Fiber-optic DAS sensing of transportation patterns during the COVID-19 pandemic in Palo Alto, CA

Abstract:

Throughout the recent COVID-19 pandemic, real-time measurements about the shifting use of roads, hospitals, grocery stores, and other public infrastructure became vital for government decision-makers. Mobile phone locations are increasingly assimilated for this purpose, but an alternative, natively anonymous, absolute method would be to use geophysical sensing to directly measure public infrastructure use. Here we demonstrate how fiber-optic Distributed Acoustic Sensing (DAS) connected to a telecommunication cable beneath Palo Alto, CA successfully monitored traffic during the unprecedented disruption in transportation activity, including major reductions associated with COVID-19 response. Continuous DAS recordings of individual vehicles were analyzed using an automatic template-matching detection algorithm based on roadbed strain. In one commuter sector, we found a 50% decrease in vehicles immediately following the order, but near Stanford Hospital the traffic persisted. The DAS measurements correlate with mobile phone locations, suggesting geophysics would complement future digital city sensing systems. Because DAS is a broadband technology, we also investigate the contribution of vehicles to the seismic background of this urban area.