I. INTRODUCTION
EXPERTS estimate that the railway industry will receive
US$300 billion worth of global investment for development,
upgrading, and expansion over the five years from
2009 [43]. Ollier [98] noted that effective management of rail
infrastructure will be vital to this development, upgrading, and
expansion, particularly if coupled with a move to intelligent
infrastructure [39]. A key part of the management will be condition
monitoring. Condition monitoring detects and identifies
deterioration in structures and infrastructure before the deterioration
causes a failure or prevents rail operations. In simple condition
monitoring, sensors monitor the condition of a structure
or machinery. If the sensor readings reach a predetermined limit
or fault condition, then an alarm is activated. However, this sim-