Chapter Four – Serviceability Methods

This chapter provides a comprehensive review of the definition, development, and application of a number of approaches to vulnerability analysis, with a focus on the serviceability of a transportation network and the transport consequences of network failure and degradation under different conditions, including traffic congestion and incidents, severe weather, and natural disasters. The methods cover a range of different intensities and extensions of disruptive incidents, from link-specific incidents and incident durations of a few hours, to area-wide disruptions and consequences lasting for days or weeks. Most of these methods require consideration of adverse changes in travel costs, notably as increases in travel times and delays as a consequence of network failure, blockages, or service disruption. The performance indices and metrics invoked in these methods often bear directly on the performance measures commonly employed by transportation system planners and managers, and relate directly to system performance and diagnostics for improved performance.