Showing papers in "Transportmetrica B-Transport Dynamics in 2017"

Agent-based day-to-day adjustment process to evaluate dynamic flexible transport service policies

Abstract: Advances in information and communications technologies, connected vehicle technologies, and Big Data have made it viable for public agencies to offer efficient flexible transit services for travel demand that is predominantly dynamic to the system. There is a clear gap in methodologies to evaluate the user equilibrium for flexible transport services (FTS). In this study we lay the groundwork for studying the equilibrium of these systems and propose an agent-based adjustment process to evaluate the properties of a stable state as an agent-based stochastic user equilibrium. To validate the proposed process and illustrate its effectiveness in measuring the effect of changes in FTS operating parameters on ridership three sets of experiments are conducted: (1) illustration with a simple 2-link network, (2) evaluation of a dynamic dial-a-ride problem, and (3) illustration using real data from Oakville, Ontario consisting of 57 zones and 2000 commuters.

Most reliable path-finding algorithm for maximizing on-time arrival probability

Abstract: Finding the most reliable path that maximizes the probability of on-time arrival is commonly encountered by travelers facing travel time uncertainties. However, few exact solution algorithms have been proposed in the literature to efficiently determine the most reliable path in large-scale road networks. In this study, a two-stage solution algorithm is proposed to exactly solve the most reliable path problem. In the first stage, the upper and lower bounds of on-time arrival probability are estimated. Dominance conditions and the monotonic property of the most reliable path problem are then established. In the second stage, the multi-criteria label-setting approach is utilized to efficiently determine the most reliable path. To illustrate the applicability of the proposed solution algorithm, a comprehensive case study is carried out using a real road network with stochastic travel times. The results of case study show that the proposed solution algorithm has a remarkable computational advantage ove...

Multi anticipative bidirectional macroscopic traffic model considering cooperative driving strategy

Abstract: Recent development of information and communication technologies (ICT) has enabled vehicles to timely communicate with others through wireless technologies, which will form future (intelligent) traffic systems (ITS) consisting of so-called connected vehicles. Cooperative driving with the connected vehicles is regarded as a promising driving pattern to significantly improve transportation efficiency and traffic safety. In the vast literature of traffic flow theory, there are continuum models considering multiple forward anticipative strategy, where the driver reacts to many leaders. Few study effort has been undertaken to include bidirectional driving strategy, where the driver reacts to both direct leader and direct follower, in the continuum traffic flow models. This paper aims to derive a continuum traffic model considering both multiple forward and backward driving strategy. It is shown that the derived model is a generalised version of a current continuum model for ITS and can improve important properties of such bidirectional (continuum) model.

Capacity drop: a comparison between stop-and-go wave and standing queue at lane-drop bottleneck

Abstract: In freeways, the capacity drop means that the maximum traffic flow is higher than congestion discharge rates there. Various capacity drop magnitudes have been empirically observed before. But the mechanism behind this wide capacity drop range is not yet found. This contribution fills in the gap by relating the congestion discharge rates to different congestions in empirical observations. Two days’ data show that the outflows of stop-and-go waves are always lower than those of standing queues. Different discharge rates, ranging from 5220 to 6040 veh/h at the same site, always accompany different congestion states. Moreover, the different observations show that a higher discharge rate means a higher density in the free-flow branch in the fundamental diagram. This contribution shows that discharging rates probably could be controlled by transforming the congestion states. For instance, transforming a stop-and-go wave into a standing queue at a bottleneck might increase the bottleneck throughput.

Automatic fitting procedure for the fundamental diagram

Abstract: The fundamental diagram of a road, including free-flow capacity and queue discharge rate, is very important for traffic engineering purposes. In the real word, most traffic measurements come from stationary loop detectors. This paper proposes a method to fit Wu's fundamental diagram to loop detector data. Wu's fundamental diagram is characterised by five parameters, being free-flow speed, wave speed, free-flow capacity, queue discharge rate and jam density. The proposed method entails fixing the wave speed and the free-flow speed. The method consists of two steps. We first use a triangular fundamental diagram to separate the congested branch from the free-flow branch. Then, the remaining three parameters of Wu's fundamental diagram are fitted on each branch using a least-square fit. This method is shown to be robust for cases tested in real life, and hence very noisy, data.

Modeling the activity profiles of a population

Abstract: Chains of activities performed during the course of the day are interconnected such that participation in one activity and the time allocated to that specific activity correspondingly influence the time-use behavior of a traveler along the course of the day. This points to the importance of analyzing trajectories of patterns as a set of activities with such specific characteristics as start time, duration, and sequence, rather than simply analyzing participation in each activity singularly. In this paper we present a methodology to answer a main question in the trajectory analysis: How to generate activity patterns trajectories, and how to conduct useful analysis that eventually makes inferences drawn from the time-use behavior of individuals applicable to the population-at-large possible? The methodology presented in this paper can be applied to synthetize chains of activities and their space–time distribution. It starts with clustering the activity patterns into a small set of representative pat...

