10100100010000111010100011101010001000101011001110110101001010100010100110010100010001
11101010100010001110100100100001000111101010010001101100111011010100101010001010011001
010001000111101011000010001110100100100001000111101010010001000011101010001110101000101
110101
DEVELOPING 0
TECHNOLOGY:01010100010100110010100010001111010101000100011101001001
PTC
00001000111101010010001010110011101101010010101000101001100101000100011110101100001000
11101001001000010001111010100100010000111010100011101010001000101011001110110101001010
10001010011001010001000111101010100010001110100100100001000111101010010001101100111011
0101001010100010100110010100010001111010110000100011101001001000010001111010100100010
00011101010001110101000100010101100111011010100101010001010011001010001000111101010100
01000111010010010000100011110101001000100001110101000111010100010001010110011101101010
01010100010100110010100010001111010101000100011101001001000010001111010100100010000111
01010001110101000100010101100111011010100101010001010011001010001000111101010100010001
11010010010000100011110101001000100001110101000111010100010001010110011101101010010101
00010100110010100010001111010101000100011101001001000010001111010100100010000111010100
01110101000100010101100111011010100101010001010011001010001000111101010100010001110100
10010000100011110101001000100001110101000111010100010001010110011101101010010101000101
00110010100010001111010101000100011101001001000010001111010100100010000111010100011101
01000100010101100111011010100101010001010011001010001000111101010100010001110100100100
00100011110101001000100001110101000111010100010001000001110101000111010100010001010110
01110110101001010100010100110010100010001111010101000100011101001001000010001111010100
10001000011101010001110101000100010101100111011010100101010001010011001010001000111101
01010001000111010010010000100011110101001000100001110101000111010100010001010110011101
10101001010100010100110010100010001111010101000100011101001001000010001111010100100010
Positive train control in the
00011101010001110101000100010101100111011010100101010001010011001010001000111101010100
01000111010010010000100011110101001000100001110101000111010100010001010110011101101010
Northeast Corridor came
01010100010100110010100010001111010101000100011101001001000010001111010100100010000111
01010001110101000100010101100111011010100101010001010011001010001000111101010100010001
before the rest of the industry
11010010010000100011110101001000100001110101000111010100010001010110011101101010010101
00010100110010100010001111010110000100011101001010000010001111010100100010000111010100
by Al DiCenso
01110101000100010101100111011010100101010001010011001010001000111101010100010001110100
10010000100011110101001000110110011101101010010101000101001100101000100011110101100001
00011101001001000010001111010100100010000111010100011101010001000101011001110110101001
hile the nation’s freight railroads
01010001010011001010001000111101010100010001110100100100001000111101010010001010110011
scramble to put positive train con10110101001010100010100110010100010001111010110000100011101001001000010001111010100100
trol in place by the end of 2015,
01000011101010001110101000100010101100111011010100101010001010011001010001000111101010
Amtrak has used a crash avoid10001000111010010010000100011110101001000110110011101101010010101000101001100101000100
ance system on parts of the busy and fast
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00111011010100101010001010011001010001000111101010100010001110100100100001000111101010
Northeast Corridor since 1999. Amtrak
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put the first segment of its Advanced Civil
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Speed Enforcement System, or Acses
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(pronounced “AX-es”), into operation
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along the Boston to New Haven, Conn.,
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segment as part of its electrification and
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modernization program. Acses prepared
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11101001001000010001111010100100010000111010100011101010001000101011001110110101001010
the route for America’s new fast trains, the
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sleek Acela Express. On this and two oth00111010100010001000001110101000111010100010001010110011101101010010101000101001100101
er stretches of the Northeast Corridor, the
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system guards all trains moving at speeds
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of up to 150 mph. Predecessors of the sys10101001000100001110101000111010100010001010110011101101010010101000101001100101000100
tem have been used for more than 90
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00111011010100101010001010011001010001000111101010100010001110100100100001000111101010
years, beginning in the 1920s when the
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Pennsylvania Railroad developed its fourA southbound Acela races across a stretch of positive
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aspect cab signal system. The system kept
train control trackage on Amtrak’s Northeast Corridor at
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the
engineer
informed
of
conditions
Perryville, Md., on June 5, 2011. Michael T. Burkhar t
00001110101000111010100010001010110011101101010010101000101001100101000100011110101100
00100011101001010000010001111010100100010000111010100011101010001000101011001110110101
00101010001010011001010001000111101010100010001110100100100001000111101010010001101100
AHEAD
OF THE
REST
W
IN THE CAB
ahead, even in rain, snow, and fog. The system became increasingly sophisticated in
the 1950s with speed control development,
which not only required the engineer to acknowledge a signal commanding him to
slow, but also brought the train to a stop if
he did not respond.
