Calibration and validation of a shared space model: case study

Shared space is an innovative streetscape design that seeks minimum separation between vehicle traffic and pedestrians. Urban design is moving toward space sharing as a means of increasing the community texture of street surroundings. Its unique features aim to balance priorities and allow cars and pedestrians to coexist harmoniously without the need to dictate behavior. There is, however, a need for a simulation tool to model future shared space schemes and to help judge whether they might represent suitable alternatives to traditional street layouts. This paper builds on the authors’ previously published work in which a shared space microscopic mixed traffic model based on the social force model (SFM) was presented, calibrated, and evaluated with data from the shared space link typology of New Road in Brighton, United Kingdom. Here, the goal is to explore the transferability of the authors’ model to a similar shared space typology and investigate the effect of flow and ratio of traffic modes. Data recorded from the shared space scheme of Exhibition Road, London, were collected and analyzed. The flow and speed of cars and segregation between pedestrians and cars are greater on Exhibition Road than on New Road. The rule-based SFM for shared space modeling is calibrated and validated with the real data. On the basis of the results, it can be concluded that shared space schemes are context dependent and that factors such as the infrastructural design of the environment and the flow and speed of pedestrians and vehicles affect the willingness to share space

Wide area DGPS and fiducial network design

SIGLEAvailable from British Library Document Supply Centre- DSC:DX177988 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Modelling shared space users via rule-based social force model

The promotion of space sharing in order to raise the quality of community living and safety of street surroundings is increasingly accepted feature of modern urban design. In this context, the development of a shared space simulation tool is essential in helping determine whether particular shared space schemes are suitable alternatives to traditional street layouts. A simulation tool that enables urban designers to visualise pedestrians and cars trajectories, extract flow and density relation in a new shared space design, achieve solutions for optimal design features before implementation, and help getting the design closer to the system optimal. This paper presents a three-layered microscopic mathematical model which is capable of representing the behaviour of pedestrians and vehicles in shared space layouts and it is implemented in a traffic simulation tool. The top layer calculates route maps based on static obstacles in the environment. It plans the shortest path towards agents’ respective destinations by generating one or more intermediate targets. In the second layer, the Social Force Model (SFM) is modified and extended for mixed traffic to produce feasible trajectories. Since car movements are not as flexible as pedestrian movements, velocity angle constraints are included for cars. The conflicts described in the third layer are resolved by rule-based constraints for shared space users. An optimisation algorithm is applied to determine the interaction parameters of the force-based model for shared space users using empirical data. This new three-layer microscopic model can be used to simulate shared space environments and assess, for example, new street designs

Approach for evaluating the safety of a satellite-based train localisation system through the extended integrity concept

ESREL 2015 - European safety and reliability conference, Zürich, SUISSE, 07-/09/2015 - 10/09/2015The integrity concept, safety quality criterion for satellite-based localisation systems used in aeronautics, is described in terms of levels (protection and alert levels), time (Time To Alarm) and probability (integrity risk). In land transport applications, the requirements in terms of integrity differ from aeronautics in their definition and values. Global Navigation Satellite Systems (GNSS) in railways suffer from additional weaknesses i.e. multipath and masking phenomena, which can degrade the localisation integrity. This situation cannot be tolerated in safety-related applications like train control and signalling. To mitigate these weaknesses, GNSS is usually combined with other localisation systems like inertial sensors. However, existing integrity monitoring processes are designed for GNSS integrity evaluation, i.e. to estimate the risk allocated to the position given by the GNSS receivers only. Our research work aims, first, to extend the integrity concept to such systems, and, secondly, to demonstrate how to evaluate, with this concept, the safety of a localisation system as expected in railways. The safety of GNSS-Based Localisation System is formalised and quantitatively evaluated.Le concept d'intégrité, critère de sécurité pour les systèmes de localisation par satellite utilisés dans l'aéronautique, est décrite en termes de niveaux (niveaux de protection et d'alerte), le temps (temps d'alerte) et la probabilité (risque d'intégrité). Dans les applications de transport terrestre, les exigences en termes d'intégrité diffèrent de l'aéronautique dans leur définition et des valeurs. Les Global Navigation Satellite Systems (GNSS) dans le domaine ferroviaire souffrent de faiblesses supplémentaires telles que des phénomènes de multitrajets et de masquage, qui peuvent dégrader l'intégrité de la localisation. Cette situation ne peut être tolérée dans des applications liées à la sécurité, comme le contrôle/commande des trains et la signalisation. Pour atténuer ces faiblesses, le GNSS est généralement combiné avec d'autres systèmes de localisation comme des capteurs inertiels. Toutefois, les processus de surveillance de l'intégrité existants sont conçus pour l'évaluation de l'intégrité du GNSS, soit pour estimer le risque attribué à la position donnée par les récepteurs GNSS seulement. Notre travail de recherche vise, d'abord, à étendre le concept de l'intégrité de ces systèmes, et, d'autre part, à démontrer comment évaluer, avec ce concept, la sécurité d'un système de localisation comme attendu dans le domaine ferroviaire. La sécurité d'un système de localisation basé sur les GNSS est formalisée et quantitativement évaluée