David Watling

• BSc, PhD
• Professor at University of Leeds

In spite of their widespread use in policy design and evaluation, relatively little evidence has been reported on how well traffic equilibrium models predict real network impacts. Here we present what we believe to be the first paper that together analyses the explicit impacts on observed route choice of an actual network intervention and compares...

Selfish routing, represented by the User-Equilibrium (UE) model, is known to be inefficient when compared to the System Optimum (SO) model. However, there is currently little understanding of how the magnitude of this inefficiency, which can be measured by the Price of Anarchy (PoA), varies across different structures of demand and supply. Such und...

Analysing the repeated trip behaviour of travellers, including trip frequency and intrapersonal variability, can provide insights into traveller needs, flexibility and knowledge of the network, as well as inputs for models including learning and/or behaviour change. Data from emerging data sources provide new opportunities to examine repeated trip...

Stochastic User Equilibrium (SUE) models allow the representation of the perceptual and preferential differences that exist when drivers compare alternative routes through a transportation network. However, as an effect of the used choice models, conventional applications of SUE are based on the assumption that all available routes have a positive...

The potential of passively generated big data sources in transport modelling is well‐recognised. However, assessing their accuracy and suitability for policymaking remains challenging due to the lack of ground‐truth (GT) data for validation. This study evaluates the accuracy of inferring human mobility patterns from global positioning system (GPS),...

Most choice models, e.g. Multinomial Logit (MNL), rely on random utility theory, which assumes that a compensatory utility maximization decision rule explains an individual’s choice behaviour. Research has shown, however, that behaviour is sometimes better explained by non-compensatory decision rules. While some research has used Latent Class Choic...

Network equilibrium models have been extensively used for decades. The rationale for using equilibrium as a predictor is essentially that (i) a unique and globally stable equilibrium point is guaranteed to exist and (ii) the transient period over which a system adapts to a change is sufficiently short in time that it can be neglected. However, we f...

Aggregated mobility indices (AMIs) derived from information and communications technologies have recently emerged as a new data source for transport planners, with particular value during periods of major disturbances or when other sources of mobility data are scarce. Particularly, indices estimated on the aggregate user concentration in public tra...

Modeling Mobility-on-Demand (MoD) services is important from a regulatory perspective, and requires 11methods to capture the equilibrium of MoD systems. While there exists a large body of literature on MoD services focusing on service design under equilibrium modeling for given demand and operational policies, such policies might not be readily kno...

The road user network is a dynamic, ever-evolving population in which road users interact to share and compete for road space. The advent of autonomous road vehicles (ARVs) will usher in numerous opportunities and challenges in road user dynamics. One of the challenges is whether an ARV population would be able to successfully enter the existing ro...

Bounded Path Size (BPS) route choice models (Duncan et al, 2021) offer a theoretically consistent and practical approach to dealing with both route overlap and unrealistic routes. It captures correlations between overlapping routes by including correction terms within the probability relations, and has a consistent criterion for assigning zero prob...

Multimodal travel behaviour, also termed multimodality, refers to as the phenomenon of an individual using more than one mode of transport in a given period. Studies indicate that encouraging multimodality may provide a solution to induce modal shifts towards sustainable transport. In this research, we investigate the distribution of mode-specific...

We consider optimizing a truck's choice of path and speed profile to minimise fuel consumption, exploiting real-time predictive information on dynamically varying traffic conditions. Time-varying traffic conditions provide particular challenges, both from network-level interactions (e.g. slowing to consume more fuel locally may be beneficial to avo...

Increasingly, demanding environmental standards reflect the need for improved energy efficiency and reduced externalities in the transportation sector. Reference driving cycles provide standard speed profiles against which future developments and innovations may be tested. In the paper, we develop such profiles for a class of electric L-category ve...

The advent of highly automated vehicles in the form of autonomous road vehicles (ARVs) is bound to bring about a paradigm shift in road user interaction, especially that between ARVs and human-driven vehicles (HDVs). Previous literature on the game-theoretic interaction between ARVs and HDVs tends to focus on working out the best possible strategy...

The Stochastic User Equilibrium (SUE) traffic assignment model is a well-known approach for investigating the behaviours of travellers on congested road networks. SUE compensates for driver/modelling uncertainty of the route travel costs by supposing the costs include stochastic terms. Two key challenges for SUE modelling, however, are capturing ro...

Wireless charging technologies have now made it possible to charge while driving, which offers the opportunity to stimulate the market penetration of electric vehicles. This paper aims to support the system planner in optimally deploying the wireless charging lanes on the network, considering traffic dynamics and congestion under multiple vehicle c...

