MDS gives cities access to historic and real-time rider location data.  Transportation officials claim the data is anonymous, but researchers have found that it’s relatively easy to figure out who a person is based on where they’ve been.

According to Paul Ohm, a Georgetown University law professor and privacy expert, describing location data as anonymous is “a completely false claim” that has been debunked in multiple studies. Ohm says, “Really precise, longitudinal geolocation information is absolutely impossible to anonymize.”

With very little analysis, location data can reveal a rider’s home, work, travel, and identity. MDS compounds the risk because it shares trip start and stop locations with cities immediately, allowing those with access to the data to intercept or surveil individuals.

For vulnerable communities, like survivors of abuse and hate-motivated crimes, the risks from exposing their location are high. Riders could also face a surveillance dragnet as cities share MDS data with law enforcement. And who can say what activities or relationships any given individual might want to keep private from friends, employers, competitors, or the government?