A system is described that infers that a user will need to complete a trip and selects a transportation service that the user can use to complete the trip. The system, predicts a time to request a vehicle associated with the transportation service for completing the trip such that the request has sufficiently high degree of likelihood, of causing the vehicle to arrive at a future location by a final departure time: the final departure time being a latest time at which the user is predicted to need to begin traveling. Responsive to determining that a current time is within a threshold amount of time of the predicted time, the system sends, to a reservation system associated with the transportation service, a reservation request for the vehicle associated with the transportation service for completing the trip.