1,720,973 research outputs found
Fixed point models for the estimation of O/D matrices using traffic counts on congested networks
No full textConnectivity carbon and noise levels in the airport neighbourhood
No full textMany airport connectivity measures have been studied and proposed in the literature to capture both the effects of increased/reduced airport connectivity and the quality level of the connections. This study focuses on the relationship between connectivity – measured by air links and number of flights – and airport carbon/noise local levels. Although airport connectivity evokes the perception of geographical distances covered by air services, on ground connectivity consequences affect directly airport neighbourhood. Increased airport connectivity generally generates increasing number of airport movements that, in turn, produce higher levels of environmental externalities, such as noise and carbon emissions, mainly on local communities. To quantify such relationship, the Viable Connectivity Index (VCI)is proposed, which combines connectivity and noise/carbon levels at the airport. The index could be used as a preliminary test of airport operator policy actions to identify suitable policies addressed to reduce their noise and carbon amount and keep at the same time good connectivity levels. The test case of Bologna airport - a large regional airport in Northern Italy - is also discussed
Impacts of connected autonomous vehicle platoon breakdown on highway
No full textConnected Autonomous Vehicles (CAVs) are seen as an opportunity to improve traffic efficiency and safety. However, further studies are needed to prove such positive effects. Particularly, there is a lack of quantitative research on the impacts of CAV breakdown in mixed traffic flow conditions (i.e., CAVs and Human Driven Vehicles, HDVs). The aim of this research is to explore the impacts generated by the breakdown of the leading vehicle of a CAV platoon in mixed traffic conditions, which in turn generates CAV platoon breakdown (i.e., platoon dispersion), by considering several CAV market penetration rates (MPRs) and platoon size. In this perspective, a control algorithm (“avoidance algorithm”) for modelling CAVs and HDVs behaviour to avoid obstacles (i.e., breakdown CAV platoon) has been developed and tested on some simulation scenarios in order to derive key traffic flow parameters. The dynamic characteristics of traffic flow with CAV platoon breakdown have been explored for both low and high traffic flow volumes. Finally, potential conflicts, congestions, as well as energy consumption and CO2 emissions resulting from the breakdown of CAV platoons in mixed traffic streams have been assessed and discussed. Results suggest that (1) CAV platoon breakdown can reduce the traffic capacity by about 20 %; (2) higher CAV MPRs are more suitable for enhancing highway safety even in breakdown conditions, decreasing energy consumption, and reducing CO2 emissions; (3) platoon size should be limited to 4, since larger sizes affect traffic safety, increases vehicle average delay time as well as energy consumption. The obtained results provide useful insights for transportation planners and transport infrastructure management companies to design and apply policies aimed at improving driving conditions, traffic quality, and safety on highways
Green airport investments to mitigate externalities: Procedural and technological strategies
No full textTransport systems are important pollution sources, mainly in terms of greenhouse gases, noise and land consumption. To mitigate the problem and safeguard airport development at the same time, the involved stakeholders are fixing goals, priorities and duties in order to promote the sustainable development of the air transport industry at global level and the wellness of local communities as well. It is desirable to estimate airport noise and carbon impacts in order to suitably manage them and identify strategies in line with the concept of green economy. In this chapter, a general framework to identify optimal procedures and methods to evaluate the effectiveness of policies addressed to reduce airport impacts on the airport surroundings is proposed. The case study of the airport of Bologna is presented as an example of Transport Company that effectively operates to minimize its noise and carbon impacts. According to the proposed general framework, impacts and estimated costs to achieve the status of green company have been computed
A modelling framework to support the development of last-mile urban freight distribution systems based on the use of cargo bikes
Full text linkNowadays there is a growing interest in cargo bikes to mitigate the detrimental effects of urban freight transport, since the last-mile segment of freight delivery process is being challenged to reduce the number of vehicles, the distance travelled and the environmental impacts. This paper presents a modelling framework that, starting from the key reference units (freight demand, deliveries, and vehicles) and defining the relationship among stakeholders and choice dimensions, can support the implementation of freight distribution systems based on cargo bikes. In detail, the work follows a general approach and is focused on the estimation of the share of demand that can be satisfied by cargo bikes, freight flows in terms of number of deliveries and trips, obtained by assigning freight demand to the transport network. The model has been applied to the test case of the city of Ravenna by implementing several scenarios
Environmental and Operational Efficiency of Integrated Urban Last-Mile Freight Distribution Systems Based on the Use of Cargo Bikes
No full textDoes the information provider choose to promote public transport use or protect public health? A case study in China
No full textBackground: Health risks from air pollution require cutting motorized private vehicle use. Providing new public travel patterns, along with appropriate smartphone-based multimodal travel information services (SMTIS) is considered an effective way to alleviate this stress. However, air pollution is not likely to be solved overnight. There is a growing demand for more detailed air pollution information accessible through mobile apps to avoid exposure to pollution,
which may increase the use of private cars. So far, little is known about this contradictory behavior.
Methods: Based on 1926 observations obtained from a stated preference experiment conducted in Shanghai, a mixed logit model was developed to investigate the effect of SMTIS on travelers’
mode choice behavior. Specifically, this study aims to reveal the impact of progressively providing typical multimodal information, social influence information, and air pollution information expressed in cigarette equivalents on commuters’ choice of travel modes, including private car, park-and-ride (P&R), and customized bus.
Results: Information offered by SMTIS, including travel time, travel cost, available parking spaces, comfort level, and air pollution information, exerts significant influences on travel mode choice.
Also, there is observed taste heterogeneity for such information across the population. Respondents placed less emphasis on air pollution information during commute trips than on travel time. Providing information on modal pollution exposure prevents people from using public transport. Even when air quality is good, we still observe an increase in the proportion of people choosing cars. With regard to social influence information, people were more likely to choose P&R when online word-of-mouth about P&R displayed a positive propensity, while the percentage of other travelers who had selected P&R did not exhibit a significant effect.
Implications: The findings provide valuable implications for the design of low-carbon traffic management policies and the deployment of multimodal information services
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
