Evaluating the Safety of Platooned Heavy Vehicles: A Case Study (original) (raw)
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European Transport \ Trasporti Europei, 2020
The study aims to investigate the impact of heavy vehicles (HVs) on traffic characteristics under platoon conditions on Indian highways. Traffic volume, speed, and time headway data were gathered from different highway sections using infra-red sensors. The mean relative speed criteria were used as an indicator of variability to estimate the critical time headway. The threshold value of a critical time headway of 4 sec was determined to represent vehicles into non-platoon followers and platoon followers. The speed-flowdensity model curves were developed for two different traffic regimes, one without platoons and the other with platoons created by the HVs. The results show that under platoon conditions, the speed at capacity, density at capacity, and traffic capacity reduced by 11.2%, 12.5%, and 22.3%, respectively, compared to non-platoon conditions. Additionally, the average travel time and travel delay increased by 18.1 s/km and 12.7 s/km, respectively. The study's findings emphasize the importance of considering platoon dynamics under the influence of HVs to better understand their impact on traffic characteristics.
Longitudinal Safety Evaluation of Connected Vehicles' Platooning on Expressways
2018
Connected vehicles (CV) technology has recently drawn an increasing attention from governments, vehicle manufacturers, and researchers. One of the biggest issues facing CVs popularization associates it with the market penetration rate (MPR). The full market penetration of CVs might not be accomplished recently. Therefore, traffic flow will likely be composed of a mixture of conventional vehicles and CVs. In this context, the study of CV MPR is worthwhile in the CV transition period. The overarching goal of this study was to evaluate longitudinal safety of CV platoons by comparing the implementation of managed-lane CV platoons and all lanes CV platoons (with same MPR) over non-CV scenario. This study applied the CV concept on a congested expressway (SR408) in Florida to improve traffic safety. The Intelligent Driver Model (IDM) along with the platooning concept were used to regulate the driving behavior of CV platoons with an assumption that the CVs would follow this behavior in real-world. A high-level control algorithm of CVs in a managed-lane was proposed in order to form platoons with three joining strategies: rear join, front join, and cut-in joint. Five surrogate safety measures, standard deviation of speed, time exposed time-to-collision (TET), time integrated time-to-collision (TIT), time exposed rear-end crash risk index (TERCRI), and sideswipe crash risk (SSCR) were utilized as indicators for safety evaluation. The results showed that both CV approaches (i.e., managed-lane CV platoons, and all lanes CV platoons) significantly improved the longitudinal safety in the studied expressway compared to the non-CV scenario. In terms of surrogate safety measures, the managed-lane CV platoons significantly outperformed all lanes CV platoons with the same MPR. Different time-to-collision (TTC) thresholds were also tested and showed similar results on traffic safety. Results of this study provide useful insight for the management of CV MPR as managed-lane CV platoons.
International Journal of Intelligent Transportation Systems Research, Springer, 2021
Heavy-Duty Vehicles (HDVs) on highways are among the major passengers and freight traffic carriers that occupy any space available on the roadway. The movement of HDVs under the mixed traffic environment causes higher levels of interaction between vehicles due to their physical and operational characteristics. Besides, the HDVs operating at less than their desired speed on the highway lanes cause a mixed traffic platoon formation. The primary purpose of the study is to investigate the impact of multi-class HDVs on the speed and flow rates of each highway lane under platooning conditions. In this study, traffic data was collected using an Infra-Red (IR) sensor-based device at six highway sections in India. The simultaneous equations approach is used to model the traffic speeds for determining the Dynamic Passenger Car Unit (DPCU). The speedflow plots are established for Median Lane (ML) and Kerb Lane (KL), a minute before the arrival of HDVs (state A) and a minute after the arrival of HDVs (state B) at the IR sensor detection point, to quantify the impacts of HDVs on the speed and traffic flow rate. The study findings reveal that the speed and flow in ML and KL reduce significantly due to the influence of multi-class HDVs in the general traffic mix. Also, the speed and flow rate in ML and KL decreased with an increase in the percentage of multi-class HDVs. However, this effect was found to be comparatively higher in the ML than that in the KL. Finally, this study sets out recommendations to mitigate the adverse impacts of multi-class HDVs on the highways to enhance the speed and flow rate.
Experimental Survey and Modeling for the Driver Behavior in Vehicle Platoons
Procedia - Social and Behavioral Sciences, 2014
The objective of this paper is study the driver behaviors in the vehicle platoons starting from a traffic light. This study i s necessary to model the changes in the shape of the vehicle platoons at different sections along the road. It is need to understand these changes in order to define an adequate programming of the traffic light phases. The study started from a survey of traffic flows on a road section of about 650 m.: all vehicles have been followed from the start section and for each of them were recorded the transit times on next sections at known distance. The data have been analyzed with two different methods: Cyclic Flow Profiles and the Weibull distribution. The calibrated CFP, with correct parameter values, well represent the trend and the dispersion of vehicle platoons at the observed road section. The Weibull distribution, basic used to describe life-time reliability characteristics in model failure testing, can be a powerful tool also for the prediction of vehicle platoons on the road sections. Fact, starting from the flow study in a number of sections, it is possible to know the trend of distribution parameters as function of the start distance. The variation of two parameters along the road from the first section (first signal light) appears to be linear for the first parameter (position), almost linear for the second (form).
