Toll collection system, position measurement method, and program

A toll collection system (1) carries out toll collection communication with an on-board device (A1), among on-board devices (A1) mounted in vehicles (A) traveling in a lane, that is present within a defined communication region that is defined for the lane. The toll collection system (1) is provided with: a vehicle detector that detects the entrance of a vehicle (A) into the lane; a model determination unit (37) that determines the model of the vehicle (A) in a step occurring before the vehicle (A) is detected by the vehicle detector; and a position measurement unit (31) that, on the basis of a position measurement signal (D4) obtained by receiving, via a predetermined position measurement antenna (22A), a radio wave transmitted by the on-board device (A1) after being detected by the vehicle detector, measures the position of the on-board device (A1) that transmitted the radio wave. The position measurement unit (31) measures the position of the on-board device (A1) on the basis of the arrival angle of the radio wave measured using the position measurement signal (D4), and the installation height of the on-board device (A1) estimated from the determination of the model of the vehicle (A).