1,720,993 research outputs found
Analisi preventiva e monitoraggio della sicurezza in contesti di mutato assetto infrastrutturale. Un caso studio
No full textContributo alla definizione di linee guida per l’analisi di convenienza degli investimenti e la classificazione dei progetti in ordine di priorità
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Smart transportation as a driver of transition: Big data management, behavioral change and the shift to automated vehicles
No full textBackground: Smart mobility can contribute to the design of “Smart cities” to answer users’ requests in terms of transport network efficiency, environmental and social sustainability. Focusing on urban smart mobility issues, the most important aspects are the presence of a connected transportation system, the availability of its information in the arrangement of digital data and the possibility to rapidly communicate it in an effective way to the citizens, urban transportation stakeholders andlocal authorities. Therefore, the challenges for the new era of mobility behavior would range from the effort of big data management and the need to shape the innovation of traveler demand to the changes in requirements for road design. Nevertheless, road safety issues and network working operations must consider all the automated vehicles (AV) as part of an intelligent transportation system. There are types of active safety systems that can influence people’s lifestyles. Aims: This chapter highlights the working mechanism, advantages and disadvantages of ICT technology applied to transportation in the field of safety improvement, environmental sustainability, road redesign and traveler behavioral change. These topics become significant for the study of the key elements associated to the issues with automated vehicles, when “Smart cities” will have new urban settings or mixed traffic. Discussion: This paper leads to redefining the mobility paradigm. Moreover, thanks to the innovation by traffic flow facilities and road equipment, it has been possible to conduct some case studies describing driver behavior towards land-use environment, unfamiliar routes and sharing mobility. Conclusion: The current technology applied to the transportation system already represents the outlook of a new kind of mobility. Many features deal with technical details and others face ethic or legal restrictions. A review of the entire transportation network program should be considered by 2020, worldwide, to make the necessary effort to reach a realistic smart mobility
Exploring Effects of Area-Wide Traffic Calming Measures on Urban Road Sustainable Safety
No full textTraffic calming schemes refer to a combination of road network planning and engineering measures to minimize
undesirable effects of traffic in residential areas. The traffic calming role in urban road network management is,
indeed, to enhance road safety as well as other aspects of liveability for the citizens; in this context accident
reduction can be a realistic objective. Several studies highlight that traffic calming treatments can significantly
reduce road accidents in urban areas. Nevertheless, the increase of the accident rate per kilometre travelled has
been found in urban areas as result of the so-called accident migration phenomenon. Starting from these
considerations, the paper discusses the effects of traffic calming measures on road safety. The paper also aims to
provide a concise overview of knowledge on the potential of the meta-analysis method in detecting the true
effect of traffic calming measures on road safety. Therefore, the role of the road network planning and the
characteristics of urban road network that have to be consistent to the traffic calming objectives are examined.
Finally, authors suggest a methodological procedure for implementing a traffic calming zone in residential areas,
from planning level to road design
Estimating pollutant emissions based on speed profiles at urban roundabouts: A pilot study
No full textThe paper describes the pilot study conducted to assess the feasibility of the empirical approach utilizing vehicle trajectory data from a smartphone app and the Vehicle-Specific Power methodology to estimate pollutant emissions at urban roundabouts. The goal of this research phase is to acquire instantaneous speed data from a sample of six roundabouts located in the road network of the City of Palermo, Italy, and quantify emissions generated by the test vehicle through the examined roundabouts. For the case studies of roundabouts acceleration events in the circulating and exiting areas contributed to about 25% of the emissions for a given speed profile. More in general, the results from this research shed lights for further opportunities to examine infrastructural scenarios when decision makers require to assess changes in the design or operation of urban transportation systems
A Methodological Framework to Assess Road Infrastructure Safety and Performance Efficiency in the Transition toward Cooperative Driving
Full text linkThere is increasing interest in connected and automated vehicles (CAVs), since their implementation will transform the nature of transportation and promote social and economic change. Transition toward cooperative driving still requires the understanding of some key questions to assess the performances of CAVs and human-driven vehicles on roundabouts and to properly balance road safety and traffic efficiency requirements. In this view, this paper proposes a simulation-based methodological framework aiming to assess the presence of increasing proportions of CAVs on roundabouts operating at a high-capacity utilization level. A roundabout was identified in Palermo City, Italy, and built in Aimsun (version 20) to describe the stepwise methodology. The CAV-based curves of capacity by entry mechanism were developed and then used as target capacities. To calibrate the model parameters, the capacity curves were compared with the capacity data simulated by Aimsun. The impact on the safety and performance efficiency of a lane dedicated to CAVs was also examined using surrogate measures of safety. The paper ends with highlighting a general improvement with CAVs on roundabouts, and with providing some insights to assess the advantages of the automated and connected driving technologies in transitioning to smarter mobilit
Researching a Capacity Model for Multilane Roundabouts with Negotiation of the Right-of-Way between Antagonist Traffic Flows.
