Maintenance trains travel in convoy. In Australia, only the first train of the convoy pays attention to the track signalization (the other convoy vehicles simply follow the preceding vehicle). Because of human errors, collisions can happen between the maintenance vehicles. Although an anticollision system based on a laser distance meter is already in operation, the existing system has a limited range due to the curvature of the tracks. In this paper, we introduce an anti-collision system based on vision. The proposed system induces a 3D model of the track as a piecewise quadratic function (with continuity constraints on the function and its derivative). The geometric constraints of the rail tracks allow the creation of a completely self-calibrating system. Although road lane marking detection algorithms perform well most of the time for rail detection, the metallic surface of a rail does not always behave like a road lane marking. Therefore we had to develop new techniques to address the specific problems of the reflectance of rails.
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