Tyre/road-friction determines which driving manoeuvres are physically possible and is therefore of utmost importance for vehicle safety. At the Department of Automotive Engineering (fzd, Head: Prof. Dr.-Ing. B. Breuer) of Darmstadt University (THD) research on the on-board measurement of tyre/road friction was started 1988 and has since then been funded by Deutsche Forschungs-Gemeinschaft (DFG) and within the European research-project PROMETHEUS. Methods and instruments described in this paper represent its present state. Two different methods of friction detection are proposed: one computes a μ-slip-curve from contactless measurements of the road surface, the other derives friction from signals gained inside the tyre. Beside several influences on the friction level, which are measured in their entirety on real roads under natural conditions, some effects of local tyre behaviour are discussed.