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APPENDIX 2
Glossary of Shared-Track Definitions
Abandonment
Abandonment and discontinuance of railroad service is allowed by federal law, which permits
a carrier to end its obligation to provide common carrier service over a particular rail line. Aban-
donment procedures are set forth in 49 CFR 1152. The procedures for abandonment or discon-
tinuance of a rail line are complex and they establish rigid time limits. Railroads therefore some-
times mothball a branch line without formally abandoning it.
Centralized Traffic Control (CTC)
A centralized traffic control system is a method of train dispatching that emphasizes the
remote operations of the interlocking plants from a central control center. Typical features of a
CTC installation includes: (1) remotely controlled, interlocked switches; (2) track occupancy
indicator lights on mimic boards located in the control center; (3) traffic controls that enable
specific track sections to be designated for a direction of traffic; (4) automatic wayside signals
that behave in concert with the traffic control settings; and (5) full bidirectional operations on
all tracks under rules similar to NORAC Rule 261.
Class I Railroad
The Surface Transportation Board defines a Class I railroad as a railroad carrier whose operat-
ing revenue exceeds $277.7 million (in 2004). Class I railroads generally operate freight trains on
the general system of railroads. There are currently seven Class I railroads in the United States:
CSX Transportation, Norfolk Southern Railway, BNSF Railway, Union Pacific Railroad, Kansas
City Southern Railway, and the U.S. portions of Canadian National Railway and Canadian Pacific
Railway.
Commingled Operations
Commingling between light transit and conventional vehicles implies that trains operating
over a shared-track segment are separated from one another on purely track warrants, signal
indications, automated train control systems, or other such like train signaling systems. FRA
stipulations require a system that ensures "fail-safe train separation" between light transit and
conventional railroad trains. On a commingled system, both light transit and conventional
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Glossary of Shared-Track Definitions 89
equipment are dispatched in the same manner, with no operational distinction made for the
train or equipment type. It does not mean that light transit and conventional equipment is oper-
ated in the same train consist.
Crash Energy Management (CEM)
A method structural design that controls structural crush by analyzing the dynamic crush
behavior of the vehicle, relating it to passenger safety incorporating features into the railcar struc-
ture to absorb and dissipate collision energy in a manageable and predictable fashion to minimize
injury to passengers and crews. Also referred to as collision force management and controlled
crush design.
Diesel Multiple Unit (DMU)
A diesel multiple unit is a passenger railcar that has a number of special features: (1) Onboard
(typically underfloor) propulsion equipment that enables it to move under its own power with-
out a locomotive; (2) Multiple unit capability, which allows two or more DMUs to be coupled
together and simultaneously operated by a single operator as a train; and (3) Typically has driv-
ing cabs at both ends allowing the DMU to reverse direction without a loop or wye track facility.
For the purpose of FRA Regulations, a DMU is classified as a locomotive.
FRA-Compliant
This refers to the requirements in CFR 49 Part 238 for 800,000 lb sill end compressive force
resistance (buff strength) and other specified strength requirements, including anti-climbing,
forward facing end structures, collision posts, corner posts, rollover strength, and side structures.
See Non-FRA-Compliant.
FRA Waiver
For any entity to operate non-FRA-compliant equipment on track that is connected to the
general system of railroads, exceptional permission must be sought from the FRA by petition.
The FRA will publish a notice in the Federal Register, solicit public comments, and conduct
analyses. At the end of the regulatory process, the FRA will publish a Letter of Decision. Typi-
cally, the letter of decision grants certain relief from specified parts of Title 49 of the CFR. FRA
commonly will impose certain conditions or limit the scope of a specific element of a peti-
tioner's request. This Letter is sometimes referred to as the FRA Waiver. The Waiver gives the
entity legal authority to operate in the specified manner, subject to the conditions outlined in
the Waiver.
Fringe Period
Fringe periods are the periods near the beginning and end of the transit and railroad service
days, typically between 11 p.m. and 1 a.m., and between 4 a.m. and 6 a.m. This is sometimes
termed the shoulder of the service day.
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90 Shared Use of Railroad Infrastructure with Noncompliant Public Transit Rail Vehicles: A Practitioner's Guide
General System of Railroads
General railroad system of transportation means the network of track over which goods may
be transported throughout the nation and passengers may travel between cities and within met-
ropolitan and suburban areas, and portions of the network that lack a physical connection may
still be part of the system by virtue of the nature of the operations.
Grandfathering
An operating practice is said to be grandfathered if it predates a legal requirement that out-
laws the practice, but is allowed to continue on an exception basis.
Haulage Rights
A "guest" railroad has haulage rights over another if it has the legal authority to require the host
railroad to transport the guest's traffic over the host's lines, using any means deemed appropriate
by the host railroad.
Light Passenger Rail Cars
Light rail passenger vehicles, a generic term applied to all passenger vehicles that do not com-
ply with 49 CFR Part 238 Subpart C Specific Requirements for Tier I Passenger Equipment. See
Non-FRA-Compliant.