Reducing stationary or very slowly moving queues is one way of reducing congestion, pollution, inefficient stop–start travel and carbon emissions in cities. This paper considers traffic signal control and road pricing together; aiming to eliminate queueing in at least a subnetwork. Link-exit green-times and link-exit bottleneck delays are considere...

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...

Multimodality refers to the phenomenon of using more than one mode of transport in a given period. Encouraging multimodality potentially provides an effective solution to reduce CO2 emissions and induce modal shifts toward sustainable transport. This research investigates the extent to which the level and correlates of multimodality differ by trip...

This study aims to seek the optimal deployment of fast-charging stations concerning the traffic flow equilibrium and various realistic considerations to promote Electric Vehicles (EVs) widespread adoption. A bi-level optimization framework has been developed in which the upper level aims to minimize the total system cost (i.e., capital cost, travel...

Sustainable urban mobility is an essential component of sustainable development but requires careful planning in rapidly growing urban areas. This paper investigates the value and limitations of Big Data for evaluating transport policies, plans, and projects in Hubballi‐Dharwad, India. Results show how Big Data can enable the outcomes of transport...

The predictive cruise control (PCC) is a promising method to optimize energy consumption of vehicles, especially the heavy-duty vehicles (HDV). Due to the limited sensing range and computational capabilities available on-board, the conventional PCC system can only obtain a sub-optimal speed trajectory based on a shorter prediction horizon. The rece...

The availability of newly emerging forms of data in recent years has provided new opportunities to study spatial intrapersonal variability, namely the variability in an individual’s destination and route choices from day to day. As well as providing insights into traveller needs, preferences and adaptive capacity, spatial intrapersonal variability...

This paper develops a new route choice modelling framework that deals with both route correlations and unrealistic routes in a consistent and robust way. To do this, we explore the integration of a correlation-based Path Size Logit model with the Bounded Choice Model (BCM) (Watling et al, 2018). We find, however, that the natural integration of the...

Although the electrification of transportation can bring long-term sustainability, increasing penetration of Electric Vehicles (EVs) may cause more congestion. Inappropriate deployment of charging stations not only hinders the EVs adoption but also increases the total system costs. This paper attempts to identify the optimal locations for fast-char...

One of the actions usually conducted to limit exposure to a hazardous event is the evacuation of the area that is subject to the effects of the event itself. This involves modifications both to demand (a large number of users all want to move together) and to supply (the transport network may experience changes in capacity, unusable roads, etc.). In...

Studies of the effect of network structure on performance have, thus far, been restricted to examining ensembles of synthetic networks generated by canonical models from the Network Science literature, which do not plausibly represent real road networks. Furthermore disparate ranges of parameter settings for demand and supply structure are often us...

Dynamic traffic assignment (DTA) is an important method in the long term transportation planning and management processes. However, in most existing system optimum dynamic traffic assignment (SO-DTA), no side constraints are used to describe the dynamic link capacities in a network which is shared by multiple vehicle types. Our motivation is based...

Automated Guided Vehicles are increasingly used for material transfer in factory and warehouse environments amongst humans and human operated vehicles. Safe and efficient operation is challenging when there is a mix of human and automated traffic as fixed guide paths can become blocked more frequently. In this work we aim to show smooth and efficie...

Multimodality – the behavioural phenomenon of using multiple modes of transport – has been suggested to be a useful indicator of an individual’s willingness to adopt more sustainable transport alternatives. Analysing temporal patterns in multimodality provides the opportunity to understand the formation of multimodal practices. Yet the existing stu...

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...

Inappropriate deployment of charging stations not only hinders the mass adoption of Electric Vehicles (EVs) but also increases the total system costs. This paper attempts to address the problem of identifying the optimal locations of fast-charging stations in the urban network of mixed gasoline and electric vehicles with respect to the traffic equi...

Path Size Logit route choice models attempt to capture the correlation between routes by including correction terms within the route utility functions. This provides a convenient closed-form solution for implementation in traffic network models. The path size terms measure distinctiveness of routes; a route is penalised based on the number of other...

A method is presented for the real-time optimal control of the journey of a truck, travelling between a pair of pick-up/drop-off locations in a time-varying traffic network, in order to reduce fuel consumption. The method, when applied during the journey, encapsulates the choice of route, choice of speeds on the links, and choice of stop locations/...

Embedded within the vehicle "routing" problem of determining the order in which customers are served, is the route choice problem of which sequence of roads to use between a pair of pick-up/drop-off locations, and this latter is the focus of the paper. When the objective is something other than travel time, such as fuel consumption, an additional c...

Stability of equilibria in transport systems has been discussed for decades. Even in deterministic cases, where stochasticity is ignored, stability is not a general property; a counterexample has been found in (within-day) dynamic traffic assignment problems. Instability can be a source of uncertainty of travel time and although pricing may stabili...