Track improvements for high-speed
Metroliners in 1969 underscored the need
for a system that would enforce speed restrictions for bridges, curves, and congested areas, as well as temporary speed restrictions in work zones. Fatal wrecks on
the corridor heightened the need for such a
system, including the infamous 1987 crash
at Chase, Md., in which a set of light Conrail units and Amtrak’s Colonial passenger
train collided. In that tragedy, drug-influenced engineer Ricky Gates ran a stop signal and struck the Amtrak train, killing 16.
Another incident, less severe, took place in
1990, when a student engineer ignored a
speed restriction on a sharp curve at the
tunnel leading to Boston’s Back Bay station.
The train left the rails and struck a commuter train.
Positive train control could have prevented both incidents, and Federal Railroad Administration concerns about increasing
speeds after the Back Bay accident prompted Amtrak’s Keith Holt and Larry Light to
develop Acses in 1992. They later contracted
with Alstom to complete and furnish the
system, which is different from the PTC systems freight railroads are developing.
The freight railroads’ PTC system requires constant communication with a backoffice server, while Amtrak’s system is less
dependent on radio communications. All of
the commuter railroads operating on the
Northeast Corridor have embraced Acses
because it is a proven system, and they all
have cab signals on their own railroads. Am-
NORTHEAST CORRIDOR PTC
Amtrak Engineer Pete Vilas runs an Acela
Express between Wilmington, Del., and
Baltimore. Al DiCenso
trak has a steering committee comprising
representatives of each commuter railroad
and Amtrak to ensure that all of the systems
will work together.
Amtrak’s system meets the requirements
of the 2008 PTC law, with features that
make the operation of high speed trains safe
and efficient. The equipment never removes
the control of the operation of the train
from the engineer, whose judgment exceeds
the capability of the system under normal
conditions. Instead, it gives visual and aural
cues that help the engineer handle the train
smoothly and efficiently. The signal system
that is conveniently and clearly displayed in
the cab gives a constant indication of the
correct speed for the area traveled, and advance warning of upcoming speed reductions. As the train approaches a speed restriction, information is shown on a display
screen, an alarm sounds, and required
speed and braking information are prominently shown on the instrument panel. The
engineer always knows whether he is within the safe limits established by the onboard computer.
In the event that the engineer becomes
distracted, the system provides audible and
visual warnings to grab his attention in
time to recover safe operation. If the engineer ignores these warnings, the system
takes over the operation of the train and
slows or stops it smoothly and safely as required by the signal conditions.
The braking profile provided by the onboard computer not only helps the engineer improve train handling, but working
with the cab signal system, it enables Amtrak to maximize track capacity by allowing fast trains to run closer together.
Washington D.C.
Perryville
PTC ON THE NORTHEAST CORRIDOR
Amtrak’s full-motion cab simulator at
the training center near Wilmington, Del.,
provides a deeper look into the Acses system. System General Road Foreman Don
Savidge and Operating Practices Senior
Analyst Jay Gilfillan set up a simulated
route for me to try out the system.
The simulator is a replica of an Acela’s
cab. Ahead of the windshield is a full-width
projection screen. With Savidge settled into
the engineer’s seat, Gilfillan starts the movielike scene of the right-of-way, complete with
lineside buildings, catenary supports, signals, and even bridges. We “move” as Savidge advances the power handle (Acelas
have no “throttle”), and the instruments
come to life. Our speed advances quickly to
that shown in the “signal speed” window of
the aspect display unit to Savidge’s right. The
speed allowed by the cab signal indication is
just above it, in this case green, or “clear
150”. Below that is the “track speed” window, which now indicates 135 for our location, but will change as we encounter curves,
bridges, and the like.
If Savidge does not make a control
movement for eight seconds or so, a beep
sounds, and the word ALERTER flashes on
his panel. He must then tap a small stalk at
his right to prevent another warning or the
system will begin braking. This assures the
system that the engineer has not become
disabled. A cab signal change will also set
the alerter off, and show the new signal indication as well as the required speed. At the
same time, a red border swings downward
around the speedometer dial to indicate the
new required speed. (Engineers call this the
“ring of fire.”) The engineer then has six seconds to begin braking to the required speed.
As long as he slows at the rate required by
the system’s braking profile computer, the
train is fully under his control. If, however,
he does not brake sufficiently to bring the
train down at the prescribed rate, the system
will add braking power to do so.
When a signal calls for a full stop, the
computer sets up the correct braking profile and continually monitors the train’s
speed and distance to the stopping point.
The train must be slowed at the prescribed
rate, and brought to a stop 500 feet before
the signal, where it cannot be moved again
until the on-board computer receives a
“stop release” command, either from a signal change that permits movement or by a
radio command from the dispatcher.
