1. ARRC Collision Avoidance System
2005 ASME/IEEE Joint Rail Conference
March 16-18, 2005
Presented by
Chinnarao Mokkapati
Robert D. Pascoe
Union Switch & Signal Inc.

3. Alaska Rail Road Facts (2003 Data)
Employees
722 Year-round
10.8 average years of service
43.2 average age
Operating Statistics
446,162 Passenger ridership
8,324,395 Freight tonnage
102,292 Revenue car loads
Trains per day
33 Freights
14 Passenger - Summer
1 Passenger - Winter
Operating Data
Miles of track
466 main line
59 branch line
86 yards/sidings
611 Total
Rolling Stock
1,625 Freight cars
42 Passenger cars
60 Locomotives
Train Control
~500 miles of DTC
~30 miles of CTC

4. ARRC CAS Objectives
PREVENT TRAIN TO TRAIN COLLISIONS BY ENFORCEMENT OF AUTHORITY LIMITS
ENFORCE SPEED RESTRICTIONS
PROVIDE PROTECTION FOR ROADWAY WORKERS AND EQUIPMENT
IMPROVE EFFICIENCY OF OPERATIONS
INCREASE CAPACITY

5. FRA Requirements Generation of safe mandatory directives
Enforcement of authority limits
Enforcement of speed restrictions
Protection of Maintenance-of-Way workers and equipment
Rule 236 Subpart H compliance required
Performance Std: New system must be as safe or safer than the system being replaced
Operating conditions, parameters, constraints must be defined
Structured qualitative and quantitative assessment of safety (Base Case and New Case) required
Product Safety Plan or Safety Case

6. Some Definitions
CTC and DTC Operation

7. Some Definitions
Track Bulletins Used in System

8. Collision Avoidance System

13. General Philosophy of CAD and OSS Subsystems
Block 3
Block 6
Block 5
Block 7
Block 11
Block 9
Track
Servers
Existing
Comms
(( ))
Dispatcher
Work
Stations
Vital
Independent
Check of
LOA, Bulletins
CAD
OSS

14. Vital Checks Done by OSS
Via the OBC, the position of all trains are known to the OSS
‘Occupies’ Virtual blocks
‘un-occupies’ Virtual blocks
Checks Bulletins associated with Blocks & LOA

15. OSS Hub Physical Architecture
Microlok II
RS423
Network
Interface
Adapter
Ethernet
CAD Subsystem
Ethernet Switch
OSS Hub Physical Architecture

16. Software in MicroLok II Units
Block 1
Block 3
Block 6
Block 5
Block 7
Block 11
Block 13
Block 9
S#5
S#7
North
Executive Software
Operating System
Application Processing
Serial Communications Control
Safety Diagnostics
User Interfaces
Event Logging
Application Data Tables
Track Sections defined as Virtual Blocks
Switch locations
Other identifiable points

17. OBC Requirements: Profile Generation
Train Location and Speed Determination
Digital Track Data Map
Communication via Digital Radio

18. LOCATION AND SPEED DETERMINATION
DGPS
Accelerometers
Tachometers
Digital Map
The result is that the OBC vitally
determines its location on the rails
and transmits its location to Central

19. New On Board Computer (OBC) - ATP

20. Existing Network Communication System

23. Communication Backbone

24. MONITORING DEVICES
Rail Integrity
Switch Position
Signal Aspect in CTC

25. The Locomotive’s ATP Interrogates Three Wayside Devices
using a short range data radio:
A Rail Integrity Device
Broken Rail Detection
MicroTrax
A Switch Position Device
Normal or Reverse
A Wayside Signal Device
Aspect
Locomotive
Device
Broken rail
Short Range
Data Radio
Device N R
Locomotive
Short Range
Data Radio
Device
Aspect
Locomotive
Short Range
Data Radio

26. CAS Safety Assurance
Safety resides in OSS and OBC, though CAD performs some safety-related functions
OSS is implemented on US&S MICROLOK II Platform
OBC implemented on US&S MICROCAB Platform
These platforms use a combination of Inherent Fail-Safety and Diversity & Self-Checking safety architectures
Certified by independent safety assessors
Extensive service history

27. CAS Safety Assurance Compliance with FRA Rule 236 Subpart H
Risk analysis of CAD-only DTC/CTC Operation (Base Case)
Derive safety requirements for CAS
V&V of CAS design and operation
Risk analysis of CAS (CAS Case)
Risk assessment
Show CAS provides higher safety than CAD-only DTC/CTC operation

28. Risk Analysis Conduct Hazard Analyses Determine MTTHE using FFTA PHA
O&SHA SSHA
Determine MTTHE using FFTA

29. Derive safety requirements for CAS
Potential hazards in Base Case
FFTA of CAS elements
CAS subsystem safety requirements

30. V&V of CAS design and operation
Normal operation
Systematic faults
Random hardware faults
Common Mode faults
External influences

31. Risk analysis of CAS (CAS Case)
Conduct Hazard Analyses
PHA
O&SHA SSHA
Determine MTTHE using FFTA

32. Risk Assessment
Show CAS provides higher safety than CAD-only DTC/CTC operation
Submit PSP
20 elements required per FRA Rule

33. Project Timeline 11 / 2005 CAD SAT 06 / 2006 Office Safety and OBC FAT
2007
4/16/2005 -
10/16/2005
2005 Peak Season
4/15/2006
10/15/2006
2006 Peak Season
11 / 2005
CAD SAT
Complete
2 / 2007
Revenue Service
10 / 2006
Office Safety and OBC
SAT
06 / 2006
Office Safety and OBC FAT
1 / 2006
CAD Cutover
complete
4Q 2004
System
Definition

34. Conclusions CAS is a practical, relatively inexpensive PTC System
Scalable for larger systems
Uses proven safety architectures
Credible, straight-forward safety proof