The California Department of Transportation (Caltrans) District 9 has conducted an origin-destination study in the region roughly every 10 years since 1979. Each origin-destination study furthers Caltrans' understanding of how visitors use District 9’s highways. However, despite the studies' importance, the intercept surveys had been constrained by the previous data collection method. This method used a small data source paired with several assumptions and required intrusive traffic stops. This resulted in a labor-intensive survey process; it did not fully capture the breadth of information on travelers in the region.

In search of newer methods, Caltrans turned to RSG and our passive mobility data analytics services to produce a dataset that is comparable in utility to, but more cost-effective than, past survey methods. To ensure comparability with past surveys, we paired the big data we gathered with a small online survey. The big data and survey data were from the winter and summer months of 2019 and 2020. The survey delivered additional information from respondents and provided greater confidence in the validity of the big data results. Our findings are assisting Caltrans District 9 planning staff with predicting traffic and economic changes in the region. District 9 and local agencies will also use the results from our work to develop strategies and recommendations.