A Numerical Study on Constant Spacing Policies for Starting Platoons at Oversaturated Intersections

Abstract

Cooperative Adaptive Cruise Control (CACC) is considered as a key potential enabler to improve driving safety and traffic efficiency. It allows for automated vehicle following using wireless communication in addition to onboard sensors. To achieve string stability in CACC platoons, constant time gap (CTG) spacing policies have prevailed in research; namely, vehicle interspacing grows with the speed. While constant distance gap (CDG) spacing policies provide superior potential to increase traffic capacity than CTG, their major drawbacks are a smaller safety margin at high velocities and that string stability cannot be achieved using a one-vehicle look-ahead communication. In this work, we propose to apply CDG only in a few driving situations, when traffic throughput is of highest importance and safety requirements can be met due to relatively low velocities. As the most relevant situations where CDG could be applied, we identify starting platoons at signalized intersections. With this application scenario we show that applying CDG only in a few specific and crucial situation can have a major impact on traffic efficiency. Specifically, we compare CTG with CDG regarding its potential to increase the capacity of traffic lights. Starting with the elementary situation of single traffic lights we expand our scope to whole traffic networks including several thousand vehicles in simulation. Using real world data to calibrate and validate vehicle dynamics simulation and traffic simulation, the study discusses the most relevant working parameters of CDG, CTG, and the traffic system in which both are applied.

Impacts of Platooning of Connected Automated Vehicles on Highways

“…Over the years, policies based on temporal gaps have gained acceptance, as they are associated with greater platoon stability [14], as described in Section IX. Alternatively, some authors choose to combine them with policies based on spatial gaps, which are reported to favor the increase of capacity (e.g., [15]).…”

“…Reference [15] focused on platoons of CACC vehicles. Their aim was to show that the combination of different car-following policies (i.e., space-based and time-based) would allow maximizing traffic capacity, while preserving safety and stability.…”

“…When platoons become unstable, in addition to dangerous situations, they also cause inefficiencies in terms of flow and energy consumption. Because it is easier for a platoon to become string unstable if vehicles circulate at very small distances, it seems increasingly clear that there is a need to move towards adaptive carfollowing policies, at least in terms of the values of the key parameters, namely space or time gaps ( [15], [18], [32]). The same reflection applies to the maximum allowable platoon length, which on average should not surpass 5-6 vehicles ( [14], [17], [48]).…”

Real-time response control oriented method for discriminating the headway property of unsaturated headways at green light release

“…In recent years, many scholars have conducted researches on unsaturated headway, The headway time distance distribution of downstream vehicles at signal intersections has been studied by Zhengdao Ding [1] , Changqiao Shao [2] , Aizeng Li [3] , Huiying Wen [4] and various fitting models have been established; Fujian Wang [5] by comparing the fitting accuracy of headway time distance distribution models, the proposed mixed headway time distance distribution model based on multi-class following behavior outperformed the Weibull distribution and lognormal distribution model; Yong Qian [6] based on the distribution law of headway time distance, a signal timing algorithm without the total lost time as a variable is discussed, and an optimal green light time control optimization method based on the headway time distance distribution and queue length is proposed; Yun Xing [7] proposed a threshold division method considering randomness, mainly including the determination of the starting point of unsaturated traffic flow calculation and the selection of division threshold; Jiaqi Li [8] and Dianhua Cheng [9] proposed a fuzzy traffic flow control scheme based on the green light time correction algorithm of headway time distance for urban intersections respectively.J Chen [10] , Xiaopeng Li [11] and Kay Massow [12] Combines the determination of headway at intersections with vehicle networking and autonomous driving.Cesme B [13] and Furth P G [14] explores a new paradigm for traffic signal control based on local actuated control but with some additional rules that create coordination mechanisms, and the simulation proved that the study had little impact on traffic delays.…”