Kentaro Wada

University of Tsukuba · College of Policy and Planning Sciences

Sags and tunnels are major bottlenecks, where the road capacity is reduced, and the “capacity drop” phenomenon occurs; however, there is no simple model or theory that can explain the formation and other characteristics of capacity drop. This paper presents a car-following model, which is equivalent to a continuum model in the Lagrangian coordinate...

The aim of this study is to analyze the stability of dynamic user equilibrium (DUE) with fixed departure times in unidirectional networks. Specifically, stochastic stability, which is the concept of stability in evolutionary dynamics subjected to stochastic effects, is herein considered. To achieve this, a new approach is developed by synthesizing...

In this study, we analyse the global stability of the equilibrium in a departure time choice problem using a game-theoretic approach that deals with atomic users. We first formulate the departure time choice problem as a strategic game in which atomic users select departure times to minimise their trip cost; we call this game the ‘departure time ch...

This paper presents a systematic approach for analyzing the departure-time choice equilibrium (DTCE) problem of a single bottleneck with heterogeneous commuters. The approach is based on the fact that the DTCE is equivalently represented as a linear programming problem with a special structure, which can be analytically solved by exploiting the the...

In this study, we analyse the convergence and stability of dynamic system optimal (DSO) traffic assignment with fixed departure times. We first formulate the DSO traffic assignment problem as a strategic game wherein atomic users select routes that minimise their marginal social costs, called a ‘DSO game’. By utilising the fact that the DSO game is...

In this study, we analyse the global stability of the equilibrium in a departure time choice problem using a game-theoretic approach that deals with atomic users. We first formulate the departure time choice problem as a strategic game in which atomic users select departure times to minimise their trip cost; we call this game the 'departure time ch...

In this study, we construct a simplified model of the speed control of an automated vehicle (AV) to avoid stopping a platoon of following vehicles in a coordinated signal-controlled corridor in which manual and automated vehicles are mixed. We then analyze how signal delays, number of stops, and CO2 emissions vary depending on the AV penetration ra...

This paper investigates the impact of work from home (WFH) on the temporal agglomeration (dis-) economies associated with the morning commute in cities. Specifically, we extend the equilibrium model by Takayama¹⁾ to a model including the effects of WFH, and analyze its equilibrium and social optimum both theoretically and numerically. We then show...

This study develops a queueing model based on a continuum traffic flow model that endogenously describes the capacity drop (CD) phenomenon at freeway sag and tunnel bottlenecks and analyzes the characteristics of the traffic breakdown probability. The model describes the traffic breakdown probability in two steps, distinguishing between fluctuation...

This study analyzes two car-following models based on the Intelligent Driver Model+ (IDM+) for developing an endogenous and easy-to-use microsimulation model that can represent the capacity drop (CD) phenomenon in freeway sag sections. One is a model in which the safety time gap varies depending on the location, suggested by the recent CD theory, a...

Traffic congestion is closely associated with various social issues that must be solved urgently. With the recent advancement of machine learning technologies, diverse methods for predicting traffic congestion have been developed. Specifically, traffic prediction using deep learning can provide highly accurate performance. Nevertheless, several dif...

This paper proposes a macroscopic model to describe the equilibrium distribution of passenger arrivals for the morning commute problem in a congested urban rail transit system. We use a macroscopic train operation sub-model developed by Seo, Wada, and Fukuda (2017, 2022) to express the interaction between the dynamics of passengers and trains in a...

This paper explores the improvement mechanisms of traffic performance such as the traffic capacity before congestion and the queue discharge flow rate by the audible speed recovery information provision introduced as a congestion measure at the Kobotoke tunnel of Chuo Expressway, Japan. Specifically, we apply the recent advanced traffic flow theory...

Published in JSTE Journal of Traffic Engineering (in Japanese).

A novel train operation scheme that includes express/local services in a single train using fast coupling technology is proposed herein. Specifically, as a typical train operation based on the aforementioned concept, we propose a scheme that generates a new local train from an express train at every express station in the outbound direction and, co...

