the requested vehicle speed or the target vehicle speed vd of the vehicle 1 can be determined by referring to the expected value this means that the requested vehicle speed or the target vehicle speed vd of the vehicle 1 can be corrected at every control cycle therefore in the illustrated embodiment even if the distance from the point p 1 a where the control is started to the descending slope starting point p 2 a is long the fuel injection amount is adjusted by correcting the requested vehicle speed or the target vehicle speed vd at every control cycle and thus an error between the vehicle speed va at the descending slope starting point p 2 a and the target vehicle speed vt when entering a descending slope can be made small by reducing an error between the vehicle speed va and the target vehicle speed vt when entering a descending slope in the illustrated embodiment as a numerical value of the distance l from the point p 1 a where the control is started to the descending slope starting point p 2 a 400 to 500 m for example can be set on the basis of the flowchart in fig4 and also by referring to fig2 and 3 control of the fuel saving driving system 100 will be described in fig4 the control unit 10 reads the vehicle speed data step s 1 from the information from the.