The traffic guidance system is an important subsystem in the intelligent transportation system which can timely release alerts regarding traffic congestion, incidents and other information to road-users. However, it is very hard to decide the releasing range exactly where and for whom to release such information. With the correlation analysis of road traffic flow in time and space domain, the releasing range model for traffic guidance information is formulated based on combinatorial mathematics in this paper. As it is difficult to get the optimal solution in a limited time through analysis for the model, a simple greedy algorithm, an algorithm based on simulated annealing and an algorithm based on M-Chameleon clustering are presented to divide the road links into several groups. Some traffic flow data detected by remote microwave sensors in some road links in Beijing urban expressway are employed to compare the algorithms. The results show that the algorithm based on M-Chameleon achieved the best performance, and it can be used to improve the pertinence, validity and automation of releasing traffic guide information.