Measuring of railway structure clearances is a very practical issue, and the operation itself is performed all over the world using various measuring systems. The measurement is aimed chiefly at determining the limits of space that no structure (e.g. a building) located close to the railway track may cross. The paper demonstrates flaws and advantages of particular systems and provides a technological summary of measuring equipment utilized in them. In those systems the measurement of structures is referred to the global system of coordinates, and later, following the detection of rail heads, a transformation to the rail axis arrangement takes place. The preliminary analysis leads to a conclusion that the accuracy of rail clearance measurement is higher in the case of specialized systems as compared to universal ones. On the basis of experience drawn from literature and earlier tests, a decision has been made to proceed with the construction of a rail clearance measurement system in Poland, at the University of Science and Technology in Cracow. This paper presents a research on the prototype of the rail clearance measurement system constructed at the University. The heart of the system involves laser scanners installed on a flatcar and digital cameras. The base of the system includes scanners, which capture data in a continuous way, and photogrammetric cameras, which yield digital images. The cloud of points obtained from a laser scanning is colorized, which causes that such information can replace a classical texture model.