Fully Distributed Traffic Information Systems (fdtis) are based on vehicle-to-vehicle wireless data transmission that enables traffic self-organization. For instance, alert messages transmitted by vehicles in poor traffic conditions allow receivers to avoid congested roads and reduce travel time. Such systems are of great practical interest and may provide excellent results in urban conditions due to the presence of numerous potential partners for most vehicles. Unfortunately, many applications already use the wireless transmission medium in cities, leading to frequent problems with saturation. In order to avoid such issues, fdtis must generate as few transmissions as possible, while remaining effective. In the specific context of congestion avoidance, we present a method that improves the efficiency of traffic alert messages by directing them to the geographic regions where they are most useful. This method uses past trajectory data from the vehicles involved in a traffic jam, thus decreasing the number of messages. We compared the performance of our method in simulation to a reference implementation and showed that, in the case of intensive traffic, this method prevents saturation of the wireless medium which would have resulted in a general degradation in performance. From a macroscopic point of view, we also showed that the improvement in medium usage obtained had no impact on the ability of our system to ease traffic jams.

Distributed, cooperative systems dedicated to road traffic self-organization are very attractive, but present some drawbacks. In particular, their cooperative nature makes them fairly inefficient when working with a reduced number of partners. This situation typically corresponds to the deployment stage, during which only a few vehicles cooperate. This time period cannot be avoided when pushing a new system to the market. We are interested in two features that are important for this kind of system: traffic jam detection and traffic alert transmission. For the first feature, we present a theoretical model that anticipates the proportion of equipped vehicles that allows an acceptable level of traffic jam detection, and we validate this model by simulation. For the second feature, we examine two ways to improve the system behaviour when the proportion of equipped vehicles is very low; their efficiency is tested through simulation. This study is innovative because the simulation platform we developed can take into account the directional behaviour of wireless communications in urban context for a low computational cost. (C) 2012 Elsevier B.V. All rights reserved.

Based on traffic data acquisition by the vehicles and inter-vehicle wireless communications, road traffic self-organization has been studied for several years. In this paper we propose a generic model of cooperation among vehicles, which is designed not to saturate the communication medium and to be insensitive to information loss among vehicles. We also propose an original software simulator, which helps us to show how this model can be used in realistic traffic situations. In the simulation, we evaluate one instance of our model, which features an algorithm for limiting the risks of information storms. This feature is particularly interesting in urban settings, where radio communication must fit within the traditional IEEE-802.11 traffic. We show that this algorithm can considerably reduce the amount of communication, without affecting the quality of traffic self-organization.

In this paper, we show how to deform a planar rational cubic based on a local interpolation constraint while retaining the qualitative shape of the curve. An impedance-type, parallel haptic device is used to signal changes of the number of inflection points, cusps and loops during the deformation. In this way, the user is provided with an intuitive and natural guidance throughout the curve's shape generation process in CAD.

Based on traffic data acquisition by the vehicles themselves, road traffic self-organization has been studied for several years. Geolocation equipment is now available at an affordable cost. With the IEEE-802.11p standard, wireless inter-vehicle communication is of age. This explains current interest for this subject, the practical applications being immediate.

Linda is an elegant parallel and distributed programming model. It is based on a shared associative memory, structured in tuples. We show in this paper that this model suffers from the false matching phenomenon. We explain under which conditions this problem occurs, we examine the solutions already proposed to solve it, and we show why they are not sufficient. In this framework, our goal is to propose an extension to the Linda model in order to eliminate the false matching phenomenon. This model-Linda with bound types or B-Linda-suitable for modern programming paradigms, adds an extended-type notion into the basic Linda model. It is first introduced in an informal manner, then we present an implementation of it. Some formal aspects are specified in the appendix: The definition of the model's elements and operational semantics.