Queue Length Estimation and Platoon Recognition Using Connected Vehicle Technology for Adaptive Signal Control

This dissertation presents mathematical and analytical models for real-time queue length estimation and platoon recognition using the connected vehicle technology (CVT). Information on queue length and platoon is a crucial part of traffic signal control and is difficult to obtain accurately with traditional technologies such as loop detectors. The past studies are either limited to fixed-time signal control or lacked verification on the applicable range or evaluation of the performance of algorithms. The proposed algorithms focused on estimating the queue length for adaptive signal control and platoon characteristics for signal coordination and adaptive signal control. For queue length detection, an algorithm was developed to determine the estimated value between the last stopped vehicle and the first moving vehicle for different market penetration ratios. Discrete wavelet transform is applied to the estimated queue lengths to improve accuracy and consistency. The platoon recognition model is developed based on time headway so that the arrival times can be computed directly from the estimated platoon data. First, the detected platoon is identified by a modified critical time-headway. Then, platoon size and starting and ending times are estimated. Lastly, a filtering process for “qualified” detected platoon is proposed to optimize detectability. The results show that the proposed algorithms can estimate well in various traffic conditions and under both fixed-time and actuated signal control without relying on inputs that are hard to obtain in practice. Furthermore, an analytical model to estimate the platoon detection rate is proposed and shown to be close to the numerical results. Therefore, Traffic engineers can use the analytical model to estimate the required market penetration ratio for the application without field experiments or microscopic simulation. Accordingly, the proposed algorithms can be an important part of adaptive signal control focusing on real-time coordination

Exploring Smart Infrastructure Concepts to Improve the Reliability and Functionality of Safety Oriented Connected Vehicle Applications

Cooperative adaptive cruise control (CACC), a form of vehicle platooning, is a well known connected vehicle application. It extends adaptive cruise control (ACC) by incorporating vehicle-to-vehicle communications. A vehicle periodically broadcasts a small message that includes in the least a unique vehicle identifier, its current geo-location, speed, and acceleration. A vehicle might pay attention to the message stream of only the car ahead. While CACC is under intense study by the academic community, the vast majority of the relevant published literature has been limited to theoretical studies that make many simplifying assumptions. The research presented in this dissertation has been motivated by our observation that there is limited understanding of how platoons actually work under a range of realistic operating conditions. Our research includes a performance study of V2V communications based on actual V2V radios supplemented by simulation. These results are in turn applied to the analysis of CACC. In order to understand a platoon at scale, we resort to simulations and analysis using the ns3 simulator. Assessment criteria includes network reliability measures as well as application oriented measures. Network assessment involves latency and first and second order loss dynamics. CACC performance is based on stability, frequency of crashes, and the rate of traffic flow. The primary goal of CACC is to maximize traffic flow subject to a maximum allowed speed. This requires maintaining smaller inter-vehicle distances which can be problematic as a platoon can become unstable as the target headway between cars is reduced. The main contribution of this dissertation is the development and evaluation of two heuristic approaches for dynamically adapting headway both of which attempt to minimize the headway while ensure stability. We present the design and analysis of a centralized and a distributed implementation of the algorithm. Our results suggest that dynamically adapting the headway time can improve the overall platoon traffic flow without the platoon becoming unstable

Safety and Operational Impact of Truck Platooning on Geometric Design Parameters

The most well-known benefits of heavy commercial vehicle (HCV) platooning are fuel savings and emission reductions. HCV platooning under SAE automation level 4 or 5 would also address the truck driver shortage by eliminating the driver from one or more HCVs in a platoon. This dissertation investigates the safety and operational implications of SAE level 4 HCV platooning on North American roadways. The research develops modified analytical models and micro-simulation models (PTV VISSIM) for analyzing impacts on two-lane rural highways, urban arterial roadways, and freeways. The study considers different time headways (0.6 sec and 1.2 sec) between the platooning vehicles, and three market penetration rates (0%, 5%, and 10%). The two-lane rural highways chapter investigates the passing sight distance (PSD) required to overtake an HCV platoon. The urban arterial roadways chapter compares existing traffic controls with traffic signal priority (TSP) for HCV platoons. The freeways chapter investigates freeway acceleration lane length on merging segments for HCV platooning operations. The findings suggest that two-HCV platooning with 0.6 sec time headway and a 5% market penetration rate can be allowed on designated North American roadways. With proper passing lanes, two-HCV platoons can be operated on two-lane rural highways that already permit long combination vehicle operations. Even with TSP, HCV platooning on urban arterial roadways at penetration rates higher than 5% at our selected intersection may, however, cause significant delays and overwhelm the traffic system. On freeways, two-HCV platooning at a 5% market penetration rate where the freeway acceleration lane is at least 600m long appear to be feasible. The study will assist transportation professionals and policymakers in understanding the consequences of HCV platoons and deciding whether to allow HCV platooning on North American roadways