It is well known that uniqueness and stability are guaranteed properties of traffic equilibria in conventional user-equilibrium traffic assignment problems, if the link travel utilities are assumed to be strictly monotonically decreasing with respect to the link traffic volumes. However, these preferable properties do not hold in a wide range of tr...

Highly automated vehicles operating at SAE automation level 4 and 5 will not require the occupants’ attention to be on the road at all. They will be free to amuse themselves as passengers. This will have the side effect of making them more vulnerable to motion sickness. Automated vehicles must plan paths which are feasible for the vehicle and comfo...

The accurate depiction of the existing traffic state on a road network is essential in reducing congestion and delays at signalized intersections. The existing literature in the optimization of signal timings either utilizes prediction of traffic state from traffic flow models or limited real-time measurements available from sensors. Prediction of...

Stability of equilibria in transport systems has been discussed for decades. Even in deterministic cases where stochasticity is ignored, stability is actually not a general property as a counterexample has been found in (within-day) dynamic traffic assignment problems. Instability can be a source of uncertainty of travel time. Although pricing may...

Dynamic traffic assignment (DTA) is an important method in the long term transportation planning and management processes. However, in most existing system optimum dynamic traffic assignment (SO-DTA), no side constraints are used to describe the dynamic link capacities in a network which is shared by multiple vehicle types. This paper proposes a no...

We consider a wide class of stochastic process traffic assignment models that capture the day-to-day evolving interaction between traffic congestion and drivers’ information acquisition and choice processes. Such models provide a description of not only transient change and ‘steady’ behaviour, but also represent additional variability that occurs t...

This paper studies first-best and second-best congestion pricing in the presence of unobserved and observed preference heterogeneity using a stylised stochastic user equilibrium choice model. Travellers choose between multiple alternatives, have heterogeneous values of travel times, and may differ in their valuation of variety. We derive first-best...

The effects of day-today variability in travel behaviour are visible on all transport networks, for example in the form of travel time unreliability on road networks. Understanding variability in travel behaviour matters when allocating resources on networks, developing suitable policies and including variability in models. Quantitative analyses re...

This paper considers the implications of so-called ‘big data’ for the analysis, modelling and planning of transport systems. The primary conceptual focus is on the needs of the practical context of medium-term planning and decision-making, from which perspective the paper seeks to achieve three goals: (i) to try to identify what is truly ‘special’...

The final open access printed version is available at: http://www.tandfonline.com/doi/full/10.1080/15568318.2017.1368748 We propose a novel method to estimate capability to make bicycle journeys, specifically considering the individual physical capability (IPC) of entire populations of individuals from all population segments of an area, not just...

We propose a hybrid static spatial microsimulation technique that combines simulated annealing and synthetic reconstruction (Monte-Carlo sampling), in order to generate a synthetic population of individuals as part of a model-based policy indicator. We focus on the following case: (i) the model, must produce outputs at a fine spatial resolution; (i...

It is well known that traffic flows in road networks may vary not only within the day but also between days. Existing models including day-to-day variability usually represent all variability as unpredictable fluctuations. In reality, however, some of the differences in flows on a road may be predictable for transport planners with access to histor...

The traditional equilibrium approach for traffic assignment and transportation planning provides a description of a self- consistent state of the transportation network, which it is assumed would arise if network characteristics (such as roadway capacity, link performance functions) and travel demand were to remain unchanged for an extended period...

This paper presents the application and calibration of the recently proposed Restricted Stochastic User Equilibrium with Threshold model (RSUET) to a large-scale case-study. The RSUET model avoids the limitations of the well-known Stochastic User Equilibrium model (SUE) and the Deterministic User Equilibrium model (DUE), by combining the strengths...

This paper presents a general modelling approach to day-to-day dynamic assignment to a congested network through discrete-time stochastic and deterministic process models including an explicit modelling of users’ habit as a part of route choice behaviour, through an exponential smoothing filter, and of their memory of network conditions on past day...

Real-life systems are known to exhibit considerable day-to-day variability. A better understanding of such variability has increasing policy-relevance in the context of network reliability assessment and the design of intelligent transport systems. Conventional equilibrium models are ill-suited, because deterministic models such as these do not acc...

We consider the modelling of road transport systems as a day-to-day dynamic, deterministic process. The main contribution is to present a unified treatment of discrete-time and continuous-time approaches, with these two classes of approaches having been developed in two parallel streams of research which have had little connection made between them...

Accurate depiction of existing traffic states is essential to devise effective real-time traffic management strategies using Intelligent Transportation Systems (ITS). Existing applications of Dynamic Traffic Assignment (DTA) methods are mainly based on either the prediction from macroscopic traffic flow models or measurements from the sensors and d...

