significant improvements are in the body structure and under-carriage in the
suspension system. New passenger cars are designed to remain upright after
derailment and have stringent crash worthiness requirements. Some cars are designed
with a suspension mechanism to automatically tilt the car on curves so that the
passenger train may be operated at a higher speed than normally acceptable to older
equipment.
The fastest presently operating passenger train is the French TGV at approximately
200 mph. The Japanese bullet train and the Swedish tilt train operate at about 120
mph. Scientists are developing new propulsion systems, such as magnetic levitation, to
raise the speeds of passenger trains to a higher plateau.
2.6 Locomotives
In North America, all steam locomotives of the old railroad age were long ago replaced
with diesel or electric locomotives, except for a few tour trains. Unlike the steam
locomotive, the mechanical energy developed by the diesel engine is used to generate
electrical power to drive the traction motors at the driving axles and the air compressor
to maintain the air-brake system. The proper term should actually be diesel-electric
locomotives. Electric locomotives do not have the diesel engines and draw electrical
energy directly from the overhead power distribution system or a third rail at the track
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level. (See Chapter 9, Railway Electrification.) Unlike in Europe, use of electric
locomotives in North America is almost exclusively for urban transit. Practically all
freight railways in America use diesel-electric locomotives.
There are different makes and models of diesel-electric locomotives in various sizes
and shapes. Those used in passenger services are more streamlined in shape for highspeed operations. Dual mode locomotives are utilized on some passenger and
commuter railways. These locomotives have the capability of operating as a straight
electric locomotive in electrified territory or as a straight diesel locomotive where the
overhead electrical propulsive system is not available. The most important factors in
classifying locomotives are:
§
Horse-power of the engines,
§
Maximum tractive effort developed,
§
Weight of the locomotives,
§
Running gear ratio, and
§
Number of driving axles.
Trains require little energy to move the goods over level distance, but significantly
more energy to move uphill (or braking energy downhill) even on the gentlest grade.
At 15 mph, the extra energy required to lift a train to an elevation 200 feet higher,
would move the same train about 21 miles at the same speed if it were on level track.
Grade is highly significant for a heavy train. A train powered at 1.5 hp per ton, which
could make 60 mph on level track, will slow to about 22 mph on a 1% grade and to 10
mph on a 2% grade. The same train will eventually stall, as the grade gets steeper.
Railways actually seldom use much more than 0.5 hp per ton to move their heavy
trains.
2.6.1 Horsepower (hp) and Tractive Effort
Horsepower is a measure of the rate of doing work. One horsepower = 550 ft-lbs. per
second or 375 lb-miles per hour. At zero speed, horsepower is also zero. The rated
maximum horsepower of most diesel engines is developed between 800 and 1000 rpm.
The available crankshaft hp is converted (by a generator, alternator or rectifier) to
electricity. After using part of the gross hp to power the cooling fans, blowers, air
brake compressor, etc., the remaining horsepower drives the wheel axles via the
traction motors. With the modern diesel electric locomotives, normally 82% of the
diesel horsepower is available for traction.
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The tractive effort (in pounds) available from a locomotive can be roughly calculated
as:
Tractive Effort (lbs.) = Horsepower X (308)
Speed (mph)
Where 308 is 82% of 375 lb-miles per hour per hp. For example, a 3000 hp
locomotive will have approximately 74,000 lbs. tractive effort at 12.5 mph.
2.6.2 Tractive Force and Adhesion
It is the tractive force at the locomotive driving wheels (drivers) at the rail that starts
and moves tonnage up various grades. The maximum tractive force that can be
developed at the rail is equal to the weight on drivers multiplied by the adhesion
(coefficient of friction) of the wheels on the rail.
The primary factors, among others, affecting adhesion are rail condition and speed.
Adhesion decreases as speed increases. At about 10 mph, adhesion varies from less
than 10% on slimy, wet rail to about 40% on dry, sanded rail. In general, with the aid
of the sanders, approximately 25% adhesion is usually available.
