Give an analysis or just an explication for the systeme ,how much sensors we need on the double  railway , remembring that not all trains run at full speed which is 120km/h, and not all trains will be 750 meters long. 

Aim: Design of an automated unmanned railway level crossing Context: On a double railway line, it is necessary to automate a level crossing to make crossing the line safer for vehicles and avoid the need to have someone constantly present to close and open the barriers. Some data: Maximum length of a train set: 750 metres; Maximum speed of circulation: 120 km.h*; Minimum time between closure of the barriers and passing of a train: 60 seconds; Running direction: trainsets can run in any direction on any of the railway tracks. Work to do: Design a system based on wheel detectors and a controller capable of fully automating the level crossing. The project should contain the location of the required wheel detectors and their distance from the level crossing and the algorithm to run on the controller, which should read the information coming from the wheel detectors and act on the closing/opening of the barriers and approaching train signal lights. The algorithm can be presented as a flowchart, a state machine, or using pseudocode and must be detailed enough to understand how it works in all possible situations.