No full textThis article summarizes a research program designed to assess operating conditions through capacity estimation
at not-conventional roundabouts characterized by a central island with a large diameter and by two (or more)
entering and circulating lanes. Although giving priority to vehicles on circulatory roadway is the nominal
operating rule, on-field observations highlighted that in some infrastructural schemes of the type considered in
this research drivers negotiate the right-of-way according to a consensus pattern that alternates between
antagonist traffic flows, similarly to that observed at all-way-stop-controlled intersections. Considering the
peculiarity of the way of working at roundabout schemes being examined, as well as difficulties faced in the
application of models based on gap-acceptance theory to evaluate performances, an analytical capacity model
derived from field observations was proposed for multilane not conventional roundabouts.
Drawing inspiration from the iterative procedure proposed for capacity estimates at all-way-stop-controlled
intersections, a calculation algorithm organized in 5 subsequent computational steps was developed in order to
evaluate capacity at each entering/circulating lane for the type of roundabouts examined in this research. Results
compared to those calculated by models for modern roundabouts show the effect on estimates of capacity raised
by a more realistic operating pattern and indicate that the capacity model may be able to estimate parameters
useful for planning and design purpose
Estimating traffic operations at multi-lane roundabouts: a case study
Full text linkThis paper addresses traffic modeling issues at urban multi-lane roundabouts where, despite circulating vehicles have priority, negotiation of the right-of-way can occur between antagonist traffic flows, as a result of minor drivers’ failing to obey the nominal operating rule (stop or yield control). Existing models for the estimation of operational performances have the shortcoming of not representing the interdependencies between entering and circulating vehicles at multi-lane roundabouts. An analytical capacity model derived from field observations was developed for this kind of intersections in a previous study. The complexity of the model lies in the difficulty of observing the behavioral parameters which are needed to implement the model. A procedure to get unknown behavioral parameters from traffic surveys is here proposed. This concerns saturation headways, often eluding direct observations due to rare occurrences of traffic conditions in which they can be observed. The unknown parameters were estimated through a regression model using on field
data collected at a multi-lane roundabout. The presence of data correlation within a cluster of observations required the estimation of the regression parameters through a generalized estimating equation model. Results gave insight into the analysis of operations at multi-lane roundabouts, containing evidence to support assumptions made for the estimation of unobservable parameters
Emission factors related to vehicle modal activity
No full textPolluting emissions depend on vehicle characteristics and on traffi c conditions expected after the construction
of a road project. Nevertheless, in the assessment of new projects, the task of road designer becomes uncertain when the reduction in polluting emissions has to be evaluated. Moreover, vehicle emissions are highly linked to modal vehicle activity, but current emission rate models do not properly predict on-road vehicle emissions produced by modal traffi c events, as those occurring at intersections.
Modal emission models require the analysis of modal activity at a microscale level in order to evaluate emission factors by a single mode (idle, acceleration, deceleration, and cruise). This evaluation can be standardised with reference to the type of road, volume-to-capacity ratio and fl eet composition. On the contrary, the mesoscopic level for vehicle modal activities, as it is usual in traffi c analysis, will result appropriate to reach correct emission estimates.
In order to explain factors affecting polluting emissions, a research programme targeted to the development
of a methodology to be applied to traffi c studies has been undertaken. This paper reports the results of
an exploratory analysis, based on examples of driving patterns, with the specifi c purpose to measure and to
interpret vehicular polluting emissions in road situations different for geometric and traffi c conditions. Results
referred to in this paper show that, for a specifi c traffi c condition, estimates of vehicle polluting emissions can
be obtained from emission factors proper to each elementary modal activity and from proportion of time spent
by vehicles in each modal activity as defi ned at mesoscopic leve
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