In a road traffic simulation apparatus that expresses a plurality of mobile units and road traffic environments on a computer to simulate traffic situations in association with a plurality of mobile units, each of the mobile units is expressed by a combination of a driver model, a model of driving operations of a virtual driver, and a vehicle dynamics model, a model of physical behaviors of a mobile unit. The mobile units are programmed to travel independently to each other in a road traffic environment that is expressed on the computer.