Traffic impacts of commercial Adaptive Cruise Control time-gap policy

2021 ◽  
Author(s):  
Konstantinos Mattas ◽  
Giovanni Albano ◽  
Biagio Ciuffo
Keyword(s):  
Adaptive Cruise Control ◽  
Cruise Control ◽  
Control Time ◽  
Traffic Impacts ◽  
Time Gap

Should Adaptive Cruise Control (ACC) Systems Be Designed to Maintain a Constant Time-Gap Between Vehicles?

2001 ◽  
Author(s):  
Junmin Wang ◽  
Rajesh Rajamani
Keyword(s):  
Boundary Conditions ◽  
Traffic Flow ◽  
Adaptive Cruise Control ◽  
Constant Time ◽  
Cruise Control ◽  
Unconditionally Stable ◽  
Time Gap ◽  
Traffic Flow Stability ◽  
The Stability ◽  
Gap Spacing

Abstract This paper addresses the stability of traffic flow on a highway when the vehicles operate under an adaptive cruise control (ACC) system. ACC systems are commonly designed to maintain a constant time-gap between vehicles during vehicle following. Previous researchers in literature have produced contradictory results on whether the traffic flow is stable when the constant time gap spacing policy is used. This paper resolves the contradiction and shows that the boundary conditions used at the inlets and exits influence traffic flow stability in the case of the constant time-gap policy. Further, the paper shows that it is possible to design an unconditionally stable spacing policy, i.e. a spacing policy which guarantees traffic stability under all boundary conditions. The practical implications of instability are shown through traffic simulation results. The advantages of an unconditionally stable spacing policy over the constant time-gap policy are demonstrated. The answer to the question “Should ACC systems be designed to maintain a constant time gap between vehicles?” is NO. It is quite easy to develop alternate spacing policies with superior stability properties.

scholarly journals Drivers’ Interaction with Adaptive Cruise Control on Dry and Snowy Roads with Various Tire-Road Grip Potentials

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Ioana Koglbauer ◽  
Jürgen Holzinger ◽  
Arno Eichberger ◽  
Cornelia Lex
Keyword(s):  
Control Strategy ◽  
Adaptive Cruise Control ◽  
Driving Simulator ◽  
Mental Workload ◽  
User Acceptance ◽  
Cruise Control ◽  
Emergency Situations ◽  
Human Driver ◽  
Time Gap

This study investigates drivers’ interaction with Adaptive Cruise Control (ACC) in different road conditions and identifies areas of improvement. Ninety-six drivers drove with the ACC in a driving simulator showing either a summer scenery and a dry road with high grip potential or a winter scenery with a snowy road and reduced grip potential. The results show that on snowy roads the drivers set in average a lower ACC speed and preferred a larger ACC time gap. Drivers’ workload and effort were higher when using the ACC on snowy as compared to dry roads. Generally, the use of a shorter ACC gap resulted in lower ratings of comfort, safety, and trust and higher ratings of mental workload and effort in both dry and snowy road conditions. The drivers judged that ACC was braking too late and maintained a too short gap to the forward vehicle, especially when the ACC was set to 1 second as compared to a 1.8-second time gap. A future adaptation of ACC’s control strategy to reduced tire-road grip potential would not only improve comfort and user acceptance of the human driver but also increase the potential to react in emergency situations with braking or evasive steering.

scholarly journals Control Design, Stability Analysis, and Traffic Flow Implications for Cooperative Adaptive Cruise Control Systems with Compensation of Communication Delay

2020 ◽  
Vol 2674 (8) ◽  
pp. 638-652
Author(s):  
Yu Zhang ◽  
Yu Bai ◽  
Jia Hu ◽  
Meng Wang
Keyword(s):  
Traffic Flow ◽  
Local Stability ◽  
Adaptive Cruise Control ◽  
Control Design ◽  
Communication Delay ◽  
Cruise Control ◽  
String Stability ◽  
Cooperative Adaptive Cruise Control ◽  
Time Gap ◽  
Traffic Flow Stability

