Abstract
An integrated control strategy is considered in this paper with the aim of solving congestion in freeway merging regions during peak hours. Merging regions discussed in this paper include the mainline and on-ramp. Traditional research mainly focuses on the efficiency of traffic, ignoring the experience of on-ramp drivers and passengers. Accordingly, a dynamic competition control strategy is proposed to balance individual behaviour and traffic efficiency. First, the concept of the congestion index is introduced, which is expressed by the queue length and the speed parameter of the merging region. The congestion index is used to balance the priorities of the vehicles from the mainline and on-ramp into the merging region in order to avoid poor individual behaviour of on-ramp drivers due to the long-time waiting. Additionally, a nonlinear optimal control approach integrating variable speed limits control and ramp metering is proposed to minimize the total time spent and the maximum traffic flow. The integrated control approach proposed in this paper is tested by simulation which is calibrated using field data. The results indicate that the integrated control approach can effectively shorten the total delay and enhance the traffic service level.
Highlights
Congestion in freeway networks has been recognized as a common issue
The main contributions are presented as follows: –– A dynamic competition control strategy is considered in this paper, which can balance the relationship between individual behaviour and traffic efficiency in the merging region of freeway networks. –– Queue, as a significant parameter of the principle of distribution of rights, is derived based on the nonlinear macroscopic traffic flow model. –– A nonlinear optimal control approach, integrating the mainline Variable Speed Limits control and on-ramp control, is proposed through the derivation of the model with the consideration of the dynamic competition control strategy
Taking into account the mainstream traffic speed decrease caused by on-ramp traffic flowing into the merging region, the adjustment coefficient becomes dDtq0 ^k hvm,1 ^k h Lm mm ^ tm,1 ^k h + lh where δ is defined as a constant parameter, which is computed based on the field data; q0(k) is the traffic flow coming from the upstream of link m; vm,1(k) is the traffic speed of the first segment of link m; κ is global constant parameter which is achieved by a series of parameters, which is used for depicting the characteristic of the traffic system
Summary
Congestion in freeway networks has been recognized as a common issue. In general, the issue of traffic congestion can be solved by changing linear structure of the road or adopting traffic management measures. Emphasize the homogenization of traffic speeds [810]; (b) focus on the prevention of freeway traffic breakdown [11, 12]; and (c) limit the flows in the control region [13] Such VSL control approaches can improve the quality of service, applying VSL control to the upstream mainline of the merging region only is insufficient to get reliable results when congestion occurs in the ramp merging region [14]. The main contributions are presented as follows: –– A dynamic competition control strategy is considered in this paper, which can balance the relationship between individual behaviour and traffic efficiency in the merging region of freeway networks. –– A nonlinear optimal control approach, integrating the mainline Variable Speed Limits control and on-ramp control, is proposed through the derivation of the model with the consideration of the dynamic competition control strategy.
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