Mesoscopic simulator data to perform dynamic origin- destination matrices estimation in urban context

The aim of this paper is to explore a new approach to obtain better traffic demand (Origin-Destination, OD matrices) for dense urban networks using traffic simulation data. From reviewing existing methods, from static to dynamic OD matrix evaluation, possible deficiencies in the approach could be identified. To improve the global process of traffic demand estimation, this paper is focusing on a new methodology to determine dynamic OD matrices for urban areas characterized by complex route choice situation and high level of traffic controls. An iterative bi- level approach will be used to perform the OD estimation. The Lower Level (traffic assignment) problem will determine, dynamically, the utilization of the network by vehicles using heuristic data from mesoscopic traffic simulator particularly adapted for urban context. The Upper Level (matrix adjustment) problem will proceed to an OD estimation using optimization least square techniques. In this way, a full dynamic and continuous estimation of the final OD matrix could be obtained. First evaluation of the proposed approach and conclusions are presented

Towards an S-matrix Description of Gravitational Collapse

Extending our previous results on trans-Planckian ($Gs \gg \hbar$) scattering of light particles in quantum string-gravity we present a calculation of the corresponding S-matrix from the region of large impact parameters ($b \gg G\sqrt{s}>\lambda_s$) down to the regime where classical gravitational collapse is expected to occur. By solving the semiclassical equations of a previously introduced effective-action approximation, we find that the perturbative expansion around the leading eikonal result diverges at a critical value $b = b_c = O(G\sqrt{s})$, signalling the onset of a new (black-hole related?) regime. We then discuss the main features of our explicitly unitary S-matrix -- and of the associated effective metric -- down to (and in the vicinity of) $b = b_c$, and present some ideas and results on its extension all the way to the $b \to 0$ region. We find that for $b<b_c$ the physical field solutions are complex-valued and the S-matrix shows additional absorption, related to a new production mechanism. The field solutions themselves are, surprisingly, everywhere regular, suggesting a quantum-tunneling -- rather than a singular-geometry -- situation.Comment: 39 pages, 5 figures; added discussion sect. 7, added references, acknowledgement

Micro-simulation de variantes d'aménagement pour San Sebastian

Le projet traite du remodelage de la structure urbaine du district d'Amara dans la ville de San Sebastian au pays basque espagnol. Amara -et en particulier la place Pio XII située au coeur du district- canalise toute la circulation de transit de la ville à laquelle vient s'ajouter la trafic induit par les centres d'intérêts locaux (bureaux, zones commerciales, tourisme, etc.)

Safety indicators for microsimulation-based assessments

In the field of ITS applications evaluation, micro- simulation is becoming more and more a useful and powerful tool. In the evaluation process, one of the most important steps is the safety analysis. For that purpose, classical micro- simulation outputs give some helpful information, but which aren’t sufficient for an accurate analysis in many cases. Nevertheless, the microscopic level of traffic description offers the possibility of tracking the simulated vehicles getting at each time step their relative position, speed and deceleration. This paper explains how a safety indicator can be calculated with these different parameters. This safety indicator is used in a ramp metering case study to illustrate the utility of such output for a safety analysis. However, this indicator is limited to the linear collision probability and gives therefore no information on crossing trajectories conflicts like in junctions. On the other hand the likelihood of an incident to happen depends not only on traffic conditions but on the influence of many other factors as for example the geometry of the road, the visibility or the pavement conditions (wet, dry, etc.). When significant statistical information is available an estimation of the probability of an incident to happen can be computed, and used in microsimulation analysis. The paper is completed with the development and testing of hierarchical logit based model to estimate this probability