A vehicle driving assist system calculates a risk potential indicative of a degree of convergence between a host vehicle and a preceding obstacle. Then, the system performs a driver notification operation that produces a driver notification stimulus based on the risk potential such as decreasing the driving force exerted against the vehicle as the risk potential increases and increasing an actuation reaction force exerted on the accelerator pedal during its operation as the risk potential increases. If a failure is detected in a reaction force generating device serving to add a reaction force to the accelerator pedal in accordance with the risk potential, then the system corrects an engine torque characteristic such that the engine torque does not increase even if the accelerator pedal is depressed to suppress an odd feeling in the vehicle performance by the driver when a failure occurs in the reaction force generating device.