A link partitioning approach for real-time control of queue spillbacks on congested arterials

Abstract: In oversaturated urban traffic conditions when traffic demand exceeds capacity at signalised intersections, queues fail to clear during the allocated green times. Once a queue reaches the upstream intersection in an arterial, a queue spillback occurs that reduces the upstream link capacity. To mitigate the negative impacts of spillbacks, this article introduces a real-time adaptive traffic signal control method for global management of spillbacks along signalised arterials. The key idea of the proposed method is to implement a real-time partitioning of the arterial to detect critical cluster(s) of consecutive links with oversaturated traffic conditions. The partitioning approach enables to develop locally smaller-sized decentralised signal control strategies operating on the most upstream and downstream intersections of each cluster. Micro-simulation investigations on a real-world arterial site demonstrate the benefits of the proposed approach compared to an existing pre-timed signal control strat...

Modelling travellers’ en-route path switching in a day-to-day dynamical system

Abstract: Travellers’ en-route path switching is a very common travel adjustment behaviour which can significantly influence the whole day-to-day network traffic flow evolution process. This study encapsulated travellers’ sequential path adjustment mechanism into a day-to-day dynamical system, to capture travellers’ en-route switching effect without actually building a complicated within-day model to go with. According to different path choice behaviours and traffic information sources, three traveller groups were contained in the dynamical system, including the conservative travellers, the adventurous travellers unequipped with advanced traveller information systems (ATISs) and the ATIS-assisted adventurous travellers. In the proposed day-to-day dynamical model, a fixed point problem was established for achieving the heterogeneous traffic flow caused by travellers’ en-route path switching. Some stability analysis of the proposed dynamical system was accomplished in the numerical experiment. The effect of e...

An evacuation route choice model based on multi-agent simulation in order to prepare Tsunami disasters

Abstract: Minimising the damage caused by natural disasters such as tsunamis in vulnerable coastal areas requires the development of an emergency action plan. An evacuation plan can reduce the damaging impac...

Analytical equilibrium of bicriterion choices with heterogeneous user preferences: application to the morning commute problem

Abstract: The morning commute problem, introduced in Vickrey [1969. “Congestion Theory and Transport Investment.” American Economic Review 56: 251–260], addresses the equilibrium trip schedule of the users for commuting through a single bottleneck with fixed capacity over the morning peak. In this paper, we adapt the concept of the efficient frontier from Portfolio Theory [Markowitz, H. 1952. “Portfolio Selection.” The Journal of Finance 7 (1): 77–91] to propose an analytical solution to the morning commute problem with a general distribution of the schedule preferences over time and a continuous joint distribution of schedule penalty preferences over the population of the commuters. On this basis, we analytically derive the equilibrium arrivals of the heterogeneous commuters to the bottleneck given the independent probability distributions of earliness and lateness penalty factors. We also propose a method to retrieve independent probability distributions of the schedule penalty factors in the equilibrium ...

An iterative learning approach for anticipatory traffic signal control on urban networks

Abstract: Traffic signal control on urban road networks offers high opportunity to improve traffic operations. Among others, anticipatory control determines signal timings to optimize network performance, taking into account explicitly the route choice responses and resulting (equilibrium) network flow patterns. However, the optimal control decisions are usually calculated using equilibrium flow models that are in general only a coarse representation of reality. As a result, model–reality mismatch often leads to suboptimal conditions characterized by unexpected congestion effects. This paper presents a novel method to support control decisions for practical applications in real traffic systems that operate repeatedly, for instance from week to week, month to month, and in the presence of flow measurements. The proposed method generates a sequence of control settings to track the real flow response, by observing errors between modeled flows and the measurements. Improvement in the control performance is achi...

Traffic flow sensitivity to parameters in viscoelastic modelling

Abstract: This paper presents viscoelastic modelling of traffic flows briefly first and then shows numerical simulation results of ring traffic flow sensitivity to model parameters, such as viscoelasticity, average vehicle length, braking distance, and characteristic length used to define relaxation time. It was found that traffic flow pattern formation is dramatically sensitive to viscoelasticity and fundamental diagram which is explicitly impacted by average vehicle length and braking distance, implying that drivers' self-organisation ability is significant in determining the intensity of traffic wave interaction. Since the decrease of characteristic length can lead to a relevant change of traffic relaxation time, the length can play a sensitive role in changing traffic wave structures. Optimisation of traffic regulations is necessary for the well operation of a segmental or ring road.

