Toru Seo

• Doctor of Engineering
• Associate Professor at Tokyo Institute of Technology

Probe vehicles provide some of the most useful data for road traffic monitoring because they can acquire wide-ranging and spatiotemporally detailed information at a relatively low cost compared with traditional fixed-point observation. However, current GPS-equipped probe vehicles cannot directly provide us volume-related variables such as flow and...

Traffic state estimation (TSE) refers to the process of the inference of traffic state variables (i.e., flow, density, speed and other equivalent variables) on road segments using partially observed traffic data. It is a key component of traffic control and operations, because traffic variables are measured not everywhere due to technological and f...

The fundamental diagram (FD), also known as the flow-density relation, is one of the most fundamental concepts in the traffic flow theory. Conventionally, FDs are estimated by using data collected by detectors. However, detectors' installation sites are generally limited due to their high cost, making practical implementation of traffic flow theore...

This study proposes a unified optimization framework for strategic planning of shared autonomous vehicle (SAV) systems that explicitly and endogenously considers their operational aspects based on macroscopic dynamic traffic assignment. Specifically, the proposed model optimizes fleet size, road network design, and parking space allocation of an SA...

In a congested urban road network, it is important to reduce passenger travel time and delay by implementing appropriate traffic signal controls. Previous studies have mainly focused on vehicle travel times or queue lengths around signals. However, as ridesharing has become popular in recent years, a new line of research delves into prioritizing ri...

Vehicle trajectories can offer the most precise and detailed depiction of traffic flow and serve as a critical component in traffic management and control applications. Various technologies have been applied to reconstruct vehicle trajectories from sparse fixed and mobile detection data. However, existing methods predominantly concentrate on single...

This note describes a technical overview of UXsim, an open source macro/mesoscopic traffic simulator in pure Python programming language. UXsim is based on Kinematic Wave model (more specifically, mesoscopic version of Newell's simplified car-following model) and dynamic user optimum-like route choice principle, which are well established methodolo...

Vehicle trajectories can offer the most precise and detailed depiction of traffic flow and serve as a critical component in traffic management and control applications. Various technologies have been applied to reconstruct vehicle trajectories from sparse fixed and mobile detection data. However, existing methods predominantly concentrate on single...

The shared autonomous vehicle (SAV) system is considered as an efficient transportation mode in the future. In the literature, optimization of SAV systems has been extensively studied. However, SAV systems could bring greater social benefits if we could use them with existing public transportation systems, such as bus rapid transit (BRT), in an int...

Traffic congestion is a serious problem in urban areas. Dynamic congestion pricing is one of the useful schemes to eliminate traffic congestion in strategic scale. However, in the reality, an optimal dynamic congestion pricing is very difficult or impossible to determine theoretically, because road networks are usually large and complicated, and be...

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...

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...

As one of the measures to alleviate traffic congestion, the usefulness of dynamic congestion toll is proposed to consider the fluctuation of traffic demand within a day. In addition, a trial-and-error congestion toll method is proposed to deal with the asymmetric information between a toll entity and road users. In this research, we construct a tri...

A reinforcement learning-based dynamic congestion pricing method for morning commute problems is proposed. In this method, tolls are iteratively updated day by day based on observable information such as traffic volume. The advantage of the method is two fold. First, the method does not require travelers personal preferences such as value of time....

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...

This study proposes a unified optimization problem for aggregated versions of vehicle routing problem with pickup and delivery with time windows, dynamic ridesharing matching, fleet size optimization, road network design, and parking space allocation of shared autonomous vehicle (SAV) systems based on dynamic traffic assignment. The proposed proble...

A trial-and-error congestion pricing scheme finds the optimal toll based only on observable information (e.g., travel time) without information on travelers’ personal preferences that are often unobservable in practice (e.g., value of time, scheduling preference). This paper proposes a trial-and-error pricing scheme for the morning commute problem,...

The trial-and-error approach for congestion pricing finds the optimal toll based only on observable information (e.g., travel time, traffic state) without information on travelers' personal preferences that are often unobservable in practice (e.g., value of time, demand function). This feature makes the method practically useful by solving the well...

In an era of highly developed information and communication technologies, social networks play an important role in all aspects of businesses, including transportation. The use of dynamic ridesharing systems, which are systems in which travelers can find partner(s) to share their upcoming rides in real time, is also expected to be affected by the i...

A dynamic ridesharing system (DRS) is a system where users can find ridesharing partner(s) at any time, even shortly before making a trip. A DRS that does not consider individual preferences may cause dissatisfied matchings of users in a shared vehicle and lead to abandonment of DRS in the long term. To investigate the evolution of DRS, such as lon...

Small imaging satellites (SISs), which has attracted attention in remote sensing field recently, would provide a novel type of data for traffic state estimation (TSE): that is, spatial distribution of every cars in anywhere on our planet with relatively short time interval. This nature is particularly useful to complement connected vehicle (CV) dat...

The fundamental diagram (FD), also known as the flow--density relation, is one of the most fundamental concepts in the traffic flow theory. It describes the relation between equilibrated flow, density, and speed in traffic flow. Conventionally, FDs are estimated by using fixed roadside sensors such as detectors. On the other hand, there is a paucit...

Smart ridesharing system (SRS) is a ridesharing system integrated with information and communication technology. We formulate a passenger matching problem by considering user preference in SRS. This study aims to investigate day-to-day dynamics and characteristics of passenger matching problem in SRS. A modified stable roommates problem is adopted...