Vehicle platoon modelling on arterial street

Upravljanje saobraćajem na gradskim arterijama zasniva se na usaglašavanju rada svetlosnih signala na unapred definisanom nizu raskrsnica. Osnovni cilj procesa upravljanja je da plotun vozila formiran na početnoj raskrsnici prođe celokupnu arteriju bez zaustavljanja. Za projektovanje sistema upravljanja na gradskim arterijama neophodno je poznavanje karakteristika kretanja plotuna vozila kako bi se uspostavila funkcionalna veza između parametara rada signala i objekta upravljanja. Uzimajući u obzir nedostatak jedinstvene i precizne definicije plotuna vozila koji predstavlja osnovni objekat upravljanja, u doktorskoj disertaciji je formiran model za definisanje plotuna vozila, koji pripadnost vozila plotunu utvrđuje na osnovu dva parametra, intervala sleđenja i pozicije vozila. Tokom kretanja duž arterije na svako pojedinačno vozilo u plotunu utiču spoljašnji i unutrašnji faktori. Pod uticajem navedenih faktora dolazi do modifikacije plotuna koja se manifestuje kroz fenomen skupljanja ili rasturanja plotuna. Osnovni nedostatak postojećih modela kretanja plotuna odnose se na činjenicu da opisuju isključivo fenomen rasturanja plotuna. Međutim, transformacija urbanog saobraćajnog sistema dovela je do promena u karakteristikama kretanja plotuna vozila, koje za posledicu imaju sve češću pojavu skupljanja plotuna, što je dokazano na osnovu rezultata istraživanja. U više od 52% registrovanih plotuna zabeležen je fenomen skupljanja, čime je dokazano da postojeći modeli (Robertson i HCM) odstupaju od realnih podataka. Istraživanjem je utvrđeno da su najznačajniji unutrašnji faktori koji dovode do modifikacije plotuna, veličina plotuna i brzina kretanja plotuna. U disertaciji je dokazano da veličina plotuna dominantno utiče na karakteristike kretanja plotuna. Na osnovu rezultata istraživanja formiran je model baziran na funkcionalnoj zavisnosti između veličine plotuna i karakteristika kretanja plotuna. Predloženi model, koji predstavlja osnovni cilj disertacije, opisuje oba fenomena i rasturanje i skupljanje plotuna, čime je eliminisan osnovni nedostatak postojećih modela. Primenom modela na deonicama gradskih arterija, dokazano je da je formirani model validan i jednostavan za primenu.Urban arterial street traffic management is based on the defined number of consecutive traffic signals coordination. The main objective of coordination is to ensure that platoon of vehicles, formed at the initial intersection, pass arterial street without stopping. In order to determine a functional relationship between the traffic signal parameters and the control object, i.e. platoon of vehicles, it is necessary to know the platoon movement characteristics. This dissertation proposes the model for platoon definition, considering the lack of a unique and precise platoon definition in the literature. Proposed model for platoon definition is based on two parameters, the time headway and the vehicle position. Platoon movement characteristics depend on external and on internal factors which affect each vehicle in the platoon. The influence of these factors results in the platoon modification, which can be manifested by the dispersion or compression phenomenon. Existing models of platoon movement characteristics can predict only platoon dispersion phenomenon, which is at the same time their main disadvantage. However, the urban transport system transformation has caused changes in the platoon movement characteristics, which, as a result, more often lead to platoon compression phenomenon. Based on the conducted research, the compression phenomenon is recorded in more than 52% of platoons. For this reason, relevant models such as Robertson and HCM model do not provide an accurate prediction of vehicle platoon movement characteristics. This research proves that platoon movement characteristics mostly depends on platoon size and platoon speed, but platoon size has a dominant effect. Proposed model of platoon movement characteristics, as a primary goal of this dissertation, can predict both, platoon dispersion and platoon compression, and overcome the main disadvantages of relevant models. By applying the proposed model at several arterial streets in Belgrade, it is proved that the model is valid and easy to use