A predictive continuum dynamic user-optimal model for a polycentric urban city

Abstract: A predictive continuum dynamic user-optimal model is extended to investigate the traffic equilibrium problem for a polycentric urban city with multiple central business districts (CBDs). The road network within the city is assumed to be dense and can be viewed as a continuum in which travellers can choose their routes in a two-dimensional space. Travellers are assumed to choose their route to minimise the actual total cost to the destination (i.e. the CBD). The model consists of two parts: the conservation law part and the Hamilton–Jacobi part. The finite volume method is used to solve each part on unstructured meshes. Because the two parts are closely interconnected and have different initial times, solving the model can be treated as a fixed-point problem, which is solved using a self-adaptive method of successive averages. Numerical experiments for an urban city with two CBDs are presented to demonstrate the effectiveness of the model and the numerical algorithm.

Optimal velocity model with dual boundary optimal velocity function

Abstract: This paper proposes a dual boundary optimal velocity model (DBOVM) by substituting a dual boundary optimal velocity function (DBOVF) for the original one in the optimal velocity model. The speed adjustment mechanism is introduced to describe the rule of car-following within the dual boundary steady region. Field data are studied, which verify the assumption of DBOVM. Properties of traffic state transition in the law of DBOVM are analysed. Besides, the dynamic properties and the stability of DBOVM are studied by means of numerical simulations. It is found that the DBOVM can describe the capacity drop and hysteresis loop phenomena quite well. The stability of DBOVM is found related to the initial conditions on both boundaries of DBOVF. The speed adjustment mechanism has positive effect on the stability of DBOVM.

A novel agent-based modelling framework for travel time reliability analysis

Abstract: Under transportation network supply and demand uncertainty, travel time reliability emerges from non-linear interactions among numerous travellers who are driven by self-interest, learn and adapt in changing situations, and therefore can be modelled as an emergent network property. This paper proposes a novel theoretical framework for the study of complexity regarding travel time reliability on the basis of empirically derived individual decision rules, and develops an agent-based evolutionary model for travel time reliability analysis. Findings show that actual route choice behaviours related to network reliability are often non-optimal, and that these behaviours themselves are important determinants of travel time reliability under network supply and demand uncertainty. While many travellers search for alternative routes under uncertainty, few travellers actually change routes. Route choice rules employed by travellers can successfully improve travel time reliability in most tested uncertainty scenarios...

Travel time variations over time and routes: endogenous congestion with degradable capacities

Abstract: To investigate how the travel time variability develops over time and routes, in relation to mean travel time, this paper analytically explores the departures with day-to-day capacity variations. C...

Linking a transport dynamic model with an emissions model to aid air pollution evaluations of transport policies in Latin America

Abstract: Considering the key role of the transport sector in the economy and its contribution to greenhouse gas (GHG) and local air pollutant emissions, the development of integrated techniques to evaluate long-term urban trends should be a top priority for creating a more sustainable society. This paper presents an integrated model for reliable estimation of passenger transport emissions of local pollutants and CO2 using an integrated Land-Use and Transport Interaction (LUTI) model in Bogota (Colombia) between 2010 and 2026. Two additional scenarios are modelled to illustrate the use of the model to evaluate the impacts of possible policy interventions. An alternative system dynamics approach is proposed as part of a structured decision-making process. The methodology uses causal loop diagrams (CLD) from systems dynamics to explain cause-and-effect relations, through linking the transport emissions and transport subsystems. The emissions model considers 11 different vehicle categories in total and emissio...

Observations on the fundamental diagram and their interpretation from the human factors perspective

Abstract: Some observations are made on the fundamental diagram of freeway traffic,among which are three influence regions, three types of transition around capacity, and a capacity drop phenomenon. This research aspires to interpret these observations from the human factors perspective in traffic flow theory. A combination of these factors shapes the above-mentioned influence regions, transition around capacity, and capacity drop. Of critical importance in determining the transition around capacity and capacity drop is drivers' aggressiveness, a factor that has long been overlooked in the past. This paper provides a detailed account of where it comes from and how it influences the fundamental diagram.

Revisiting distribution model of departure headways at signalised intersections

Abstract: The departure headway is one of the critical parameters to optimise and evaluate the design and timing of signalised intersections. In order to provide a suitable method to accurately estimate saturation headway at signalised intersections, the distribution of departure headways and its characteristics were investigated based on field observation in Shanghai, China. Statistical analysis results reveal that (1) Shifted Log-Normal distribution can be used to capture the features of departure headways distribution at each position in a queue, including headways at the first position which are usually excluded in existing models; (2)Shifted Log-Normal is more suitable to capture the distribution of steady-flow headways which are approximately the headways at positions between the fifth vehicle and the last stopping vehicle in the queue; (3) the mode of steady-flow headway distribution, which reflects the real manipulative ability of drivers in a certain region, can be considered as theoretical saturation head...

