Study On The Impact Of Variable Message Sings (VMS) On Properties Of Traffic Flow Based On Cellular Automata Model

With the rapid development of economy and improved people's living condition, traffic demand has increased so much, followed by rapid increasing of vehicles on city roads, and traffic congestion has become one of the mian traffic problems, which severely obstruct urban development.To resovle traffic problems, not only the construction and maintenance but also efficient traffic management and controlling is important and essential,especially in the cities of high population. As one of the main measures of traffic management and controlling, urban traffic flow guidance system can ease traffic jam effectively. The technology of variable message signs (VMS) is widely used in urban traffic flow guidance system, and we studied the impact of variable message signs on the properties of traffic flow to give advices to relieve traffic congestion. Our work is organized as follows:1.For the irrationality of two-lane system researched before, a more practical two-lane system is proposed in this paper, and two modified message feedback strategies separately named mean spacheadway feedback strategy(MHFS) and mean time-headway feedback strategy(MTFS) are also proposed here. We will study the influence of modified strategies on traffic flow and compare it with that of two traditional feedback strategies, travel time feedback strategy (TTFS) and mean velocity feedback strategy (MVFS).Results of studies show that:under different entering probabilities and ratios of dynamic vehicles, the two modified feedback strategies could make traffic flow steady which couldn't be obtained by using TTFS and MVFS,and that proved the rationality and advantage of modified strategies.2.For the low utilization rate of roads caused by dedicated bus lane (DBL), bus lane with intermittent priority (BLIP) was studied in this paper and traffic model was builded using cellular automata model.To verify the advantages of BLIP, we compared the impact of bus lane with intermittent priority (BLIP) on traffic flow with that of dedicated bus lane (DBL).Researching results indicated that adapting BLIP could improve flux and increase the utilization rate of roads.Besides, that how to set VMS properly to make bus lane sufficiently used and make no delay of buses ws also studied here, finally the optimal interval between adjacent VMSs was given.3.Sudden accidents always cause severe traffic jam on city roads, and how to ease traffic jam has become an important subject. In this paper we used a method of setting VMS to improve the driving condition of a two-lane road with an accident. Cellular automata model was also used here to build traffic model.Simulating results made it clear that our method could alleviate the jam caused by accident and increase flux.The impact of entering probability, ratio of slow cars and severity of accident on properties of traffic flow are investigated before and after setting VMS.