Limited Nighttime Joint Operation
The scripted temporal separation arrangement on the San Diego Trolley is termed "limited
nighttime joint operation" in the original petition submitted by SDTI and in the corresponding
FRA letter of decision.
Non-FRA-Compliant
This refers to rolling stock used on the general system of rail transportation that does not com-
ply with the structural requirements of 49 CFR Part 238.
Northeast Operating Rules Advisory
Committee (NORAC)
NORAC is a voluntary association of railroads that maintains a common set of operating rules
for the Northeastern United States. The main members include: Amtrak, Conrail, NJ Transit,
SEPTA, Providence & Worcester, New York Susquehanna & Western, and a number of smaller
railroads. Other railroads that incorporate elements of NORAC Rules within their own rule-
books include Guilford Rail Systems, CSX Transportation, and Norfolk Southern.
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Glossary of Shared-Track Definitions 91
Operations Control Center (OCC)
An operations control center supervises train operations over a railroad or light rail territory.
Typically light rail controllers or conventional railroad dispatchers are stationed in the OCC. The
OCC often has track occupancy indicators, radios, phones, and other tools designed to monitor
operations and ensure the safe and orderly movement of traffic. A CTC installation is not nec-
essary for an OCC, but an OCC is a prerequisite for a CTC installation.
Scripted Temporal Separation
Light transit operations are under scripted temporal separation if there is a script governing
the transfer process, allowing more operationally complex modes of sharing the segments of the
shared-track system. This script is approved by the FRA in a Waiver Petition, and may only be
modified with the permission of the FRA. The script may entail joint operation of conventional
and light rail equipment in opposite directions, in double track territory. See the San Diego Trol-
ley case study in text.
Shared Corridor Operations
Use of a rail corridor by various types of equipment including freight and passenger. It is assumed
to include FRA-compliant rolling stock, technology and practices and non-FRA-compliant rolling
stock, technology and practices. Parallel operation of any or all types of equipment on adjacent
tracks is implied but shared use of the same track is excluded (since that is defined by shared
track). See Spatial Separation.
Shared-Track
In shared-track operations, light rail vehicles operate on the same tracks used by conventional
trains. FRA has written policy governing this type of operation, in which fail-safe train separa-
tion between light transit and conventional railroad trains is required. The term "shared use" is
occasionally used when "shared-track" is meant.
Shared-Track Operations
Use of a track on the general system of rail transportation by various types of equipment
including freight and passenger, assumed to include FRA-compliant rolling stock, technology,
and practices and as well as rolling stock that lacks the required buff strength, technology and
practices. Commingled operation of any or all types of equipment on the same track is implied.
At this time, temporal separation is the only acceptable technique currently in use and
approved by FRA for a number of specialized transit operations in the United States. Therefore,
there are no true shared-track operations at present. The FRA/FTA Joint policy statement ("Pro-
posed Joint Statement of Agency Policy Concerning Shared Use of the General Railroad System
by Conventional Railroads and Light Rail Transit Systems," 64 Federal Register; 28238; May 25,
1999) gives some guidance for the consideration of a positive train separation system as a possi-
ble alternative to temporal separation. This policy is now codified in 49 CFR Part 211.
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92 Shared Use of Railroad Infrastructure with Noncompliant Public Transit Rail Vehicles: A Practitioner's Guide
Spatial Separation
Light transit agencies are considered spatially separated from the general system of railroads
if the two operations do not share track. Diamond crossings are not considered spatially sepa-
rated and special FRA regulations apply. See Shared Corridor Operations.
Split Point Derails
A split point derail is a specially designed railroad turnout that allows either a straight ahead
movement or a derailing movement that directs the train into a runaway ramp. It is sometimes
called a catch point. It offers better protection than a mechanical derail, which is a small metal
wedge that sits on top of one rail.
Standard Operating Procedure (SOP)
Standard Operating Procedure is a document typically issued by a light rail operating agency
that governs light rail employees in addition to the rulebook. It is typically used to cover special
operating conditions. The equivalent document on a mainline railroad is generally a special
instruction. It is termed a special order on some East Coast light rail systems. In the case of San
Diego Trolley, the SOP forms a script that describes a number of operating scenarios. The SOP
is a critically important element of each petition submitted to the FRA.
Temporal Separation
Light transit operations are considered temporally separated from the general system of rail-
roads, if the two share track, but may only operate on the shared segment within predefined and
fixed time windows. The track is shared by freight and light rail, and each mode is allocated a
separate and individual operating period. Occupancy of the track is typically transferred between
the light rail and the railroad operations once daily. See Shared-Track Operations.
Trackage Rights
A guest railroad has trackage rights over another's tracks (the host railroad) if it has the legal
authority to operate trains over the host's property, while following the host's rules and under
the supervision of the host's dispatcher.
Transfer Procedures
Transfer procedures refer to the mechanisms employed to ensure that vehicles entering the
shared-track territory are safely regulated and controlled. For temporally separated operations
in the United States, the shared track enters freight mode when all light rail operations have
ceased, the shared-track is verified as vacant by the dispatcher, and a predefined transfer proce-
dure is carried out to change operations to freight mode.
