Statement of purpose Rideshare companies such as Uber and Lyft have facilitated over 20 billion trips worldwide since the technology launched in 2010. Ridesharing could theoretically reduce alcohol-involved motor vehicle crashes by replacing drunk driver trips.

Methods/Approach This case control study used highly spatially and temporally resolved trip-level rideshare data and motor vehicle crash data for Chicago from November 2018 to December 2019. The units of analysis were motor vehicle crashes in the city of Chicago. Cases were crashes that police indicated were alcohol-involved. Controls were crashes in the same census tract, matched 1:1. The exposure of interest was the density per square mile of rideshare trips that were in progress at the time of the crash, calculated using a kernel density function around active trip route lines. Control variables were taxi trip density, time of day, day of week, public holiday, temperature, precipitation, and month. A conditional logistic regression compared alcohol-involvement to rideshare trip density.

Results There were 962 alcohol-involved motor vehicle crashes and 118,913,157 rideshare trips during the fourteen-month study period. Rideshare trip density was 69.0 per square mile at the location of case crashes and 105.7 per square mile at the location of control crashes. After controlling for covariates, the conditional logistic regression model identified that an increase of 1 rideshare trip per square mile at the crash site was associated with 0.2% decreased odds that the crash was alcohol involved (OR = 0.998; 95%CI: 0.996, 0.999). There was no association for taxi trips.

Conclusions Increased ridesharing activity was associated with decreased risks that motor vehicle crashes were alcohol involved.

Significance Over 10,000 people die in alcohol involved motor-vehicle crashes annually. Rideshare trips may replace drunk driver trips, thereby reducing the considerable injury burden due to alcohol-involved crashes.