Maintenance trains travel in convoy. In Australia, only theudfirst train of the convoy pays attention to the track signalizationud(the other convoy vehicles simply follow the precedingudvehicle). Because of human errors, collisions can happenudbetween the maintenance vehicles. Although an anticollisionudsystem based on a laser distance meter is alreadyudin operation, the existing system has a limited range due toudthe curvature of the tracks. In this paper, we introduce anudanti-collision system based on vision. The proposed systemudinduces a 3D model of the track as a piecewise quadraticudfunction (with continuity constraints on the function andudits derivative). The geometric constraints of the rail tracksudallow the creation of a completely self-calibrating system.udAlthough road lane marking detection algorithms performudwell most of the time for rail detection, the metallic surfaceudof a rail does not always behave like a road lane marking.udTherefore we had to develop new techniques to address theudspecific problems of the reflectance of rails.
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