A fundamental diagram (FD), also known as flow–density relation, is one of the most important principles in traffic flow theory. It would be valuable if an FD could be calibrated by using GPS-equipped probe vehicles; since they can continuously collect data from wide spatiotemporal area, compared to traditional fixed sensors. This paper proposes me...

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...

This article proposes a framework for an interactive activity-travel survey method, implementable on mobile devices such as smartphones. The proposed method was developed to reduce the burden (i.e., frequency of questions) on respondents in long-term behavioral surveys, without relying on external data sources. The method employs an online travel c...

“Sharing economy”, including car-sharing and ride-sharing, and autonomous driving will change our society and transport in the near future. To effectively introduce ride-share-based transport service into a society, we need to estimate the required number of vehicles and determine route and schedule of vehicles, based on travelers' activity. We als...

Probe person survey has received great deal of attentions, as it can automatically collect traveler's spatiotemporal traces using sensors like GPS, making a long-term travel survey easier. However, it is still difficult to collect all of the survey results automatically, because trip purpose—one of the most important characteristics of travel—is no...

Most studies on travel time reliability (TTR) for roads are single-route section basis due to the availability of sufficient number of travel time observations. Recent years, there have been increasing possibilities of observing network-wide traffic states for long time period with the rapid accumulations of rich probe datasets and it is expected t...

雑誌『交通工学』第52巻4号の特集「マクロ交通流理論の最前線と実務への応用」 (交通工学研究会, 2017) に関連する練習問題です．VTをExcel上に実装したものです．詳細は https://www.researchgate.net/publication/320087319 をお読みください． Excel implementation of VT to demonstrate contents of a special issue in Japanese journal ”Traffic Engineering”.

雑誌『交通工学』第52巻4号の特集「マクロ交通流理論の最前線と実務への応用」 (交通工学研究会, 2017) に関連する練習問題です．追従モデルのXモデルをExcel上に実装したものです．詳細は https://www.researchgate.net/publication/320087319 をお読みください． Excel implementation of X-model to demonstrate contents of a special issue in Japanese journal ”Traffic Engineering”.

雑誌『交通工学』第52巻4号の特集「マクロ交通流理論の最前線と実務への応用」 (交通工学研究会, 2017) に関連する練習問題です．CTMをExcel上に実装したものです．詳細は https://www.researchgate.net/publication/320087319 をお読みください． Excel implementation of CTM to demonstrate contents of a special issue in Japanese journal ”Traffic Engineering”.

雑誌『交通工学』第52巻4号の特集「マクロ交通流理論の最前線と実務への応用」 (交通工学研究会, 2017) に関連する練習問題です．交通流のセルオートマトンCA(L)をExcel上に実装したものです．詳細はhttps://www.researchgate.net/publication/320087319 をお読みください． Excel implementation of CA(L) to demonstrate contents of a special issue in Japanese journal ”Traffic Engineering”.

Automated and connected vehicles (ACVs) have received a great deal of attention. Indeed, their full market penetration will be desirable in terms of traffic efficiency, as ACVs can efficiently drive by precisely and instantaneously communicating, recognizing, and reacting to other ACVs. However, it is not yet certain whether traffic efficiency is i...

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...

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...

"Sharing economy", including car-sharing and ride-sharing, will change our society and transport in the near future. To effectively introduce ride-sharing service into our society, we need to determine route and schedule of vehicles based on users’ activity. We also need to understand how users’ activity patterns affect the performance of this shar...

Automated and connected vehicles (ACVs) have received a great deal of attention. Indeed, their full market penetration will be desirable in terms of traffic efficiency, as ACVs can efficiently drive by precisely and instantaneously communicating, recognizing, and reacting to other ACVs. However, it is not yet certain whether traffic efficiency is i...

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...

A fundamental diagram (FD), also known as flow–density relation, is one of the most important principles in traffic flow theory. It would be valuable if an FD could be calibrated by GPS-equipped probe vehicles; since they can continuously collect data from wide spatiotemporal area, compared to traditional fixed sensors. This paper proposes methods...

This paper proposes a method of estimating the traffic state based on new probe vehicle data that contain the spacing and position of probe vehicles. In this study, the probe vehicles were assumed to observe spacing by utilizing an advanced driver assistance system, which has been implemented in practice and is expected to spread in the near future...

Ridesharing system has been recognized as an efficient transport mode to solve the environment, energy, traffic congestion issues. In recent researches, user preference was revealed as an important factor to enhance the performance and reliability of ridesharing systems. With the development in ICT, internet-enabled devices and social network enabl...

This paper proposes a method for estimating traffic state from data collected by the advanced probe vehicles, namely, probe vehicles with spacing measurement equipment. The probe vehicle data are assumed to include spacing information, in addition to conventional position information. The spacing information is collected as secondary products from...

This paper proposes a method of estimating a traffic state based on probe vehicle data that contain spacing and position of probe vehicles. The probe vehicles were assumed to observe spacing by utilizing an advanced driver assistance system, that has been implemented in practice and is expected to spread in the near future. The proposed method reli...

We propose an econometric-based model for the behavior of pedestrian walking that implicitly considers strategic or tactical decisions. In real situations, it is only possible to observe pedestrian trajectories and final choices of destination (e.g., the ticket gate they have actually chosen) and the targeted destination en route is latent and unob...

Analysing pedestrian behaviour is important for better design of facility, evacuation planning and so on. In this study, we propose an econometric based pedestrians' walking behaviour model. In real situations, it is only possible to observe pedestrians' trajectories and their final choice results on destination (e.g. the ticket gate they actually...