A traffic monitoring system comprises at least one sensor station (2) and an interferometric interrogation system (9); wherein the at least one sensor station (2) comprises at least one optical fiber sensor (5) deployed in a highway (1); and wherein the interferometric interrogation system (9) is adapted to respond to an optical phase shift produced in the at least one optical fiber sensor (5) due to a force applied by a vehicle passing the at least one sensor station (2).