Communication delay is detrimental to the performance of cooperative adaptive cruise control (CACC) systems. In this paper, we incorporate communication delay explicitly into control design and propose a delay-compensating CACC. In this new CACC system, the semi-constant time gap (Semi-CTG) policy, which is modified on the basis of the widely-used CTG policy, is employed by a linear feedback control law to regulate the spacing error. The semi-CTG policy uses historical information of the predecessor instead of its current information. By doing so, communication delay is fully compensated, which leads to better stability performance. Three stability properties—local stability, string stability, and traffic flow stability—are analyzed. The local stability and string stability of the proposed CACC system are guaranteed with the desired time gap as small as the communication delay. Both theoretical analysis and simulation results show that the delay-compensating CACC has better string stability and traffic flow stability than the widely-used CACC system. Furthermore, the proposed CACC system also shows the potential for improving traffic throughput and fuel efficiency. Robustness of the proposed system against uncertainties of sensor delay and vehicle dynamics is also verified with simulation.

scholarly journals Development of simulation tests in ACC system scenarios for a car simulator station

2018 ◽  
Vol 19 (4) ◽  
pp. 75-81
Author(s):  
Mateusz Papis ◽  
Dominik Jastrzębski ◽  
Marcin Mirosław ◽  
Antoni Kopyt ◽  
Tomasz Dziewiński ◽  
...  
Keyword(s):  
Control System ◽  
Adaptive Cruise Control ◽  
Driving Simulation ◽  
Driver Model ◽  
Cruise Control ◽  
Adaptive Cruise Control System ◽  
Cruise Control System ◽  
Time Gap ◽  
Selection Of

This paper presents development of simulation tests for a driving simulation station in ACC (Adaptive Cruise Control) system scenarios. Experiment assumptions, simulation tests procedures, selection of the tested group, analyzed parameters and the results of the preliminary tests were discussed. The comparison between ride parameters of volunteers and a car equipped with ACC system and validation of previously created fuzzy-driver model are main aims of the study. The experiment, composed with two exercises (outside urban and mixed scenarios) will be performed on previously identified tested group of volunteers. Ride parameters, such as velocity, distance to a leading car, time gap, will be assessed according to a prepared procedure.

scholarly journals Effect of Adaptive Cruise Control on Mixed Traffic Flow: A Comparison of Constant Time Gap Policy with Variable Time Gap Policy

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jiakuan Dong ◽  
Jiangfeng Wang ◽  
Lei Chen ◽  
Zhijun Gao ◽  
Dongyu Luo
Keyword(s):  
Traffic Flow ◽  
Adaptive Cruise Control ◽  
Constant Time ◽  
Mixed Traffic ◽  
Cruise Control ◽  
Mixed Traffic Flow ◽  
Variable Time ◽  
Low Level ◽  
Time Gap ◽  
Simulation Results

With the emerging application of low-level driving automation technology, heterogeneous traffic flow mixed with human-driven vehicles and low-level autonomous vehicles is dawning. In this context, it is imperative to investigate its effect on mixed traffic flow. As a key component for adaptive cruise control (ACC) which is a practical low-level application of driving automation, the time gap policy determines the dynamic of ACC-equipped vehicles and plays a crucial role in traffic flow stability and efficiency. There are two main time gap policies used for ACC at present, namely, constant time gap (CTG) policy and variable time gap (VTG) policy. In this study, we carried out a detailed comparison between these time gap policies to investigate their potential effect on mixed traffic flow, where the analytical- and simulation-based approaches are both considered. Analytical results show that VTG policy is superior to CTG policy in stabilizing the mixed traffic flow. In addition, numerical simulations are also conducted and simulation results further support the analytical results. As for throughput, there is no difference between CTG policy and VTG policy in analytical progress when the same time gap is set at the equilibrium. However, simulation results based on an on-ramp scenario show that the throughput of mixed traffic flow with VTG policy is slightly higher than that of CTG policy. Meanwhile, the scatter of mixed traffic flow with VTG policy in the flow-density diagram gradually clusters in the middle range of density (i.e., 20–40 veh/km) with the increase of the penetration rates of ACC vehicles, where the traffic flow operates more efficiently. These results indicate that VTG policy is better than CTG policy when designing controllers for ACC in the context of traffic flow operation and control.

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