Abstract: In this paper, a new concept of assignmentability is proposed. The concept is used to assess the efficacy of the dynamic traffic assignment on road networks and also used to be the principle of network time-space division of dynamic traffic assignment. The characteristics of traffic flows are researched not only on space but also on time. At last, the course of dynamic time-space division of traffic network is given. The study provides a rational object for dynamic traffic assignment modeling.

Key words: dynamic traffic assignment, assignmentability, the line-set saturation, time-space division