This paper reviews and compares car-following and lane- changing logics embedded in some microscopic traffic simulation models, and comments are made on the existing techniques of traffic simulation. Future directions of traffic simulation are identified in three aspects: vehicle modeling, driver modeling, and vehicle movement modeling. To illustrate these ideas, a conceptual model, 2DSIM, is proposed, which consists of a dynamic vehicle sub-model and an intelligent driver sub-model. They are further integrated into a driver-vehicle-environment closed-loop system which constitutes the basic building block of road traffic.