the first poppet 32 that is in close contact with the body 17 of the control valve to serve as a damper when the branch flow path 7 a is blocked through mutual close contact between the first poppet 32 and the body 17 of the control valve the control valve system further includes a sealing o ring that prevents the hydraulic fluid from leaking to the outside through a gap of a close contact surface between the body 17 of the control valve and the flange 37 in this case a configuration of a control system for a construction machine in accordance with an embodiment of the present invention is the same as that of the hydraulic system shown in fig1 except the control valve 30 that is installed in a branch flow path 7 a and serves as a check valve and an orifice so as to prevent a single traveling of the machine during a combined operation in which a traveling operation and a working operation are performed simultaneously thus the detailed description of the same configuration and operation thereof will be omitted to avoid redundancy and the same elements are denoted by the same reference numerals hereinafter a use example of a traveling control system for a construction machine in accordance with an embodiment of the present invention will be described in detail with reference to the accompanying drawings as shown in fig3 a case of a combined operation in which an attachment such as an arm is driven during the traveling of the machine will.