Abstract: This paper discusses the pressing need for the traffic contro1 of urban freeway. Incorporating the characteristics of urban expressway with a macroscopic dynamic deterministic traffic flow model, a variable speed limit control (VSLC) approach is proposed. The main idea is that we use a VSLC for middle-low traffic density section, and a VSLC, together with an on-ramp control, for middle-high traffic density section based on the principle of fuzzy logic. The VSL controller is used to regulate the velocity of vehicles and therefore, to make the traffic flow more stable, while the on-ramp controller is only used in middle-high traffic density section to maintain the density of the traffic flow on the mainline. The simulation results are also given to show the effectiveness of the proposed approach.

Key words: Urban expressway, Macroscopic traffic flow model, Fuzzy logic, Variable speed limit, On-ramp control

摘要： 首先阐述了城市快速路进行交通控制研究的迫切性，进而根据快速路各密度区的交通特点，结合宏观、动态、确定性交通流模型，提出了一种中低密度区采用可变限速控制、中高密度区采用可变限速结合入口匝道控制的交通流控制策略。依据此方案，分别设计了可变限速控制器和入口匝道控制器，前者用于调节车辆速度以确保车流稳定，后者仅用于中高密度区以维持主线车流密度。最后，对系统进行仿真并作了相应分析。

关键词: 城市快速路, 宏观交通流模型, 模糊逻辑, 可变限速, 入口匝道控制