As all the wheels on most diesel locomotives are driving wheels, the weight of the
locomotives must be about four times the tractive force developed. The HHP (high
horsepower) units for main line service weigh about 195 tons each on 6 axles. The
maximum tractive force is therefore approximately 97,000 lb. per locomotive or 16,000
lb. per axle; that is, if there is enough horsepower at the wheel rims to develop the
tractive effort.
2.6.3 Drawbar Pull
After some of the tractive effort is used to move the locomotive itself, the remaining
effort, in the form of “drawbar pull,” is used to move the rest of the train. As the train
speed increases, the tractive effort from the locomotives decreases and the drawbar
pull available to move the train also decreases.
Due to the limited strength of drawbars and coupler knuckles, the number of
locomotives or motorized axles that can be used in the head end of a train is restricted.
Although rated with a minimum strength of 350,000 lb. (general service coupler made
of Grade B steel), coupler knuckle failure may happen at 250,000 lb. due to age and
wear. Grade E knuckles used on some captive services may have an ultimate strength
of 650,000 lb.
To avoid the risk of drawbar failure enroute, it is recommended to limit the number of
motorized axles in a locomotive consist to 18 (three 6-axle units). If more tractive
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effort is required to move the tonnage of a train, the option of in-train motive power
should be considered.
2.6.4 Train Resistance
Train resistance, the force required to move a train, is the sum of the rolling resistance
on tangent level track, grade resistance and curve resistance of the locomotives and
cars. Other resistances due to wind velocity, tunnels or different train marshalling will
not be discussed here.
Rolling Resistance
Rolling Resistance is the sum of the forces that must be overcome by the tractive effort
of the locomotive to move a railway vehicle on level tangent track in still air at a
constant speed. These resistive forces include:
§
Rolling friction between wheels and rail that depends mainly on the quality of
track.
§
Bearing resistance, which varies with the weight on each axle and, at low speed,
the type, design and lubrication of the bearing.
§
Train dynamic forces that include the effects of friction and impact between
the wheel flanges against the gauge side of the rail and those due to sway,
concussion, buff and slack-action. The rail-flange forces vary with speed and
quality of the wheel tread and rail, as well as the tracking effect of the trucks.
§
Air resistance that varies directly with the cross-sectional area, length and shape
of the vehicle and the square of its speed.
In general, rolling resistance of a train, R (in lb.), can be calculated using an empirical
expression as follows:
R = A + B V + C D V2
where A, B, C & D are coefficients defining the different resistive forces that are either
independent, dependent or affected by the square of the train speed V.
Davis Formula
The first empirical formula to compute rolling resistance was developed by W.L. Davis
in 1926. The original Davis formula provided satisfactory results for older equipment
with journal bearings within the speed range between 5 and 40 mph. Roller bearings,
increased dimensions, heavier loadings, higher train speeds and changes to track
structure have made it necessary to modify the coefficients proposed by Davis. Since
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then, there had been various modifications. Interested readers may refer to Section 2.1
of Chapter 16 in the AREMA Manual for Railway Engineering for more information.
Starting Resistance
The resistance caused by friction within a railway vehicle’s wheel bearings can be
significantly higher at starting than when the vehicle is moving. Depending on the type
of bearings, weight per axle and the temperature of the bearing, starting resistance can
range from 5 to 50 lb/ton. The ambient temperature and the duration of the stop as
shown below affect temperature of the bearing.
Type of Bearings
Above Freezing
Below Freezing
Journal Bearing
25 lb/ton
35 lb/ton
Roller Bearing
5 lb/ton
15 lb/ton
Starting resistance is generally not much of a problem with the very large tractive effort
available with modern diesel locomotives, except on steeper grades. If necessary, the
locomotive engineer can bunch up the train first, then start the train one car at a time.
The cars already moving will help start the ones to the rear. This is called “taking
slack” to start.
