Abstract
This study evaluates the traffic crash trends on the two interstate highways in California “SR-99” and “I-80”, located in Caltrans District 3. This investigation shines a light on what happened a year before, during, and after the implementation of state of emergency and lockdown orders. The data were collected from Performance Measurement System (PeMS) for the period 2019 through 2021 and the crash frequencies were analyzed. The result shows an overall reduction of traffic crashes on Highway “I-80” during the Covid-19 lockdown compared to 2019 and 2021. On highway “SR-99”, there was a reduction of traffic crashes compared to 2019 and 2021; however, there was a 0.1% increase on the proportion of crash severity injury category on highway “SR-99” and “I-80” compared to 2019. The most important factors that affected road traffic collisions are decreased vehicle-miles traveled with reduced congestion and increased speeding. The increase in the proportion of severe injury crashes observed aim the outbreak of Covid-19 pandemic attributed to the increase in traffic speeds in the selected highways that were analyzed. Study findings can inform transportation agencies on how and where to allocate the resources to help upgrade safety due to unexpected changes in mobility trends like those caused by Coronavirus.