Vehicle information processing apparatus and vehicle information processing program

A vehicle information processing apparatus detects the relative positions multiple vehicles that travel on a road having multiple lanes in the same direction. The apparatus includes a vehicle travel information acquisition unit configured to acquire at least one of position information and speed information measured for a first vehicle, and at least one of position information and speed information measured for a second vehicle included in the multiple vehicles, and a vehicle travel information processing unit configured to successively compare acquire first vehicle travel information with second vehicle travel information acquired, and determine that reciprocity which is attribute information indicating a state in which the first vehicle and the second vehicle travel in different lanes is established between the first vehicle and the second vehicle if it is determined that an event that cannot occur when the first vehicle and the second vehicle travel in the same lane occurs.