Traffic congestion brings about various social issues to be solved urgently. With the recent advancement of machine learning technologies, various methods for predicting traffic congestion have been developed. Specifically, traffic prediction using deep learning can pro- vide highly accurate performances. However, there are several problems due to...

This study investigates dynamic system-optimal (DSO) and dynamic user equilibrium (DUE) traffic assignment of departure/arrival-time choices in a corridor network. A morning commute problem with a many-to-one pattern of origin–destination (OD) demand and an evening commute problem with a one-to-many OD pattern are considered. Specifically, we first...

This paper examines the theoretical properties of a departure time choice equilibrium in a tandem bottleneck network with endogenous demand distributions that are determined through an upper-level choice (e.g., mode choice and location choice). We first show that, for two-bottleneck networks, we can analytically classify equilibrium flow patterns b...

This paper proposes a novel train operation scheme for high-frequency railway systems with the fast train coupling technology that makes a possible to change the number of vehicles for each train flexibly. Specifically, the proposed scheme generates a new local train from an express train at every stop station in the outbound direction, and convers...

Urban rail transit often operates with high service frequencies to serve heavy passenger demand during rush hours. Such operations can be delayed by two types of congestion: train congestion and passenger congestion, both of which interact with each other. This delay is problematic for many transit systems, since it can be amplified due to the inte...

Published in JSTE Journal of Traffic Engineering (in Japanese). The “capacity drop (CD)” phenomenon, which means the queue discharge flow rate is less than the traffic capacity before congestion, is observed at freeway bottlenecks in general. Although this phenomenon has been known for a long time, its precise mechanism is not necessarily clear. T...

Published in JSTE Journal of Traffic Engineering (in Japanese). This study investigates driving behaviors for mitigating the capacity drop (CD) phenomenon, which means the queuing discharge flow rate is less than the traffic capacity before congestion, at freeway sag and tunnel bottlenecks. Specifically, exploiting a recent advanced continuum traff...

A bottleneck is a road segment whose traffic capacity is lower than that of its vicinity. Since traffic congestion occurs when an arrival traffic flow rate to the bottleneck exceeds its capacity, understanding, and description of bottleneck behaviors are essential for establishing congestion mitigation strategies. This article contains discussions...

Flow breakdown is defined as a transition from a free-flow state to a congested state of a traffic state at a certain location. It occurs when the arrival flow to the location exceeds its capacity. This article contains discussions on characteristics of flow breakdown, such as main causes, stochastic nature, and long-term variations. We also discus...

This paper reviews the recent advances in the theory of dynamic traffic equilibrium assignment problems. We mainly discuss a Lagrange coordinate system approach enabling us to analyze the complex network traffic flows transparently. Two types of description of traffic within the approach—traditional fluid approximation models and emergent atomic/pa...

This paper proposes a macroscopic model to describe the equilibrium distribution of passenger arrivals for the morning commute problem in a congested urban rail transit system. We employ a macroscopic train operation sub-model developed by Seo et al. (2017a,b) to express the interaction between dynamics of passengers and trains in a simplified mann...

Due to the development of information technology, several studies have been conducted on short-term traffic forecasting in intelligent transportation systems during the last few decades. Specifically, predicting traffic congestion plays a crucial role in smoothing traffic flow, so that several models for predicting it have been proposed. This study...

This study investigates dynamic system-optimal (DSO) and dynamic user equilibrium (DUE) traffic assignment of departure/arrival-time choices in a corridor network. The morning commute problems with a many-to-one pattern of origin-destination demand and the evening commute problems with a one-to-many pattern are considered. In this study, a novel ap...

This paper presents a systematic approach for analyzing the departure-time choice equilibrium (DTCE) problem of a single bottleneck with heterogeneous commuters. The approach is based on the fact that the DTCE is equivalently represented as a linear programming problem with a special structure, which can be analytically solved by exploiting the the...

