than 24 or 48 h, as in the case of a hurricane evacuation). When the time to evacuate is considerably less, people may need to be evacuated directly from their current locations. The timing and magnitude of certain types of disasters may require faster reactions. People may receive short notice about the emergency and their need to evacuate, providing little or no time to return home before evacuating. In addition, for some disasters, the spatial extent of the evacuated area may change over time. This problem may be exacerbated by congestion around the evacuated area. For example, to manage traffic flows effectively in the event of a short-notice disaster such as a wildfire or flash flood, it may be useful to know which areas must be evacuated first and the likely impact on roadway congestion throughout the region.Several studies have been conducted on estimating demand characteristics for an evacuation, particularly focusing on the factors of trip generation, trip distribution, and trip timing. Some research has focused on estimating a trip generation model, such as the logistic model and the neural network model, using hurricane survey data (1-5). These models estimate a probability of leaving an area as a function of time as the disaster progresses. Other models estimate evacuation demand using socioeconomic data (6, 7). Similar to these last two studies, the present study considers the case without existing evacuation survey data for estimating a model of trip generation; existing trip generation data from existing urban planning models are used; such is the common situation faced by most regional transportation and emergency management agencies. In addition, models used for trip distribution for evacuation include the gravity model, the intervening opportunity model, and the multinomial logit model. Finally, a type of logistic model has been used for vehicle loading, describing the time of departure (6-8).Methods of estimating demand for a short-notice evacuation have not been discussed at length in the existing literature. In this paper, an estimation process is proposed for a short-notice evacuation. The method uses "on-hand" data typically generated through existing travel demand models at many metropolitan planning organizations. In this context, the proposed trip generation and distribution models are developed using existing trip matrices based on existing, calibrated travel demand models. It generally assumes that no separate set of behavioral data is available for estimating evacuation demand. Trip matrices are suggested for use as the basis for generating trip distribution; this trip distribution approach was inspired by Southworth (7). Additionally, a time-dependent evacuee departure model is proposed that considers a multiple-zone evacuation strategy related to that of Tweedie et al. (8).
Approach to Modeling Demand and Supply for a Short-Notice EvacuationHyunsoo Noh, Yi-Chang Chiu, Hong Zheng, Mark Hickman, and Pitu Mirchandani 91 As part of disaster mitigation and evacuation planning, planners ...
