Investigations And Applications Of Information Feedback Mechanism In Intelligent Transportation Systems

The comprehensive capacity of transportation system is a key index to mea-sure the prosperity of a country. Not only is it crucial to the national economic development, but it also determines the modernizing progress of a country. There-fore, governments of various countries are encouraging scientists to develop the new types of traffic systems. Under this background, intelligent transportation system has come into being. In recent years, information feedback strategy serving as the critical part of intelligent transportation system has been treated with ever-increasing emphasis. Since Wahleet al. proposed the first information feedback strategy in2000, a dozen of them have been introduced after more than a decade. On the basis of previous study, my contribution in this field is to design various feedback strategies based on real-time traffic information and road structures. The research works are specified as follows:1. In the light of the characteristics of asymmetrical two-route scenario with bottleneck and one exit, we designed the piecewise function feedback strategy. Be-sides that the new strategy can distinguish the weight of congestion clusters when they are in different positions on the road, it even gives out the distinction weight of clusters whether they are in the bottleneck or not. Combined with the travel time feedback strategy, mean velocity feedback strategy, congestion coefficient feedback strategy and weighted congestion coefficient feedback strategy raised by former re-searchers, we apply these four strategies into the asymmetrical two-route scenario with bottleneck and one exit for simulation. The simulation results suggest that piecewise function feedback strategy is the optimal one among all the feedback strategies. It outperforms others in terms of the stability of the traffic flux, average speed and vehicle density, and also exceeds others for the value of average flow.2. Built on the design principles of weighted information feedback strategies, a new strategy is proposed, namely the exponential function feedback strategy. After analyzing two previous strategies, we find the reason why corresponding angle feedback strategy is superior to weighted congestion coefficient feedback strategy. Given that the sharp decay of the weighted coefficient is the key point, we propose the exponential function feedback strategy. This new strategy together with three other strategies related to the congestion coefficient are all applied into two kinds of one dimensional road model for simulation. The simulation results show that compared with other strategies, exponential function feedback strategy has distinct advantages in vehicle number and flux. Although the advantage of the average flow of the new strategy is not obvious at the side of the corresponding angle feedback strategy, the exponential function feedback strategy is applicable to more complex models and relatively convenient to employ. According to the simulation results, we even find that the exponential function feedback strategy and the corresponding angle feedback strategy are unsuited to be applied into the closed transportation systems. This conclusion will be came to again by the following research.3. The application of feedback strategies in the two-dimensional road model. In this section, three different states, critical density as well as the distribution of vehicles are discussed in detail when the randomized choosing route strategy, expo-nential function feedback strategy, mean velocity feedback strategy and congestion coefficient feedback strategy are applied into the two-dimensional road model. The results display that the critical density of the mean velocity feedback strategy and congestion coefficient feedback strategy are higher than that of other two strategies. Next, the effect of the traffic light period and the traffic light rules are investigated. The results indicate that with increasing the traffic light period, its influence on the systems decreases. As the density is in the interval of saturation state, adopting the congestion coefficient feedback strategy with the anticlockwise traffic light rule will be more conducive to improve the transportation capability. In addition, we also study the effect of the route length and the side length of the traffic network. We concluded that in the highly symmetric network, equably feeding back the traffic information will help to improve the traffic flow.4. On the basis of two-dimensional road model, a feedback strategy based on global information to search the minimum weighted path is introduced, called the route weighted by travel time feedback strategy. This new strategy can not only enhance the traffic flow, but have the vehicle evenly distributed as well.5. Acting on the definition of traffic flux, we present the space flux feed-back strategy and time flux feedback strategy and explain the regulations of them. This two strategies together with congestion coefficient feedback strategy, predic- tion information feedback strategy and vehicle number feedback strategy as well as weighted congestion coefficient feedback strategy are applied into the symmetrical two-route model. And then, we obtain the simulations of the changing of vehicle number and flux according to time together with that of average flow according to the ration of dynamic vehicles. The results show that space flux feedback strategy enjoys great superiority over other strategies in terms of the average flow. With respect to other quantities such as the stability of vehicle number and flux, the new strategy is not inferior. Moreover, we applied these strategies into the symmetrical three-route model and asymmetrical two-route model with two exits. The results again demonstrate the superiority of space flux feedback strategy.6. Depending on the local traffic information, we present the vacancy length feedback strategy which united with nine previous strategies are all applied in the symmetrical two-route scenario with two exits and the asymmetrical two-route sce-nario with one exit. The simulation results turn out that the superiority of the feedback strategies based on the local information over the ones based on the global information and the vacancy length feedback strategy is the best one among all the feedback strategies based on the local information in terms of both the improving capacity of transportation systems and convenience of its application. Finally, we conclusion that in the open traffic systems the further the vehicle is away from the entrance, the less influence its condition imposes on the traffic capability. In order to improve the capability, the information of the entrance only need to be considered.In the end of this thesis, we summarized our research works and propose the outlook of future research.