David James, one of the engineers responsible for the equipment that ties the
system together and makes it work, points
out a pair of yellow transponders located
between the rails near the control point
“Ragan,” just south of Wilmington. These
transponders communicate with the train
Wilmington
Trenton
New Brunswick
Transponder sets
Wayside signal
Cab signal
C (C150)
150 mph
125 mph
80 mph
30 mph
20 mph
C (C125)
Distant signal
CS (CS80) A (A30)
Cut section
(R-20)
Home signal
SS (SS 0)
tan = curve
from diagram
red = curve from data
0 mph
Onboard
display
Cab
signal
system
Civil speed
150
150
125
150
80
150
30
150
via an antenna mounted beneath the locomotive. The transponders’ primary function is to let the train’s on-board computer
know its exact location. On-board measuring equipment plots distance traveled, and
the transponders correct minor errors
caused by wheel diameter variation. The
transponders also feed the train information about distances to the next two transponder pairs, the next signal, or the next
interlocking.
A data radio link updates the train’s computer with real-time operating information
as it approaches each interlocking or junction. The transmitters for these radio links
are called base communication packages.
Placed along the railroad at strategic locations, they continually send information to
the on-board computers regarding temporary speed restrictions and route change details; they also enable dispatchers to keep
engineers informed as conditions change.
I also saw the system in action on the
Northeast Corridor during a cab ride on
Acela Express No. 2151 from Wilmington
to Baltimore. With engineer Pete Vilas at
the controls, we pass Ragan interlocking
just outside of Wilmington, and the Active
light on the train control system panel
blinks on. Vilas takes us up to the indicated signal and track speed of 135 mph.
Even at that speed, the cab is quiet enough
for normal conversation, and the ride is
smooth, thanks to the train’s tilt system.
Soon there’s a beep on the alerter, and the
track speed indicator flashes to 125, for a
curve ahead. This is the first of several
speed restrictions over the gently curving
line down Maryland’s Eastern Shore and
along Chesapeake Bay. Because no work
zones are active today, we won’t see a temporary speed restriction.
Vilas elects to adjust the train’s speed
New York
New Haven
20
150
Note: Transponder set at
distant signal locates stop
point prior to reaching
home signal. If home
signal is displaying stop
signal, stop and proceed,
or restricting, cab signal
will change to restricting
passing cut section which
will trigger the stop
command.
0
150
manually, using the power and brake handles. Acelas also have cruise control, and if
he wishes, Vilas can set the speedometer
“bug” at the desired speed and run “hands
off,” with the system controlling power and
dynamic braking, until the system calls for
a speed change. We reach Baltimore and
return to Wilmington aboard a Northeast
Regional train, which, even at a maximum
speed of 125 mph, seems sluggish compared to the Acela.
Transponders mounted between the rails
communicate train locations and speeds
between on-board computers and signals.
WHAT’S NEXT
On the Boston-New Haven segment,
Acelas operate at the maximum speeds permitted. AEM7 and HHP8 locomotives are
restricted to a 125-mph maximum. North of
New Haven, the route has stretches of 150mph running, with the balance mostly 135
mph. Between New York and Washington,
Acses is operational on two short stretches:
New Brunswick to Trenton, N.J., and Wilmington, Del., to Perryville, Md., each about
30 miles. These legs will be extended to the
entire Northeast Corridor, with completion
by the end of 2012. The New York-Washington segment will hold maximum speeds to
135 mph, partly because of curves and congested areas, but mainly owing to the age
and design of the catenary.
Under the positive train control mandate, Amtrak will extend the system by the
end of 2015 to include Metro-North between New Haven and New York; the Philadelphia-Harrisburg, Pa., “Keystone Corridor,” and the New Haven-Springfield,
Mass., line. The cost: about $100 million.
As the system covers these areas, commuter and freight railroads with trackage
rights over Amtrak must equip their locomotives with Acses technology. These operators include SEPTA, MARC, NJ Transit,
Metro-North, Norfolk Southern, and ConBoston
An antenna mounted under each Amtrak
unit picks up information from the
transponders. Two photos, Amtrak
necticut DOT. North of New Haven,
MBTA, Providence & Worcester, and CSX
in the Boston area are already equipped.
One additional change that will take
place as a result of the system’s implementation is to eliminate wayside signals except
at control points or interlockings. Instead,
the 10-aspect cab signal system will provide all necessary information between
control points to the engineer inside the
cab. This will eliminate the costs of keeping
the old-style signals in operation.
The next time you’re cruising along at
130 mph on the Acela Express, just remember, it’s thanks to the magic of a train control
system created nearly 20 years ago. 2
AL DiCENSO is semi-retired, living in Annapolis Md., and is vice president of the Railroaders Memorial Museum in Altoona, Pa.
PTC
Non-PTC
www.TrainsMag.com
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