The objective of current paper is to provide an impressionistic overview of 19 papers, taken from academic journals, that narrate histories of urban transport, and to consider how insights from this overview might be used in the construction of narratives of future urban transport. The selected papers provide narratives of specific cities as well a...

The Deterministic and Stochastic User Equilibrium (DUE and SUE) have limitations by allowing only minimum cost routes to be used in the DUE and requiring all routes to be used in SUE. The Restricted SUE (RSUE) was proposed to remove these limitations and facilitate large‐scale application. The RSUE use random utility maximisation models for flow al...

The aim of this paper is to remove the known limitations of Deterministic and Stochastic User Equilibrium (DUE and SUE), namely that only routes with the minimum cost are used in DUE, and that all permitted routes are used in SUE regardless of their costs. We achieve this by combining the advantages of the two principles, namely the definition of u...

This paper presents a day-to-day dynamic analysis of mode choice behaviour in a transportation system. Presented results, regarding a simple two-mode system, support the conjecture that multiple equilibria can likely be observed in such systems. This condition may have a great impact on the design of transit operator strategies.

Macroscopic or flow-based dynamic traffic assignment (DTA) models normally treat traffic in each direction on a roadway as a single lane and, since they do not consider multiple lanes, they can not consider lane-changing behaviour. To investigate how the results may be affected by explicitly considering lanes and lane changing, we consider a road l...

We review and advance the state-of-the-art in the modelling of transportation systems as a stochastic process. The conceptual and theoretical basis of the approach is explained in detail. A variety of examples are given to motivate its use in the field. While the examples cover a wide range of modelling philosophies, in order to provide focus they...

There is extensive empirical evidence that travellers consider many 'qualities' (travel time, tolls, reliability, etc.) when choosing between alternative routes. Two main approaches exist to deal with this in network assignment models: Combine all qualities into a single (linear) utility function, or solve a multi-objective problem. The former has...

The key thesis underlying the present paper is that, at the current time, more imaginative approaches could be used for thinking about the future than those used in traditional forecasting exercises. It is argued that the latter make essentialist assumptions about human travel behavior, and typically extrapolate present circumstances to the future...

There is extensive empirical evidence that travellers consider many qualities (travel time, tolls, reliability, etc.) when choosing between alternative routes. Two main approaches exist to deal with this in network assignment models: Combine all qualities into a single (linear) utility function, or solve a multi-objective problem. The former has th...

While there exists extensive literature on the first- and second-best tolling of congested transportation networks, much of it presumes the existence of a single agent responsible for toll-setting. The present paper extends the small but growing body of work studying the impact of several agents independently regulating tolls on different parts of...

Accurate depiction of existing traffic states is essential to devise effective real-time traffic management strategies using Intelligent Transportation Systems (ITS). Existing applications of Dynamic Traffic Assignment (DTA) methods are mainly based on either the prediction from macroscopic traffic flow models or measurements from the sensors and d...

Transport planners face a major challenge to devise policies to meet multiple expectations and objectives. While we know that transport networks are complex, multi-modal, and spatially distributed systems, there is now a long history of mathematical tools which assist planners in understanding travel movements. However, the objectives that they are...

Considering transport networks, is network structure important? Some questions that arise: 1. What structure do these networks have? 2. Is network structure/topology important? 3. Is it meaningful to compare different networks, and their performance? 4. Can we understand anything about transferability e.g. of a transport policy? 5. Are there common...

A novel approach to estimating a population " s capacity to travel by walking and cycling (also referred to as active modes) is presented. Estimating capacity to walk and cycle is distinct from predicting future walking and cycling behaviour based upon current behaviour. Capacity is useful in developing anticipatory policy responses to transport sc...

Short-term congestion caused due to traffic incidents or other road environment factors significantly reduces traffic flow capacity of a link which forms a major part of travel time delays. Accurate and reliable estimate of real-time traffic state is essential for optimizing network performance during unpredictable events. Inaccurate estimate of cu...

This article proposes a maximum-likelihood method to update travel behavior model parameters and estimate vehicle trip chain based on plate scanning. The information from plate scanning consists of the vehicle passing time and sequence of scanned vehicles along a series of plate scanning locations (sensor locations installed on road network). The a...

Travellers’ behaviours in transport systems depend on various types of interactions among users and hence, in addition to understanding individual travel behaviour, it is necessary to analyse these interactions to understand properties of a transport system. There are two types of interactions. Traditionally, transport studies have dealt with inter...

In traffic assignment models with time-varying flows (dynamic network loading or dynamic traffic assignment), overtaking behaviour is normally not included in the model and, in that case, it is important that the model at least approximates first-in–first-out (FIFO), to prevent deviations from FIFO that are arbitrary or unrealistic or not physicall...