Exploring the differences in the airport competitiveness formation mechanism: evidence from 45 Chinese airports during 2010–2014

Abstract: In this paper, the formation mechanism difference for airport groups is explored. The 45 Chinese airports operating from 2010 to 2014 are classified into 3 groups by a K-means clustering algorithm. Then, the formation mechanism index system is built using seven aspects: Regional Development, Infrastructure Conditions, Operational Strength, Demand Conditions, Support Industry, Service Strength and Technology Index. The formation mechanisms of the 3 airport groups are tested based on 11 basic hypotheses. The results show that different airport groups have different competitiveness formation mechanisms. The conclusions can provide targeted competitiveness cultivation guidance for decision makers at different airports.

A trip-chain-based combined mode and route-choice network equilibrium model

Abstract: This paper proposes a trip-chain-based mode and route-choice network equilibrium model that considers the ‘common lines problem’ in transit assignment. The proposed model assumes the nested-logit type of mode and route-choice structure for the travellers’ mode and route choice. The proposed model is formulated using the variational inequality problem, and the relaxation method is applied to solve the proposed model. Finally, the proposed model is applied to hypothetical networks, and confirms that the differences in the total mode share, link flows, and link travel times between the proposed model and the traditional trip-based assignment model are not large. We also confirmed that the some trip-chains differed considerably in mode share.

A multi-agent learning approach for online calibration and consistency checking of real-time traffic network management systems

Abstract: Considerable effort has been devoted to developing real-time traffic network management systems for congestion mitigation in large metropolitan areas. These systems usually adopt high-resolution simulation models to provide real-time traffic network state estimation and short-term prediction capabilities. If the simulation results deviate from their corresponding real-world observations, online adjustment to the parameters of the simulation model is recommended to maintain its consistency. For that purpose, several consistency checking and online adjustment modules could be integrated with the simulation model and activated periodically to maintain the model consistency. This paper presents a multi-agent learning methodology for consistency checking and online calibration of real-time traffic network simulation models. The methodology allows multiple online adjustment modules to learn based on their historical performance. Consequently, an adjustment module is activated only if its activation is e...

Interdependences between current choices and future expectations in the context of Hanoians’ residential location choices

Abstract: Based on the theory of backward-looking and forward-looking behaviour, a residential location choice model is established to represent interdependences between current choices and future expectations (FE). The interdependences might be observed not only with respect to a particular alternative in a choice set (within-alternative interdependences), but also between different alternatives (between-alternative interdependences), which are jointly incorporated by using a paired combinatorial logit model. Analysis results using data collected from 13,712 individuals in Hanoi in 2005 confirmed that 26.42–55.28% of the total variance of current residential location choice utility can be explained by FE, while 40.81–99.37% of FE can be captured by current choices (i.e. state dependence). The influence of within-alternative interdependences regarding urban core (UC) residence for low-income individuals is almost double that for medium-to-high-income individuals. For between-alternative interdependences, si...

Trade-offs among planned versus performed activity patterns

Abstract: This paper focuses on the development of a methodology to identify the latent factors leading to changes in the planned itineraries of travellers that result in their actual activity patterns. Specifically, we propose a way to utilise patterns of activities established by individuals across multiple days to generate possible alternative actions by these individuals when faced with conditions that produce a discrepancy between performed and planned patterns on a particular day. The choice alternatives, which are unobserved, are inferred by rules applied to comprehensive multiday data collected in Belgium, consisting of information regarding planned activity itineraries, performed activity/travel diaries, and demographics of travellers. These data are utilised to analyse and explore the underlying reasons preventing individuals from performing their planned activities on a given day, and to identify the influential parameters that lead individuals to trade their planned patterns with those actually ...

Clustering route choices methodology for network performance analysis

Abstract: The Network Macroscopic Fundamental Diagram (NMFD) provides a quick overlook of a network performance. Recent studies show that inhomogeneous density spatial distributions significantly reduce the network efficiency. However, few studies investigate the triggers of such distributions. In this paper, we investigate how route choices influence the level of performance of a network and we propose a complete methodology to analyse such a relationship. To simplify the exploration, route choice alternatives are clustered in homogeneous groups with respect to the percentage of overlapping and a large set of flow distribution among routes is tested. The investigations are conducted using both analytical formulations and simulation techniques based on a mesoscopic traffic flow simulator. Analytical formulations define the boundary between fluid and congested network loading. The sensitivity to route choices is then assessed. Then, route choice effects on the network level of performance is quantified using...