Grade Resistance
Grade Resistance is the force required to overcome gradient and is equal to 20 lb. per
ton per percent grade. This force is derived from the resolution of force vectors and is
independent of train speed. An up grade produces a resistive force while a down grade
produces an accelerating (negative resistive) force. A train moving up a long tangent of
1% grade at 10 mph, a speed that most tonnage trains slow down to at ruling grade
locations, will have a train resistance coefficient of 22.4 to 23.5 lb. per ton with the
grade resistance accounted for over 85% of the total.
Curve Resistance
Curve Resistance is an estimate of the added resistance a locomotive or car must
overcome when operating through a horizontal curve. The exact details of the
mechanics contributing to curve resistance are not easy to define. It is generally
accepted in the railway industry that curve resistance is approximately the same as a
0.04% up grade per degree of curvature (which equals 0.8 lb. per ton per degree of
curvature) for standard gauge tracks. At very slow speeds, say 1 or 2 mph, the curve
resistance is closer to 1.0 lb. (or 0.05% up grade) per ton per degree of curve.
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2.6.5 Compensated Grade
It is a common practice to describe curvature and grade together as compensated
grade. Compensated grade is the algebraic total of the track gradient and the
equivalent grade of the curve.
Gc = G + Dc * 0.04
Where Gc =
compensated grade in %
G = track gradient in %
Dc =
degree of curvature in decimal number
The track gradient “G” is positive for up grade and negative for down grade. The
equivalent grade of a curve is always positive; i.e., at +0.04% per degree of curve with
tangent tracks as 0.00%. The combined resistance due to track geometry can thus be
calculated by converting the compensated grade at 20 lb. per ton per percent grade as
shown below.
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Track
Gradient
Degree of
Curvature
Compensated
Grade
Grade and Curve
Resistance
+ 0.44 %
3û 45’
+ 0.59 %
+ 11.8 lb/ton
+ 0.50 %
Tangent
+ 0.50 %
+ 10.0 lb/ton
- 0.73 %
Tangent
- 0.73 %
- 14.6 lb/ton
- 0.73 %
4û 30’
- 0.55 %
- 11.0 lb/ton
Note that curves on down grades help reduce the accelerating force of coal trains
coming down from the mines. In railway operations, keeping a train under control
over a long stretch of steep down grade poses a much bigger problem than powering
the same train uphill.
2.6.6 Acceleration and Balance Speed
It takes about 100 lb. force to accelerate a mass of 1 ton at the rate of 1 mph per
second. The total tractive force, "F" (lb.), required to accelerate a train of "W" tons
(locomotive and cars) at the rate of "A" mph per sec. can thus be calculated
approximately as:
F (lb.) = 100 W (ton) A (mph/sec)
After a portion of the drawbar pull is used to overcome the train resistance, the excess
is used to accelerate the train. Rolling resistance for a train increases as the speed
increases. At the same time, the tractive effort of the locomotive (and thus the
drawbar force) decreases as the speed increases. As the available drawbar force
decreases, the accelerating rate drops. For a train operating on a long stretch of
consistent grade, there is an equilibrium point when the total drawbar pull is equal to
the total train resistance. At this point or speed, the train will accelerate no more. This
is the “balance speed” (or balancing speed) of the particular train on that particular
grade.
If the grade resistance increases after the balance speed is reached, the train will slow
down to another balance speed for the increased grade. If the grade keeps on
increasing, the train will slow to a speed that the locomotive cannot sustain and will
stall.
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At any given speed that the train is to maintain, there is a maximum tonnage that a
locomotive can pull up a specified grade. This is the tonnage rating of the locomotive
for the specified grade.
2.6.7 Tonnage Ratings of Locomotives
Most railways publish “Tonnage Ratings” for their locomotive fleet. These ratings
indicate the maximum tonnage that a specific locomotive can haul over a given
territory at a specified minimum speed.
Obviously, no single rating can be used for assigning maximum tonnage where the
number of cars (axles) and their weights vary from train to train. A system has been
developed and used on most railways, which makes it possible to express tonnage
ratings without regard to the weight of the cars in a train.
