University of California Institute of Transportation Studies

In 2017, California passed Senate Bill 1 (SB1) to bolster transportation infrastructure funding. Using data primarily from the California Department of Transportation (Caltrans)’s official SB1 progress reports, we analyze the severity of cost overruns, delays, and cancellations across SB1 Transportation Projects. Although events such as the COVID-19 pandemic likely caused some of these negative outcomes, our statistical models show consistent patterns of overruns associated with fiscal periods, programs, and geographic locations. Our results indicate that the common 20% contingency is generally insufficient, indicating the need for better risk estimation in project planning. We also suggest amplifying data transparency on project performance and re-evaluating project selection criteria to avoid rewarding underestimation of project costs and duration and penalizing accurate estimation.