Abstract: In a method for determining accuracy of arrival time information, one or more ETAs are received from a transit service provider. Each ETA indicates a time at which the transit service provider purports to be able to provide a transit service at a respective location. An ETA corresponding to a target location of a mobile communications device is determined and sent to the mobile communications device for display to a user. User activity data indicative of locations of the mobile communications device over time is logged, and processed to determine both (i) that the user did use the transit service provider and (ii) the time at which the transit service was actually provided at the target location. A time difference between the ETA and the actual arrival time is then calculated.