Chapter for International Encyclopedia of Transportation, Vickerman, R. (Ed.), Elsevier Science. A bottleneck is a road segment whose traffic capacity is lower than that of its vicinity. Since traffic congestion occurs when an arrival traffic flow rate to the bottleneck exceeds its capacity, understanding and description of bottleneck behaviors are...

Chapter for International Encyclopedia of Transportation, Vickerman, R. (Ed.), Elsevier Science. Flow breakdown is defined as a transition from a free-flow state to a congested state of a traffic state at a certain location. It occurs when the arrival flow to the location exceeds its capacity. This article contains discussions on characteristics of...

In this study, we analyse the convergence and stability of dynamic system optimal (DSO) traffic assignment with fixed departure times. We first formulate the DSO traffic assignment problem as a strategic game wherein atomic users select routes that minimise their marginal social costs, called a 'DSO game'. By utilising the fact that the DSO game is...

This study conducts an empirical analysis of the capacity drop phenomenon at sag bottlenecks based on the recent advanced continuum traffic flow theory. We first show the underlying phenomena, components, and consequences of the theory in a concise manner. We then compare several theoretical predictions with real data, qualitatively and quantitativ...

The aim of this study is to analyze the stability of dynamic user equilibrium (DUE) with fixed departure times in unidirectional networks. Specifically, stochastic stability, which is the concept of stability in evolutionary dynamics subjected to stochastic effects, is herein considered. To achieve this, a new approach is developed by synthesizing...

Seo et al. (2017) proposed a fundamental diagram (FD) of urban rail transit to describe the interaction between passenger demand and train operation, in a simple manner. This paper investigates their proposed FD and its variants by using empirical data from the Boston subway system. Specifically, three FD models, which are based on different assump...

Sags and tunnels are major bottlenecks, where the road capacity is reduced, and the “capacity drop” phenomenon occurs; however, there is no simple model or theory that can explain the formation and other characteristics of capacity drop. This paper presents a second-order car-following model, which is equivalent to a continuum model in the Lagrangi...

The aim of this study is to analyze the stability of the dynamic user equilibrium (DUE) with fixed departure times in unidirectional networks. Specifically, the stochastic stability of the equilibrium, which is the concept of stability in a day-to-day dynamics subjected to stochastic effects, is herein considered. To achieve this, a new approach is...

50 days' free access (~Sep. 6th, 2019): https://authors.elsevier.com/a/1ZPqQhVEAp4Ir

This paper has been accepted for a poster presentation to the 23rd International Symposium on Transportation and Traffic Theory (ISTTT) and for the ISTTT special issue in Transportation Research Part C. Please find the published version (Open Access) from the following URL: https://doi.org/10.1016/j.trc.2019.05.012

Daganzo (1997) proposed a kinematic wave model of a traffic system with priority vehicles and special lanes, where the priority vehicles can use both regular and special lanes, but the regular vehicles can only use the regular lanes. Further in Daganzo et al. (1997), the Incremental Transfer (IT) principle was applied to devise a Cell Transmission...

[MPRA Paper No. 90361] This paper presents a systematic approach for analyzing the departure-time choice equilibrium (DTCE) problem of a single bottleneck with heterogeneous commuters. The approach is based on the fact that the DTCE is equivalently represented as a linear programming problem with a special structure, which can be analytically solve...

This study considers an optimal coordinated traffic signal control under both deterministic and stochastic demands. We first present a new mixed integer linear programming (MILP) for the deterministic signal optimization wherein traffic flow is modeled based on the variational theory and the constraints on a signal control pattern are linearly form...

This paper extends the theory of tradable bottleneck permits system to cases with multiple period markets and designs its implementation mechanism. The multiple period markets can achieve more efficient resource allocation than a single period market when users’ valuations of tradable permits change over time. To implement the multiple period tradi...

This paper summarizes recent advances in the kinematic wave (KW) theory of traffic flows. First, we review the variational formulation of kinematic waves and its application together with pointing out the limitations of its conventional analysis methods. Second, the KW theories for the network traffic are introduced. Specifically, we review and sum...

