The real-time signal control problem of traffic intersections is studied, and a multi-stage decision model is
proposed to minimize the waiting time. The model takes advantages of the structure of the minimum green and red time,
which significantly reduces the model scale by properly choosing the system states and control actions. Additionally, a
forward dynamic programming algorithm is developed, which can efficiently obtain the optimal solutions. Numerical results
show that the waiting time can be reduced in comparison with the fixed-time periodic control policy, and computation time
can be saved in comparison with the mixed integer programming, which can satisfy the real-time control requirement.