2.6.8 Ruling Grade
On any particular section of railway, the ruling grade (compensated) determines how
much tonnage can be hauled. This is the particular point on the section at which the
combined grade and curve resistance makes the train pull hardest and, therefore, rules
how much tonnage can be hauled by a locomotive consist. It is not at the same
location for both directions, and may not be the same location for all trains.
2.6.9 Momentum Grade
The ruling grade may not be the steepest grade on the section. A short grade does not
affect the whole train length at the same time. A short incline may be run as a
momentum grade, if conditions are such that trains can get a good run for the hill. If
the velocity head of the train at the foot of the grade is higher than the actual rise, the
incline is a momentum grade. Velocity head, h in feet, can be calculated as:
h (ft) = v2 / ( 2 g )
&
where v =
g=
train speed in ft/sec at foot of grade,
gravitational acceleration, or
h (ft) = 0.03 V2
where V =
train speed in mph at foot of grade
Conversely, if the velocity head, h, is less than the actual rise in feet, the grade is
considered as a ruling grade. The effects of train length must be considered in the
above calculation to ensure a good portion of the train is over the hill when the
velocity head is depleted.
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2.6.10 Power to Stop
In moving traffic over a railway, power to stop can be more important than tractive
force, bigger cars or stronger couplers. In order to maximize the capacity of the
existing line, trains are run as close as possible (with minimum headway) at reasonable
speed without running into each other. That takes reliable braking power.
The air brake used in railway cars is a fail-safe, reversed action system. Plainly
described, the brakes on each car are released when the brake pipe pressure is charged
up and maintained (80 to 90 psi for most freight train operations) throughout the train
by the air compressors on the locomotives (or from a yard air plant prior to departure).
The train brakes are actuated by a controlled reduction (minimum 10 psi reduction to
avoid sticking brakes on release) of the brake pipe pressure. This reduction causes the
valve on each car to release air from the auxiliary reservoir (charged up at the same
time as the train line) to build up pressure in the brake cylinder, applying the brakes.
Each pound of reduction in brake pipe pressure will build up approximately 2.5 psi
pressure in the brake cylinder. At 85 psi brake pipe pressure, a full service reduction of
25 psi will produce approximately 60 psi in the brake cylinder. At this point, the
pressures in the reservoir and cylinder are equal, and any further reduction will have no
further effect.
There is a second “emergency” reservoir on each car. With an emergency application,
the brake valve opens the brake pipe wide. The resulting rapid rate of brake pipe
pressure reduction causes the car valves to dump the air of both auxiliary and
emergency reservoirs into the brake cylinder. The resulting brake cylinder pressure is
approximately 20% higher than that of a full service application. The rate of
application back through the train is as fast as 900 ft. per second.
The braking power is dissipated as heat at the brake shoes and wheels. On long steep
grades, it is necessary to release the brakes intermittently or stop the train to cool the
wheels. Increasing or recharging the brake pipe pressure from the locomotives releases
brakes. Increasing the brake pipe pressure will cause the brake valve to completely
exhaust the brake cylinders and recharge the reservoirs. As it takes time to recharge
the system, the train is momentarily without brakes after a full service application or
series of smaller reductions.
Although the locomotives have independent brakes (straight air system used mainly for
controlling slack and during switching operations) and some locomotives are equipped
with dynamic brakes, to prevent jack-knifing, most of the braking force has to be from
the train brakes. In mountainous territory, keeping the heavy trains under control
should be the key concern in grade designs.
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2.7 Traffic Systems
The railway business is the business of transporting people and goods. The
transportation of people (the most precious commodity of all) requires the highest
standards for safety, comfort and speed. Passenger trains are always operated as
scheduled trains with the highest priority at the fastest speed that is safe for the track
conditions and type of passenger equipment used. Operations of passenger trains
ideally are within minutes of the schedules.
On time delivery of freight trains is also vital to the success of a railway, particularly for
high value commodities and traffic extremely competitive with highway trucks. In
order to keep inventory cost low, customers dealing in high value commodities, such as
the automotive industry, normally keep minimum inventory to meet demands or
production schedules. They do not tolerate late delivery by more than a few hours.
