Highway System Performance Measures and Economic Impact

As demonstrated in recent disasters such as the 1994 Northridge and 1995 Hyogoken-Nanbu (Kobe) earthquakes, urban areas can suffer potentially large economic losses when highway transportation systems are damaged in seismic events. This paper addresses the development of performance measures for highway systems that are suitable for estimating the economic impact of earthquake damage. Economic impact is here defined as the loss of economic production or output levels (e.g., gross regional product) in the area affected by the disaster which may be caused either directly or indirectly by highway service disruption. It does not refer to the cost to repair physical damage. In this paper, summary measures of system performance are proposed and evaluated using data from Northridge and Kobe. Particular attention is paid to the improvement in system performance as damaged portions of the network are restored in the weeks and months following the earthquake. Using actual traffic volumes as an indicator of economic activity in the restoration period, an explanatory model is developed for the Kobe case using multiple regression analysis. Highway system performance is found to be the most important factor influencing traffic recovery, but its influence varies with the phase of restoration. A framework is then proposed by which this model can be used to estimate the reduction in economic losses associated with alternative repair strategies and pre-earthquake mitigation measures. Proc. of the 7th U.S.-Japan Workshop on Earthquake Disaster Prevention for Lifeline Systems, Seattle, Washington, USA, Nov. 4-7, 1997.