In the large cities, it remains difficult and expensive to create more parking spaces for vehicles since they have almost reached their full occupancy. The lack of available parking places leads to the problem of traffic congestion and consequently to pollution, since drivers will spend a lot of time looking for a vacant parking place. Hence the need to establish a parking management system able to improve the exploitation of the existent parking places at a city level. This paper proposes a new multi agent system for parking vacancies detection based on vision techniques. We explore a network of interconnected video surveillance cameras and parking stations to provide an intelligent service to the drivers in order to facilitate their task and improve the exploitation of the parking resources. The proposed system introduces a new approach for parking spaces modeling and elaborates an adaptive approach for vacancies estimation in order to supply the driver with reliable information about the vacant parking spaces in the city according to the size of his vehicle.