1. A method comprising: calculating a first set of vehicle data for a first vehicle, wherein the first set of vehicle data describes future positions for the first vehicle on a first plurality of road segments; receiving a second set of vehicle data for a second vehicle, wherein the second set of vehicle data describes future positions for the second vehicle on a second plurality of road segments; identifying, using a processor, a common road segment included in the first plurality of road segments as the future positions for the first vehicle and included in the second plurality of road segments as the future positions for the second vehicle, wherein the first set of vehicle data includes a first probability that the first vehicle will travel on the common road segment and a second probability that the second vehicle will travel on the common road segment; and calculating a multi-vehicle probability, from multiplication of the first probability and second probability, that the first vehicle and the second vehicle both arrive at the common road segment.