Influence of Connected and Autonomous Vehicles on Traffic Flow Stability and Throughput

Influence of Connected and Autonomous Vehicles on Traffic Flow Stability and Throughput

Existing studies do not distinguish between connected and autonomous vehicles while examining their effects of the driving environment. This article conducts studies with distinguished vehicle types to establish a framework of several adoption scenarios to analyze the stability of the resulting traffic stream. The results demonstrated the ability of connected and autonomous vehicles to improve string stability. The study also found that automation was more effective at preventing shockwave formation and propagation. Under certain model scenarios, potential throughput also increased.

"The introduction of connected and autonomous vehicles will bring changes to the highway driving environment. Connected vehicle technology provides real-time information about the surrounding traffic condition and the traffic management center’s decisions. Such information is expected to improve drivers’ efficiency, response, and comfort while enhancing safety and mobility. Connected vehicle technology can also further increase efficiency and reliability of autonomous vehicles, though these vehicles could be operated solely with their on-board sensors, without communication. While several studies have examined the possible effects of connected and autonomous vehicles on the driving environment, most of the modeling approaches in the literature do not distinguish between connectivity and automation, leaving many questions unanswered regarding the implications of different contemplated deployment scenarios. There is need for a comprehensive acceleration framework that distinguishes between these two technologies while modeling the new connected environment. This study presents a framework that utilizes different models with technology-appropriate assumptions to simulate different vehicle types with distinct communication capabilities. The stability analysis of the resulting traffic stream behavior using this framework is presented for different market penetration rates of connected and autonomous vehicles. The analysis reveals that connected and autonomous vehicles can improve string stability. Moreover, automation is found to be more effective in preventing shockwave formation and propagation under the model’s assumptions. In addition to stability, the effects of these technologies on throughput are explored, suggesting substantial potential throughput increases under certain penetration scenarios."

Key findings

"The effects of connected and autonomous vehicles on throughput are investigated through a series of simulations. The simulation results revealed that scatter in fundamental diagrams increases as market penetration rate of connected/autonomous vehicles increases from 0% to 50% and decreases after this point. However, the throughput increases as market penetration rate increases."

"The analytical studies revealed that connected and autonomous vehicles can improve the string stability of traffic flow. Automation is likely to be more effective than connectivity alone in preventing shockwave formation and propagation, which is also confirmed by simulation results. Simulation results also revealed that oscillation and collision thresholds increase as platoon size decreases/market penetration rate increases."

"The simulation results also showed that autonomous vehicles result in higher throughput compare to connected vehicles at similar market penetration rates. Substantial potential throughput increases are possible under certain market penetration scenarios. Extending the acceleration framework to include driver’s anticipation is the subject of future research."

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