Merchandise and intermodal traffic are highly competitive with other modes of
transportation. The railways must handle this traffic with high priority in order to
remain in the market place. Intermodal and automotive trains are operated as core
scheduled express trains. These trains are designed to bypass as many terminals as
possible and provided with enough horsepower to operate at the maximum allowed
speeds. On time delivery must be achieved within a couple hours of the schedules.
Bulk commodities such as coal, sulphur and grain are normally shipped in unit trains
with no switching between origins and destinations. In exchange for economy of
freight rates, the shippers normally will tolerate some delay except when the trains have
to make a direct connection for a certain ship at the seaport. These heavy tonnage
trains seldom achieve track speed on uphill grades. Bulk trains are usually operated on
an as-required basis using available track time windows between core trains. Schedules
for these trains are usually zero based; i.e., the clock starts ticking when the train
departs at the origin.
Manifest trains handling all other commodities are operated as quasi-core scheduled
trains. Schedules for these trains are normally planned 48 to 72 hours ahead based on
traffic availability by the Network Operations Control and confirmed 24 hours prior to
departures. Traffic on these trains normally requires switching at intermediate
terminals for train connections. The railways usually have a certain amount of
flexibility in handling this traffic and a delay of up to 12 hours may be acceptable.
Wayfreights or road switchers are the work trains that spot and switch traffic for
customers along the line and within terminals. The labor cost to operate a switcher on
a main line subdivision is usually the highest among all trains. While through trains
may be operated with a reduced crew (engineer and conductor), road switchers require
a full crew (1 or 2 additional trainmen) to line switches and derails, apply and release
handbrakes, perform walking inspection of cars and air-brake system and to protect
pushing movements. The simple “hook and haul” activities of a road switcher, picking
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up (say 5) loads and re-spotting empties at an industry on a line with sidings 20 minutes
apart, will take approximately an hour of the main track time.
The window required for on-line switching significantly impacts the capacity of the
main track to handle through trains. When a road switcher occupies the main track
while picking up or spotting loads/empties at an industry, all through freights are
delayed from running through the block. In most cases, the dispatcher may choose to
delay and hold the road switcher at the nearest siding until there is an adequate window
for the switcher to complete its work and clear the block. On a medium traffic line
handling 20 through freights per day, the average delay to a switcher waiting at a siding
for the one-hour window is approximately 45 minutes to an hour. The total switcher
time to serve this industry is therefore 1.75 to 2 hours.
The duration that a train crew may work on a one-way trip is usually limited by
government regulations or collective labor agreement to 12 hours. After deducting 2.5
hours at the initial terminal for making up the train in the order that cars will be
switched, 3 hours road time and another half hour to tie-up at the final terminal, there
is usually not much time left for actual switching and waiting for work windows.
2.7.1 Priority of Trains
Based on market demand, railways prioritize the dispatching of their trains as follows:
§
Passenger trains
Priority 1
§
Express intermodal and auto trains
Priority 2
§
Manifest trains
Priority 3
§
Wayfreight and road switchers
Priority 3
§
Bulk trains contracted for specific delivery intervals
Priority 3
§
Other bulk unit trains
Priority 4
Other railroads may prioritize their trains differently.
On double track territories, where each track is signaled for traffic in one direction
only, trains operate according to designated current of traffic, except during track
outage or work blocks. In this situation, trains do not have to stop for meets. If all
trains running in the same direction operate at the same speed, they do not have to
stop for passes either. Unfortunately, trains do operate at different speeds by design to
meet the market requirements. On single track territories, which make up the majority
of the North American network, trains have to stop and wait for meets and passes.
In the decision as to which train will take the siding and wait for a meet or pass, the
first factor considered by the train dispatcher is usually the priority of the trains.
