347 research outputs found
Deposition of intact tetrairon(III) single molecule magnet monolayers on gold: an STM, XPS and ToF-SIMS investigation
No full textThe ability of a tetranuclear iron(III) single-molecule magnet functionalized with thioacetyl-terminated ligands to form monolayers on gold has been investigated by a multitechnique approach based on STM, XPS and ToF-SIMS. We discuss in detail several aspects, which are relevant to the reported observation of a memory effect on the monolayer prepared from dichloromethane (Mannini et al., Nat. Mater., 2009, 8, 194). In particular we show that the adsorbate comprises intact surface-bound Fe4 clusters as opposed to microcrystals or multilayers. The influence of the solvent used for the selfassembly process on the morphology, composition and structure of the adsorbate is also studied for four different solvents (dichloromethane, n-hexane, toluene, 1,4-dioxane)
Integrated Variable Speed Limits and User Information Strategy
No full textThis paper deals with the study of variable speed limits (VSLs) for traffic control and their integration with user information strategies. As few studies have addressed the integrated VSL and user information strategy, we focus on comparing the adoption of the latter with the VSL alone strategy application and the no-control case, highlighting the benefits the integration brings. The integrated strategy is able to smooth the severity of congestion, shifting its occurrence in a section of the mainstream mostly suited to vehicle accumulation. An application on a real network is carried out. The traffic congestion conditions along the real highway are simulated by means of Dynameq simulation software and the METANET macroscopic model. The VSLs are applied in a control area aiming to evaluate the potential and the limitations of the strategy on a real network as well as the integration of variable speed limits and user information strategies. Two different cases of road congestion caused by the presence of on-ramps are studied. Results show that the integration of the two strategies leads to a redistribution of flows, achieving a reduction in the total travel time spent in the network and an increase in the traveled distances, i.e., reducing the overall network time despite the increase in assigned flows. However, an integrated strategy requires adequate transportation supply and mainly crossing demand
Use of gps data for the analysis of vehicular interaction models
No full textThe present paper deals with the study of drivers’ behavior at individual level when
interactions affect vehicle movements in several urban traffic conditions. Main
objectives of the research, which is still on progress, are the investigation of the 2-car
following behavior, even in a non consecutive scheme, through the assessment of
existing well-known models and searching for possible alternative formulations, as well
as the analysis of platoon departures at signals in order to deduce useful information to
improve usual calibration of macroscopic models.
Such an analysis has been performed utilizing data gathered in a series of experiments
involving vehicles equipped with differential high frequency sampling GPS devices and
aiming at studying drivers’ behavior in several urban traffic conditions.
Preliminary promising results obtained for the calibration and validation of car
following models encourage in proceeding along these research directions
A procedure for urban route travel time forecast based on advanced traffic data: Case study of Rome
No full textIn this paper, authors report a procedure to forecast the route travel time, based on different advanced traffic data, both historical and current. The procedure is articulated in two main steps: the first consists in apportioning current route travel time among the links based on historical Floating Car Data; in second step, the obtained link travel times are combined with the current loop detectors data through the measurement data fusion technique; moreover, the Extended Kalman Filter (EKF) correction is applied to a second order traffic model, in order to forecast the link speeds and consequently link and route travel times. Real applications of the proposed procedure concerning both a signalized route of Lungotevere and 6.5 kilometers urban freeway with 14 on/off-ramps in Rome are reported. The results of the forecasted route travel time show a good accuracy until the detected data used to correct the estimation are coherent and the input data, such as flows on ramps, are reliable. The results of the link speeds in terms of RMSE and RME with respect to the data detected by the loop sensors seem to be accurate, however further development will deal with the comparison to the other existing methods. Finally, the results underline, as it is well known, the need of real and reliable data in order to provide a good forecast
Equity measures for the identification of public transport needs
No full textThe present paper deals with the identification of the PT needs taking into account not only effectiveness and efficiency of the PT services but also equity issues. The PT needs refer to the identification of the possible spatial development of corridors, connecting areas of the urban agglomeration, in which there is the need of upgrading the overall performance of the PT services. The main novelties of the paper concern with the determination of the zones with a low “quality” of PT supply and the assessment of priorities and areas of upgrading of the PT system, so supporting the transport planning decisions. This paper focuses on measuring the equity in terms of “quality” of PT system using a new approach based on the computation of the GINI index and the Lorenz curve. In this context, the equity is related with the fair allocation of transport resources. The procedure proposed has been applied in a real-size context of the city of Rome. The case study shows promising results about the robustness of the proposed approach from the methodological point of view and the capability to assess effective measures in a real context. The results of the validation phase of the methodology and the results of the different phases of zone classification underline the strength of the choices made to represent the quality of public transport services and the GINI index approach. Specifically, taking into account the results by the point of view of equity, the GINI index shows a changes of about 7%, that is a promising result considering the few zones selected for the identification of public transport needs
Assessing the impact of Autonomous Vehicles on urban noise pollution
No full textThis paper presents the results of a noise emission study of Autonomous Vehicles (AVs) and their impact on the road network. By comparing the current situation with a future hypothetical scenario (100% AVs penetration), this study highlights the positive effect, in terms of noise pollution, of the adoption of AVs on a real road network (city of Rome). For this scope, a traffic simulation-based approach was used to investigate the effects of AVs on the network congestion. Results show that the full AVs penetration scenario leads to an improvement in the network performances in terms of travel time and average network speed. Moreover, the amount of Vehicle Kilometre Travelled (VKT) shows an 8% increase on longer extra-urban routes, due to the higher capacity impact of AVs on highways, with a consequent load reduction for intra-urban shortcutting routes. These results are also reflected in terms of noise emission. In fact, the central area would benefit from lower noise emission, whereas an increase in traffic volume and speed lead to worsened conditions for some specific highway links of the network. Overall, it was shown that a 100% AVs fleet would have a beneficial effect for the noise pollution, leading to a general reduction of noise emissions, which is more pronounced for intra-urban roads
The value of en-route information on the accessibility to concurrent transit system services
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