Abstract: A driving system allows an invalid chair having a seating structure, wheels on both sides of the seating structure and at least one front stabilizing wheel, to pass obstacles. The driving system has arms secured to both sides of the seating structure and on which shafts of the wheels are arranged slidingly within two extreme positions. Cranks are on both sides of the seating structure and rotary cross engagement members are at the rear and on both sides of the seating structure and have arms which are terminated with adhesive end pieces. Each crank is connected to a respective rotary cross engagement member through a geared transmission for transmission of rotary movement of the crank to the rotary cross engagement member, and the geared transmission is provided with a flap for preventing reverse rotating of the crank.