Abstract
Ramp metering on freeway is one of the effective methods to alleviate traffic congestion. This paper advances the field of freeway ramp metering by introducing an application to the on-ramp, capitalizing on the macro traffic follow theory and improved the freeway traffic flow. The Particle Swarm Optimization (PSO) based on Proportional Integral Derivative (PID) controller is further developed to single ramp metering as well as to optimize the PID parameters. The approach is applied to a case study of the Changyi Freeway(G5513) in Hunan, China. The simulation is conducted by applying the actual profile traffic data to PID controller to adjust the entering traffic flow on the freeway on-ramp. The results show that the PSO-PID controller tends to converge in about 80 minutes, and the density tends to be stable after 240 iterations. The system has smaller oscillation, more accurate adjustment of ramp regulation rate, and more ideal expected traffic flow density. The traffic congestion on mainline is effectively slowed down, traffic efficiency is improved, and travel time and cost are reduced. The nonlinear processing ability of PSO-PID controller overcomes the defects of the traditional manual closing ramp, and can be successfully applied in the field of intelligent ramp metering.
Highlights
The aim of freeway on-ramp metering is to control the traffic demand
The simulation result of density variation under Particle Swarm Optimization (PSO)-Proportional Integral Derivative (PID) control based on MATLAB platform is shown in Fig 6 with the same data and parameters in Fig 4, which gives the density variation of downstream section under PSO-PID control
By learning from PSO algorithm, the PID parameters are changing in real time, which reflects the significance of intelligent traffic management in freeway ramp metering
Summary
The aim of freeway on-ramp metering is to control the traffic demand. According to the traffic state of the main line, the ramp entering rate can be adjusted to support the traffic flow distribution of main line more regular, and the traffic capacity can be maximized. Most of the time in China, the treatment of freeway congestion is to close the ramp through traffic control, and the closing time is usually very long. Ramp closure will affect journeys for travelers, and may trigger accidents. Relying on the observation and feedback of the road operation state and closing the ramp cannot completely solve the problem of freeway congestion. It is necessary to develop the intelligent control of freeway ramp metering
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