A maximum-flow approach to dynamic handling of multiple incidents in traffic evacuation management

Contemporary terrorists have made public transportation a new theater of operations. Specifically, attacks on the urban transportation system can cause great disruption and alarm, which are the traditional goals of terrorism. The unexpected and stochastic character of terrorist attacks poses unique challenges to those responsible for security. Since the threat of terrorism is obscure and security measures are costly, it is hard to justify the expenditures before an attack. Security against terrorism therefore tends to be reactive. In this paper we propose new ITS technologies to enhance the surface transportation aspects of homeland security, by providing more efficient and safer evacuation for general public in case of terrorist attacks or other human caused disasters. In particular, we extend our existing work on developing a smart traffic evacuation management system (STEMS), by enhancing it with capabilities to adapt to the dynamics of the traffic environment, by leveraging real-time information obtained from sensors or other surveillance technologies. STEMS handles the unexpected aspect of terrorist attacks or other unpredictable disasters, by generating evacuation plans dynamically, when given an incident location and scope. To handle traffic dynamics, STEMS will continue to revise the initially generated plan, during the evacuation operation, to keep it consistent with the continuously changing traffic conditions. The advantages of this revision process are two-fold: first, it ensures that traffic will not be directed towards congested areas; and secondly, it decreases congestion by spreading the traffic from currently congested segments to alternative routes. Our simulation studies show that employing real-time information greatly improves STEMS performance and therefore, evacuation efficiency.