Transportation Research Record: Journal of the Transportation Research Board
Truck platooning is the application of cooperative adaptive cruise control where multiple trucks are electronically linked using vehicle-to-vehicle communication. Although truck platoons might bring fuel savings and emission reductions, their interactions with surrounding traffic and resulting impact on traffic operations and safety are not fully understood. The objective of this paper is to evaluate traffic efficiency and safety in a critical traffic situation when truck platoons are introduced in the system. This paper presents a case study of a merging section, located on A15 motorway, near the port of Rotterdam in the Netherlands. We consider two scenarios: platoons on a mainline carriageway and platoons merging onto a mainline carriageway. We simulate the movements of truck platoons in a microscopic traffic simulator. Longitudinal and lateral controllers for truck platoons, proposed in this paper, can ensure their collision-free, string-stable, and smooth driving behavior. Simu...
A General Simulation Framework for Modeling and Analysis of Heavy-Duty Vehicle Platooning
IEEE Transactions on Intelligent Transportation Systems, 2016
—Platooning heavy-duty vehicles (HDVs) on a highway is a method for improving energy and transport efficiency. On one hand, HDV platoon driving in small intervehicle distances could increase highway capacity; on the other hand, HDVs traveling in small intervehicle distances experience significant air-drag reduction and, therefore, improve fuel efficiency. However, although the majority of research has been conducted on the development of platoon systems, very few studies have focused on quantification of the impacts of HDV platooning on traffic flow. This paper initializes a simulation framework to facilitate the study of HDV platooning and establishes the corresponding concept and operations. The longitudinal driving behaviors of HDV platoons are modeled in detail, considering the acceleration capability of an HDV. The proposed framework is applied on three experimental cases: the first case is to study the impacts of HDV platooning on traffic flow and the second and third cases are about the influence of traffic on HDV platoon formation. In the first case, simulation outcomes show that the increasing percentage of HDV platooning in traffic flow generally results in more dramatic improvements on traffic efficiency, while preserving traffic safety for passenger vehicles. In the second and third cases, for the HDV platoon formation, deceleration of the first HDV to a low speed during platoon formation will increase the formation time to a large extent in medium and heavy traffic. Index Terms—HDV platoon, ACC/CACC system, asymptotic stability, HDV platoon formation.
Transportation Research Part C: Emerging Technologies, 2021
In the foreseeable future, connected vehicles (CVs) will coexist with traditional vehicles (TVs) resulting in a complex mixed traffic environment and the success of CVs will depend on the characteristics of this mixed traffic. Therefore, before the large scale deployment of CVs, it is important to examine how CVs will influence the characteristics of the resultant mixed traffic. To achieve this aim, this study models the mixed traffic of TVs and CVs, and examines the traffic flow disturbance, efficiency, and safety. Intelligent Driver Model (IDM) with estimation errors is utilised to model TVs since it incorporates human factors such as estimation errors. Whereas, connected vehicle driving strategy integrated with IDM is utilised to model CVs because it incorporates driver compliance, a critical human factor for the success of CVs. Moreover, two classes of drivers based on their compliance levels are considered, namely the high-compliance drivers and the low-compliance drivers, to comprehensively investigate the impact of driver compliance on the mixed traffic of CVs and TVs. Two simulation experiments are performed in this study. The first experiment is used to measure traffic flow disturbance and safety while the second is used to measure the traffic flow efficiency. Furthermore, a total of 7 mixed traffic environments are generated in each experiment via different combinations of TVs, CVs with low compliance drivers, and CVs with high compliance drivers. Another important point considered in the simulation is the spatially distribution of CVs in the platoon. As such, three platoon policies are investigated. In the first policy i.e., the best case, the CVs are spatially arranged with a motive to maximise benefits from CVs whereas in the second policy i.e., the worst case, the CVs are spatially arranged with a motive to minimise benefits from CVs. Finally, in the third platoon policy i.e., the random case, the CVs are distributed randomly in the platoon. This study demonstrates the importance of the spatial arrangement of CVs in a platoon at a given penetration rate and its impact on traffic flow disturbance, efficiency, and safety. Moreover, findings from this study underscores that CVs can supress the traffic flow disturbance, and enhance traffic flow efficiency, and safety; however, traffic
Scenario-Based Simulation Studies on Platooning Effects in Traffic
Energy-Efficient and Semi-automated Truck Platooning
This chapter outlines the portfolio of simulation campaigns that have been carried out to thoroughly study the effects of platooning in the traffic system. The approach outlined in Chap. 10.1007/978-3-030-88682-0_7 is utilised to quantify typical platoon trajectories and manoeuvres in highway settings as well as in urban intersection scenarios. The addressed studies do not yield a single result, but instead depend on many parameters (such as platoon spacing/gap policy, surrounding traffic density and speed and many more) and are investigated in terms of the results’ sensitivities on these parameters. This approach allows one to draw meaningful conclusions despite the inherent uncertainty and spread of the influencing parameters. By using representative conditions, the resulting KPI distributions are evaluated and interpreted. Considering real traffic parameters, such as density, truck share, distances, speed and their empirical distributions and restrictions on the assumed “degree o...