This article presents a new approach to adhesion control for railroad traction. Based on a combined torque and speed observation the controller detects the actual adhesion utilization at the wheel and applies an adequate torque limitation. Hence the traction unit optimally takes use of the available adhesion. No measurement of the absolute train velocity is needed. The effectiveness of the proposed method has been investigated by railroad tests with a subway electric traction unit. The results and their good conformity with computer simulation are presented in detail.