John W. Polak

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Quasi-random number sequences have been used extensively for many years in the simulation of integrals that do not have a closed-form expression, such as Mixed Logit and Multinomial Probit choice probabilities. Halton sequences are one example of such quasi-random number sequences, and various types of Halton sequences, including standard, scrambled, and(More)
In this paper, we discuss some of the issues that arise with the computation of the implied value of travel-time savings in the case of discrete choice models allowing for random taste heterogeneity. We specifically look at the case of models producing a non-zero probability of positive travel-time coefficients, and discuss the consistency of such estimates(More)
Vehicular Ad hoc NETworks (VANETs) is a subclass of Mobile Ad hoc NETworks (MANETs). However, automotive ad hoc networks will behave in fundamentally different ways than the predominated models in MANET research. Driver behaviour, mobility constraints and high speeds create unique characteristics in the network. All of these constraints have implications on(More)
The Mobile Environmental Sensor System Across GRID Environments (MESSAGE) project is a research project co-funded by EPSRC and the Department for Transport. The project was funded as part of the e-Science initiative with the aim of demonstrating that key outcomes from that programme could be deployed to address real world issues, in this case the detailed(More)
The space and time dynamics of moving vehicles regulated by traffic signals governs the node connectivity and communication capability of vehicular ad hoc networks (VANETs) in urban environments. However, none of the previous studies on node connectivity has considered such dynamics with the presence of traffic lights and vehicle interactions. In fact, most(More)
The analysis of air-passengers’ choices of departure airport in multi-airport regions is a crucial component of transportation planning in many large metropolitan areas, and has been the topic of an increasing number of studies over recent years. In this paper, we advance the state of the art of modelling in this area of research by making use of a(More)
The majority of studies of air travel choice behavior make use of Revealed Preference (RP) data, generally in the form of survey data collected from departing passengers. While the use of RP data has certain methodological advantages over the use of Stated Preference (SP) data, major issues arise because of the often low quality of the data relating to the(More)
In this paper, we analyze the connectivity dynamics of vehicular ad-hoc networks in a generic signalized urban route. Given the velocity profile of an urban route as a function of space and time, we utilize a fluid model to characterize the general vehicular traffic flow, and a stochastic model to capture the randomness of individual vehicle. From the fluid(More)