This paper derives properties of various estimators of length intensity of stationary random fibre processes in Rd. The projections of the process onto R1 and intersections with a system of parallel (d - 1)-dimensional hyperplanes are studied. The estimation variances are expressed by means of pair correlation functions of appropriate random measures. The results are formulated for the anisotropic models in arbitrary dimension. Explicit formulas are obtained for the anistropic Boolean segment process.