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Consider the situation where a double-stack intermodal train is closely followed (say 2
blocks apart) by a higher speed passenger train and has to meet a slow moving heavy
bulk train between sidings A and B. If all these trains are on schedule, the likely
decision by the train dispatcher would be to put both the intermodal train and the bulk
train in the two sidings and let the passenger train pass. The intermodal train would be
the next one cleared onto the main track, while the bulk train remains delayed in the
siding until both other trains have gone by. The dispatcher’s decision may vary if the
passenger train is ahead of schedule or if the computer’s “meet-pass planner routine”
advises that such decision would introduce significant delays to other trains in the
territory beyond acceptable limits.
The railways usually have three different maximum allowed speeds specified for the
same class of track, with the fastest speed for passenger trains, the middle one for
express trains and the slowest speed for all other freight trains. If all trains on a
segment of track are operated at the same speed, higher speeds will allow more trains
to move through the segment. Train delays at sidings for meets are inherent and
unavoidable with single-track territories. The amount of total train delays between two
sidings is related to the running time between the sidings, the efficiency of the signal
system and the number of trains operated per day. Train delays at sidings to let other
trains pass are caused by speed differentials between trains in the same direction. The
greater the speed differential between trains, the more trains that will be delayed “in the
hole” to let the high-speed train by. Speed differential in the same direction, therefore,
introduces more train delays and reduces the capacity of the line segment.
2.7.2 Effects of Sharing Tracks by Freight and
Passenger Trains vs. Track of Single Use
There is a physical limit as to how many trains could be put through a segment of
single track, depending on the siding grid time, signal system and dispatching
efficiency. If one “channel” of the available capacity is required for each normal
through freight, it is generally believed that a conventional passenger train will need 2
channels, while an express train requires 1.5 channels. A passenger train takes up to 2
channels of the available capacity only if it is running at 3-inch unbalance (regarding
curve elevation) over the normal freights. If the passenger train uses specialty
equipment and operates at speeds significantly higher than the freight trains, it will take
up more capacity from the line. It may therefore be advantageous to operate highspeed passenger trains on dedicated tracks when there are enough trains to justify the
infrastructure investment. There are also other safety advantages to operating
passenger trains on dedicated tracks. The heavy long freight trains, particularly the
bulk trains, kick the track out of line and surface a lot faster than the light passenger
trains. The out-of-surface track does not affect the slow moving freights as much as
the fast passenger trains. If a track is jointly used by freights with passenger trains, the
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safety and comfort level required for the passengers will necessitate more frequent
track re-surfacing than if the track is used for freight alone.
2.7.3 Overcoming the Delays that Occur in Freight
Yards
Freight Yards are necessary in the railway business in order to originate, transport and
terminate shipments of freight. However, they can be real handicaps in that they
inherently cause delays to freight in transit, thereby upsetting shippers. Railways often
spend large sums of money both to construct efficient, high-speed main tracks and to
get trains over the road as rapidly as practicable. But when these trains
arrive
in
terminals, the cars they brought may sit idle awaiting switching and departure to their
destinations.
In order to eliminate such delays, railways will often "mainline" trains at intermediate
terminals rather than "yard" them there. In this process, locomotives are fueled and
serviced on a main track, or on a track immediately adjacent thereto. Air brake tests
can also be made there if required. Engine and train crews are changed at the same
location, thereby minimizing a yard's effects on a train while taking advantage of its
service capabilities and personnel.
If a train does not require fueling and servicing, crews are sometimes changed at a
siding outlying a terminal, with personnel being transported by van or carryall. Then
the train, with its new crew, simply "runs" the terminal as if it did not exist, saving
many hours or even days of delay.
When a train is run essentially intact over more than one railway, then the same
locomotive consist is often run through on all of the railways. This requires the ability
to change the frequencies of onboard radio equipment to match those of the railroads
being operated on. Preserving the continuity of a train (and its air brake line) reduces
the number of required air brake tests, also saving time. Intermodal trains usually travel
from and to facilities specifically constructed to handle truck trailers and containers. At
these facilities, the switching of trailers and containers (on chassis) is handled on the
pavement by hostler or dray tractors. This rapid handling makes this service
competitive with straight truck transport.
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