Need for Bridge Monitoring Systems to Counter Railroad Bridge Service Interruptions

This paper describes an effort to understand the types of railway bridge irregularities that cause service interruptions and to use this information to evaluate the need to develop bridge monitoring systems. Existing monitoring systems and other mitigation techniques were also considered. The study described in this paper considered the frequency and severity of such service interruptions and estimated that the annual risk exposure from bridge irregularities cost tens of millions of dollars; the estimate did not include the cost of consequent train delays. The analysis showed that the largest contributors to irregularities were scour and other bridge hydraulic issues. The next most frequent causes were strikes from marine traffic and strikes from highway traffic. Other large contributors were damage by derailed trains, fire, failed structural members, and movable bridge irregularities. The number of train delays from structural failures was minimal, primarily because of effective inspection and maintenance procedures implemented by North American railroads. A risk control matrix was developed to match potential irregularities with existing control measures and to identify those areas in which additional controls might be warranted. Results suggested that track displacement detectors, tilt monitors, and midspan displacement monitors should undergo additional investigation. Bridge inspection is an effective way to avert many potential losses and presents an opportunity for railway workers to detect defects as well. Workers trained to recognize bridge-related irregularities may be a cost-effective way to reduce losses from bridge service interruptions.