Urban rail transit often operates with high service frequencies to serve heavy passenger demand during rush hours. Such operations can be delayed by train congestion, passenger congestion, and the interaction of the two. Delays are problematic for many transit systems, as they become amplified by this interactive feedback. However, there are no tra...

This study considers an optimal coordinated traffic signal control under both deterministic and stochastic demands. We first present a new mixed integer linear programming (MILP) for the deterministic signal optimization wherein traffic flow is modeled based on the variational theory and the constraints on a signal control pattern are linearly form...

The link transmission model (LTM), which combines the Newell’s simplified kinematic wave theory (Newell,1993) and the demand-supply framework (Daganzo,1994; Lebacque,1996), has been recognized as an efficient and accurate way for simulating traffic flow in large-scale networks. The LTM was proposed by Yperman et al. (2005) in discrete time form ini...

The inter-driver variability of follow-the-leader behavior is well recognized as a main cause of bottleneck phenomenon on expressway basic segment. The bottleneck phenomenon observed at sag sections on Japanese expressways is an example where the accumulation of driving behavior variability results in obvious capacity drop and probabilistically occ...

This paper clarifies the relationship between a Macroscopic Fundamental Diagram (MFD) and congestion patterns on a general network with one-to-many OD pairs. Specifically, we formulate a new inverse problem of the dynamic user equilibrium assignment problem for a given congestion pattern. The proposed problem is formulated as a system of linear equ...

This paper proposes an approximation method of expected delay for signalized arterial roads under stochastic arrivals. This method is based on variational theory of traffic flow (VT). In VT under stochastic arrivals, traffic flow dynamics is described as the solution of the stochastic shortest path problem in the network on a space-time domain, whi...

This paper corrects and modifies some properties of the Iryo's (2011) solution algorithm of Nash equilibrium in dynamic traffic assignment, in which each discretized vehicle is assigned on its shortest path one-by-one in an appropriate order. Specifically, we first give a counterexample to the theorem that guarantees the algorithm produces a Nash e...

Akamatsu et al. (2006) proposed a new transportation demand management scheme called “tradable bottleneck permits” (TBP), and proved its efficiency properties for a single bottleneck model. This paper explores the properties of a TBP system for general networks. An equilibrium model is first constructed to describe the states under the TBP system w...

Urban mass transit often operates with high service frequencies to serve large passenger demand, such as those during morning commute. Their objective is to transport as many passengers as quickly as possible. To do so, they require careful planning because their operation can be delayed by two types of congestion, namely, train-congestion (i.e., k...

Urban mass transit such as metro plays a significant role in transportation in metropolitan areas. Its most notable usage is the morning commute situation. It is known that such transit can be delayed due to congestion under excessive passenger demand. However, there are no tractable models of transit systems considering physics of its delay and co...

This paper proposes the analytical assessment we propose a method for analytically assessing impacts on traffic state. The impacts are assessed on the basis of stochastics of sensing data and driving behavior at a highway section with signalized intersections; the proposed analytical assessment method is based on variational theory. The fluctuation...

The purpose of this paper is to empirically explore the features of Macroscopic Fundamental Diagram (MFD) linking vehicle accumulation and traffic production for Sendai and Kyoto arterial road networks in Japan. By investigating MFDs based on detectors data of 5-minute periods throughout one year (5/1/2012 ~ 4/30/2013), the following features were...

Understanding free-flow speed and its variance is important to evaluate the safety and performance of expressways. Not only the geometric factors considering directly in geometric element design criteria, but also other factors which are not explicitly considered (for ex., number of lanes, width of lanes, center median etc.) affect the variation of...

This paper proposes a solution method of the coordinated traffic signal control problem with physical queues (Wada et al., 2015) by using cross-entropy (CE) method. The underlying problem was recently developed and is formulated as a concise optimization problem that has network structures. By combining these special structures with the CE-method,...

This paper proposes a novel formulation for optimizing a system of signalized intersections. The proposed formulation employs the following two approaches: (i) the spatial and temporal traffic flow dynamics is described by the variational theory of kinematic waves; (ii) a traffic signal control is modeled as an “on-off pattern” that satisfies physi...

