Creating resilient emergency plans by incorporating travel time reliability into the evacuation process

Transport networks are one of the lifeline systems that serve the community by providing essential mobility for personal travel and goods movement, as well as for access by emergency services. The performance of transport networks is threatened by the increased frequency and severity of floods, cyclones and bush fires as an effect of climate change, and therefore we need to adapt our networks and service provision to cope with new climate regimes and human settlement patterns. Given a definition of travel time reliability which assesses the probability of finishing a trip before a specified time (travel time threshold), we propose a travel time reliability metric for emergency and evacuation plans which considers demand and capacity uncertainties as well as other behaviour related factors that are of concern in evacuation planning. This metric measure the additional travel time during the evacuation process based on one specific distribution, the Burr distribution that has been found to represent the distribution of variations in journey travel times. The three parameter version of the Burr distribution is a continuous distribution with two shape parameters and one scale parameter. It can be used to generate refined travel time reliability metrics that reflect the observed characteristics of positive skew and long upper tails in travel time variability. The new travel time metric can be used as a performance measure in emergency service and evacuation planning plans. We conclude that this metric can play a vital role as a decision support tool for more robust and reliable evacuation plan in order to plan and provide more resilient transport systems.