THE JANUARY 17, 1994 NORTHRIDGE EARTHQUAKE IMPACTS ON THE INTERSTATE-5 AND THE STATE ROUTE-14 COMMUTE BEHAVIOR IN LOS ANGELES COUNTY

Southern California was struck by a 6.8 magnitude earthquake (measured on the Richter scale) on January 17, 1994 (Northridge Earthquake) which caused extensive damage to some of the region's freeway system. The Golden State Freeway (Interstate 5), the Antelope Valley Freeway (State Route 14), and their Interchange in and around the city of Santa Clarita were significantly damaged. Detours were quickly established and work on the damaged (or destroyed) freeway segments was initiated within a few days. Traffic volumes, occupancy counts, and travel time runs were frequently conducted to capture the changes to pre-quake conditions as repair work progressed. Various surveys were also taken to ascertain commute behavioral changes. The results indicated that the majority of people were satisfied with the available detour routes. Those who utilized the established temporary High Occupancy Vehicle (HOV) lane on SR-14 (one lane each direction) saved as much as 9 minutes compared to those on the mixed flow lanes during the morning peak period (southbound) commute. About 7% of the I-5 pre-quake trips were discontinued through the two corridors after the quake because of increased traffic congestion, inconvenience, telecommuting, and change in work location. Approximately 9% of the SR-14 pre-quake trips were also discontinued through the damaged sections due to the same reasons. Metrolink ridership on the Santa Clarita line increased significantly (from 1,000 boardings per weekday pre-earthquake to 22,000 per weekday in late January, 1994). This, however, decreased to about 4,000 boardings per day in July.