This paper shows the relationship between a Macroscopic Fundamental Diagram (MFD) and congestion patterns in a general network. Specifically, for a given congestion pattern, we derive a network throughput analytically by solving a dynamic user equilibrium (DUE) problem under a steady state condition. By using this analytical formula, we can investi...

A sag section is a road segment on an expressway in which the vertical slope increases at a small but constant rate. Sag sections are the main traffic bottlenecks on Japanese expressways. Variations in individual car-following behavior are generally recognized as the key cause of traffic breakdown. This research was conducted to develop a quantitat...

This paper presents a transparent approach to the analysis of dynamic user equilibrium and clarifies the properties of a departure- time choice equilibrium of a corridor problem where discrete multiple bottlenecks exist along a freeway. The basis of our approach is the transformation of the formulation of equilibrium conditions in a conventional “E...

Probe data provide rich information of vehicle trajectories which include driving modes (e.g., acceleration/deceleration) and reflect traffic conditions. However, most of the applications only use probe data to measure travel times. This paper presents two alternative applications of vehicle trajectories on signalized arterials: one is a traffic si...

The purpose of this paper is to explore the features of the Macroscopic Fundamental Diagram (MFD) for Sendai road networks. In order to achieve this, we used the observed data of 5-minute periods throughout one year (5/1/2012-4/30/2013) to draw the MFDs for Sendai road networks. The result of the empirical verification shows the following: (1) the...

Akamatsu, 2007a and Akamatsu, 2007b proposed a new dynamic traffic congestion control scheme called tradable network permits, and demonstrated its efficiency properties for general road networks. To implement tradable permit markets, this paper proposes a novel auction mechanism with capacity control. This mechanism employs an evolutionary approach...

Akamatsu, Sato, and Nguyen (2006) and Akamatsu (2007a,b) proposed a new dynamic traffic congestion control scheme—the tradable network permit—and proved its efficiency properties for general road networks. To implement tradable permit markets successfully, this paper proposes a novel auction mechanism with capacity control. Assuming that each user...

This study quantitatively analyzes flow of emergency goods supplied by national and prefectural governments at the Great East Japan Earthquake on the 11th of March, 2011. Historically, flow of emergency goods has not been well retained because the flow is ephemeral. Therefore, just after the earthquake, shipping records mostly handwritten were coll...

This paper proposes a railway operation control strategy that prevents delay propagation in high-frequency railway systems. We first formulate a dynamical system of a train motion that includes two types of delay propagation models: one is a passenger boarding model at each station, and the other is a train-following model in each railway section b...

This paper proposes a new distributed signal control policy based on a trad- able network permits system, which was proposed in Akamatsu et al. [2006] and Akamatsu [2007a,b], taking into account a semi-dynamic traffic flow. This signal control policy can achieve a global optimal traffic flow pattern by exploiting only local information. Specificall...

This paper proposes a new auction mechanism for implementing the tradable network permit markets. Assuming that each user makes a trip from an origin to a destination along a path in a specific time period, we design an auction mechanism that enables each user to purchase a bundle of permits corresponding to a set of links in the user's preferred p...

Akamatsu et al. (2006, 2007a, b) proposed a new dynamic traffic congestion control scheme called “tradable bottleneck permits” (TBP). To mitigate both queuing congestion and flow congestion, Wada and Akamatsu (2010a, b) developed a hybrid scheme combining TBP and congestion pricing, and proved its efficiency properties in a deterministic situation....

This paper proposes a new transportation demand management (TDM) scheme that simultaneously mitigates both queuing and flow congestion, and does not require detailed user information. This scheme is built upon the theory of “tradable bottleneck permits”(TBP), which was proposed in Akamatsu et al.(2006). We first construct a micro mechanism of the p...

Previously, Akamatsu et al. (2006) proposed “tradable bottleneck permits” as a new transportation demand management scheme and proved the efficiency thereof for a general network. To implement such a scheme, we propose a multi-agent system for general transportation networks. The aim of this system is to achieve a socially optimal state in which th...