1. Karl W. Berger, P.E.
DCM, Inc.
Centreville, VA
IEEE/ASME National Capital Land Transportation Committee
December 8, 2009

2. Long term inadequate inspection allowed
fleet-wide wheel defects.
Investigation revealed underlying problem
caused by poor integration of car braking
systems with Automatic Train Protection
(ATP).
A temporary fix completely eliminated
wheel damage.
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3. Opened in 1992 as a single-track line.
Central Line + 2 branches = 30 miles.
Serves 33,600 passengers per day.
53 large LRVs by ABB (Bombardier).
Originally equipped with Automatic Block
Signals (ABS) and magnetic Trip Stops.
Several collisions revealed deficiencies
with Trip Stops.
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4. Progressively upgraded Central Line
between 2004 and 2006.
Replaced ABS with Cab Signaling with
Automatic Train Protection.
Removed wayside signals and trip stops.
Reduced headways from 17 minutes to 8
minutes.
Improved service reliability.
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5.  Wayside signal system impresses each
track block with a speed codes.
 Speed code inductively coupled to lead
vehicle in train.
 Operator normally controls train below
received speed code.
 Audible alert if operator exceeds speed.
 Automatic Train Protection applies brakes
if operator or vehicle fails to respond.
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6. Guaranteed Emergency Brake Rate
(GEBR) of 1.5mphps (0.67 m/s2)
implemented with vital systems.
GEBR achieved with single-point failures
in braking systems.
Signal block lengths designed to include
adjustment for grade and curvature.
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7. Condition Cab Signal Command LRV Response
Speed <
Speed Code – 1.5 mph
Normal Operate Normally
Speed =
Speed Code – 1.5 mph
Propulsion Disable Inhibit Propulsion
Speed >
Speed Code + 0.5 mph
Penalty 1 (Overspeed) Apply Full Service
Braking
Penalty 1 Active
AND
Decel < 1.5 mphps
for > 3 seconds
Penalty 2
(Brake Assurance)
Apply Emergency
Brakes (vital)
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8. APPROACH8 – Used at interlockings.
Immediate Penalty 2 Emergency Brake on
Loss of Speed Code or Overspeed.
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9. Constraints due to nearly obsolete car
control computer.
Added redundancy to remove single-point
failures in friction and track brake systems.
Added two emergency magnet valves for
ATP Emergency Brake applications.
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10. April 2008 – broken wheel found on LRV
prior to entering service.
Fleet inspection found many wheels with
excessive damage and flats.
Investigation started.
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11. The fall leaf season intensified the
problem.
Northern half of system shut down in early
November 2008.
Only 7 cars operational by mid-November.
Intensified research into problem and
solutions.
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13. Causes:
• Inadequate slide control in service braking
• No slide control in Emergency Braking
• Problems induced by other defects.
Distribution:
• Brake Assurance – General 36%
• Brake Assurance – Greasy Rail 22%
• APPROACH8 anomaly 21%
• Unknown/Unaccounted 14%
• Operator commanded 7%
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14. Component failures in signal cabins
caused momentary loss of speed code at
interlockings. (APPROCH8 Anomaly)
Excessive grease on curves reduced
adhesions.
Accounted for 43% of Emergency Brake
flats.
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15. Inadequate slide control in service braking
– typically 0.8 to 1.2 mphps during slide.
No slide control in Emergency Braking.
Higher adhesion demand on unpowered
center trucks.
Maintenance was not refilling sand boxes.
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17. LRVs equipped with six electromagnetic
track brakes (one pair per truck) .
Each pair provides ≈ 0.8 mphps.
Sliding wheels + Track Brakes > 1.5mphps
Not fail safe – power required for
actuation.
Cannot be used to meet GEBR.
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19. Energize one pair of track brakes on ATP
overspeed (Penalty 1).
Track brakes add ≈0.8 mphps to full
service brakes. GEBR satisfied with sliding
wheels.
Vitality provided by existing Emergency
Brake response.
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20. Added two diodes and an On/Off switch.
Effectiveness verified by test.
Vitality of ATP confirmed by Failure Mode
Effects and Criticality Analysis.
Entire fleet retrofitted and tested in one
week.
Full service over entire system restored by
the end of November 2008.
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22. Wheel flatting eliminated.
Center Truck track brakes shoe life
reduced to 3 months.
ATP software modification added
discrimination and restored acceptable
shoe life.
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23. Improve dynamic brake slide control.
Improve friction brake slide control.
Replace car control computer.
Improve ATP integration.
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