From the study
The data — which come from safe-driving apps that drivers voluntarily enroll in — show that cellphone use prior to crashes is undercounted in police reports by a factor of at least 7.
Since police reports do not always record crash times and locations with perfect precision, crashes that occurred within the same 15-minute window and within the same one-mile radius were determined to be a match.
This whole study is worthless. There’s also a whole ton of assertions with zero source.