Vehicle velocity and tire-road friction conditions are crucial variables to determine the vehicle behaviour in all maneuvers; therefore, all active control systems must either be robust with respect to them, or adapt their parameters to their current value if they can we propose to employ be either measured or estimated. A direct measurement of the vehicle velocity in slipping conditions is in general complex and impractical, and the same holds true for tire-road friction conditions. In this paper, sliding mode observers are proposed to estimate vehicle acceleration, which can be used both as in input for existing algorithms for vehicle velocity estimation and for estimating the current road conditions. Experimental results support the validity of the proposed approach.