Ioannis Kaparias

A New Measure of Travel Time Reliability for In-Vehicle Navigation Systems

This article introduces a new measure of travel time reliability for implementation in the dynamic routing algorithm of an intelligent car navigation system. The measure is based on the log-normal distribution of travel time on a link and consists of two indices corresponding to the extreme values of the distribution, such that they reflect the shortest and longest travel times that may be experienced on the link. Through a series of mathematical manipulations, the indices are expressed in terms of the characteristic values of the speed distribution on the link. An expression relating the indices of a route and the indices of the individual links forming it is derived. The accuracy of the measure is then assessed through a field experiment and the results are presented.

Development and Implementation of a Vehicle–Pedestrian Conflict Analysis Method: Adaptation of a Vehicle–Vehicle Technique

This paper examines the development, use, and evaluation of a new traffic conflict analysis technique that specifically addresses pedestrian–vehicle conflicts with the intention of being applicable to shared-space environments. The method is based on an existing, well-established, and widely used vehicle–vehicle conflict analysis technique, but is adapted to consider the movement of pedestrians, which differs significantly from that of vehicles. The new method is then implemented on the Exhibition Road site of West London with the use of video data collected from locations with a potentially high concentration of vehicle–pedestrian conflicts, and the results of the analysis are presented. Finally, the results are compared with those obtained by other conflict analysis techniques and also against accident data to assess not only the accuracy but also the functionality of the new technique.

Analysis of Pedestrian-Vehicle Traffic Conflicts in Street Designs with Elements of Shared Space

Changes in pedestrian–vehicle traffic conflicts in urban streets redesigned according to the principles of shared space were investigated with a recently developed pedestrian–vehicle conflict analysis (PVCA) method. In a first step, the PVCA method was revised to reflect more accurately the features of shared space; this revision included the definition of a systematic process for identifying conflict occurrences on the one hand and the full quantification of the conflict severity grading process on the other. Then the refined PVCA method was applied to a case study in London with video data from periods before and after the redevelopment of the Exhibition Road site from a conventional dual carriageway to a modern design with some elements of shared space. The results of the comparative analysis indicated a general decrease in traffic conflict rates as a result of the redesign but also highlighted specific issues that may require additional analysis.

Approach to Time Dependence and Reliability in Dynamic Route Guidance

This paper presents a methodology for increasing the reliability of route suggestions in route guidance systems. The procedure, based on the A* path-finding algorithm and Chens link penalty method, involves penalizing links with a high risk of being congested and obtaining a set of reliable route suggestions. Time dependence of travel times is considered by adapting the flow–speed model technique accordingly. The structure of the path-finding algorithms is also modified to account for real road network features. Finally, experiments using simulated travel time and reliability data are carried out on a road network, and the results are discussed.

Adaptive Route Choice Model for Intelligent Route Guidance Using a Rule-Based Approach

A route choice model was devised for personalized route guidance; it can adaptively change its routing function according to the demands of the user. A strategy for personalized route guidance is to incorporate an adaptation process into the route selection rules. In a study, regularities in route selection were discovered by using a rule-based approach, the C4.5 algorithm, which had advantages over other methods because of its comprehendible model structure. The route choice model is combined with a user interface, enabling the efficient collection of user feedback. To examine the adaptability of the model, experiments in which user preferences are predefined and later changed during the tests were carried out. The results of the experiments indicate the applicability of the model in personalized route guidance.

London Congestion Charging: Successes, gaps and future opportunities offered by cooperative ITS

The London Congestion Charging (LCC) scheme was initially introduced on 17 February 2003. Being the largest of its kind and employing advanced technology, it marked a major innovation in the field of urban road user charging and provided inspiration to several other cities worldwide. Nine years on, and following a number of operational changes that have taken place, this study analyzes successes and pitfalls, and identifies potential future opportunities in the light of latest technological developments in the field of cooperative Intelligent Transport Systems (ITS). The analysis concentrates primarily on the LCC scheme itself, but draws broader conclusions about the future of urban road charging in general.

A reliability-based dynamic re-routing algorithm for in-vehicle navigation

This paper presents a new algorithm for a car navigation system, whose purpose is to offer a reliable re-route to the driver in case he/she deviates from the route he/she has been following, or if a traffic incident is reported en route. A reliable route is defined as one that has a low probability of being congested. The new method makes use of the A* route finding algorithm and introduces a link penalizing procedure to avoid unreliable (i.e. potentially congested) and incident-affected links in order to re-route the driver from his/her current position to his/her destination, while constraints are imposed on the route output by the algorithm so as to ensure driver acceptability. The new algorithm, called RDIN-R, is first described and then tested through a simulation experiment on the road network of Munich, Germany.

Reliability Analysis of Road Networks and Preplanning of Emergency Rescue Paths

Emergency vehicles require good access to residences after a large scale disaster. In the Great Hanshin-Awaji Earthquake of January 17, 1995, in the Kobe area of Japan, the access of emergency vehicles to the sites where they were needed was severely hindered by the traffic chaos in the aftermath of the earthquake, obstructing lifesaving activities. The urgent need for improving the reliability of road networks, and especially the reliability of emergency pathways, was thus confirmed.

A dynamic route choice model for public transport networks with boarding queues

Abstract The concepts of optimal strategy and hyperpath were born within the framework of static frequency-based public transport assignment, where it is assumed that travel times and frequencies do not change over time and no overcrowding occurs. However, the formation of queues at public transport stops can prevent passengers from boarding the first vehicle approaching and can thus lead to additional delays in their trip. Assuming that passengers know from previous experience that for certain stops/lines they will have to wait for the arrival of the 2nd, 3rd, …, k-th vehicle, they may alter their route choices, thus resulting in a different assignment of flows across the network. The aim of this paper is to investigate route choice behaviour changes as a result of the formation and dispersion of queues at stops within the framework of optimal travel strategies. A new model is developed, based on modifications of existing algorithms.

Dynamic User Equilibrium in Public Transport Networks with Passenger Congestion and Hyperpaths

This paper presents a Dynamic User Equilibrium for bus networks where recurrent overcrowding results in queues at stops. The route choice model embedded in the dynamic assignment explicitly considers common lines and strategies with alternative routes. As such, the shortest hyperpath problem is extended to a dynamic scenario with capacity constraints where the diversion probabilities depend on the time the stop is reached and on the expected congestion level at that time. In order to reproduce congestion for all the lines sharing a stop, the Bottleneck Queue model with time-varying exit capacity, introduced in Meschini et al. (2007), is extended. The above is applied to separate queues for each line in order to satisfy the First-In-First-Out principle within every attractive set, while allowing overtaking among passengers having different attractive sets but queuing single file.