PURPOSE: To check occurrence of slippage and smoothly as well as promptly restore slippage should it occur.

CONSTITUTION: Regarding a self-running vehicle slippage preventive measure preventing slippage of a self-running vehicle by detecting acceleration α of a driving wheel as well as a wheel slippage index Vd relating to the vehicle speed and regulation engine fuel injection quantity using such slippage index Vd and the acceleration α, (1) when Vd≥VS or Vd>VS, the fuel injection quantity is reduced by a specific quantity 'q'. Thereafter, (2) when α≥α+ (or α>α+), the fuel injection quantity is reduced by the specific quantity 'q', and (3) when α+>α>α- (α+≥α>α-, or α+>α≥α- or α+≥α≥α-), the present fuel injection quantity is maintained. (4) When α≤α- (or α<α-), the fuel injection quantity is increased by the specific quantity 'q' and successively performed per specific time Ts conforming to the cases of above (2), (3), (4) taking placed, making it a condition that until the slippage index Vd reashes below the specific value VS (Vd<VS).