Abstarct: Using driver assistant systems in vehicles to reduce the driver's workload and consequently reduce driver fatigue is increasingly expanding. Among these systems, adaptive cruise control systems, with the ability to automatic control of longitudinal dynamics, have great importance place. By this automation, the role of driver changes from operator to supervisor. It should be noted that the adaptive cruise control can be affect on traffic flows, reduction vehicle fuel consumption and enhanced driver safety intensity and have better performance than human driver. In this study, a passenger car that is moving on the highway and city traffic, will be examined. Longitudinal dynamics equations of the vehicle including resisting forces will be brought and uncertainties in the model will be discussed. To control the speed of vehicles on the highway and vehicle distance control in city traffic, vehicle longitudinal control laws have been proposed. From sliding mode method which is a robust control method for control nonlinear systems is used for design controller. The controller includes two control algorithms: the speed and distance control and Duty of controllers is force generation needed to move the vehicle and overcome the disturbances and uncertainty that by tracing it by car, the vehicle speed control is done. Finally, the proposed controls rules were applied to vehicle dynamics equation and to ensure the ability of control and efficiency under different conditions, the simulation was conducted. The simulation results show that the designed controller is robust against structured and unstructured uncertainty and well managed track the driver's desired speed and desired distance in different load conditions such as changes of rolling resistance force, severe wind and changes in vehicle weight, with acceptable accuracy.