Abstract:The functional performances of conventional roundabouts (single-lane and multi-lane) and innovative roundabouts (spiral, flower, C and turbo) can be improved through right-turn bypass lanes controlled by stop, yield or free-flow signs. The article presents evaluations of the emissions of air pollutants (carbon dioxide, nitrogen oxides, particle pollution (PM10 and PM2.5)), fuel consumption and construction, management, energetic and environmental costs in roundabouts without or with bypass lanes (controlled by stop, yield or free-flow). The suggested methodology has a general character and can be applied as a multi-parametric criterion for choosing road intersections, although, in the present paper, it has been employed only for a case study. For the aims of this research, we employed recent closed-form formulations to determine roundabout performances; moreover, we used the COPERT IV ® software to estimate air emissions in nine different types of vehicles. Numerous traffic simulations were carried out. The variation in the maximum hourly traffic Qmax and annual traffic QTOT provided the appropriate domains of the examined geometric layouts, both in functional and environmental terms and with regard to generalized costs, estimated for a 10-year period. It resulted that the introduction of right-turn bypasses in all arms of conventional roundabouts with a one ring lane and one lane at the entries (single-lane roundabouts) is the most cost-effective when the flows entering the roundabout are higher than Qmax = 2000 veh/h. Moreover, free-flow bypass lanes always OPEN ACCESSSustainability 2015, 7 5839 provide greater capacity and lower delays than stop-or yield-signaled bypasses. However, with extremely high Qmax values, stop-controlled bypasses guarantee lower fuel consumption, while those with a yield sign lower total costs.

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Abstract:A simplified version of the ecological footprint method is proposed for assessing the environmental performances of urban transportation systems. The method, starting from the knowledge of the composition of the running vehicular fleet, is here applied to a southern Italian province. It represents a synthetic indicator of the environmental pressure exerted by the system also matching the pollutant emissions with the carrying capacity of the site. Particularly, the forested area needed to absorb the CO2 emissions of the system is compared with the total forested area of the province. The results of the case-study indicates the yearly maximum distance that each vehicle of the fleet can cover in order for their emissions to be absorbed by the surrounding forested area. Specifically, if all cars of the fleet would travel for 10,000 km/year, 97% of the forested area would be involved. Thanks to its features, this indicator can be usefully adopted for ranking different transportation options. Therefore, it could allow local administrations to environmentally hierarchize alternative plans concerning urban transportation choices.

The work arises from the consideration that the environmental impact of a road cannot be limited to the analysis of its constituent materials, even if correctly analyzed in their life cycle. In fact, a given road not only consists of the pavement and subgrade, but also includes several different components and accessories (e.g., road marking, drainages, safety barriers, etc.) that contribute to set a road infrastructure in operative condition. As a matter of fact, only limited attention has been paid in the scientific literature to roadside components, unlike pavement and traffic flow. In the present work, the environmental burden of one of these components, i.e., the safety barrier has been investigated using the LCA methodology and critically compared with that exerted by pavement and traffic flow, in order to establish their relative contributions. To accomplish this task, an application referring to a segment of a typical Italian highway is proposed. This case study seems to confirm that the environmental burden of the guardrail cannot be neglected, because it is often even numerically comparable with that of the pavements. This paper concludes that, in order to obtain a more comprehensive environmental evaluation, this type of analysis should be extended to this component and also to all of the other components and activities that make a road transportation system ready to be used. Such an integrated approach may be useful for administrations to better comply with the current sustainability standards and guidelines.

The theme of safety for vulnerable road users (disabled, elderly, and children) in urban areas plays a role of primary interest for many implications in quality of life. The deficiency of safety on city streets is primarily due to the simultaneous presence of different components of traffic in an increasingly complex and inappropriate ambient for their cohabitation. In urban areas the road intersections, which are crossed by different categories of traffic (motorized vehicles, pedestrians, non-motorized vehicles), represent a critical node, both in terms of quality of circulation that of road safety. In recent years there has been the 76.62% of accidents in the urban area, with the 13% of accidents involving pedestrians of which about 30% of accidents occurred near intersections. All these reasons explain the complexity in the planning of an intersection, particularly when vulnerable users are involved. In this paper we propose an applicative study of "pedestrian crossings", regulated by traffic lights or free, and what factors affect their planning and design to achieve an optimal quality of service and high safety standards. The study area involves one of the main streets of city of Palermo, which link the city center and some of the suburbs, focusing on the design of pedestrian crossings and their location in the urban context, starting by existing legislation in order to achieve an optimization of the number of pedestrian crossings, the distance between them and traffic light cycle if present. In particular we can design a possible new layout of pedestrian crossings, starting by analysis the current configuration and its critical points and simulating different future scenarios that take into account the dual role of the street inside and outside the district and in the whole urban network.

This chapter presents the social innovation project “TrafficO2”, a support system for decision-making in the field of transportation that tries to push commuters towards more sustainable mobility by providing concrete incentives for each responsible choice. After focusing on Palermo, Italy, the context of this case study, this chapter provides a detailed description of the TrafficO2 model. Specifically, the chapter deals with the analysis of a selected sample of users among Palermo University students who commute daily to their respective University departments on campus. Starting from the modal split of the actual situation (Status Quo scenario), another behavior scenario (Do your right mix) is designed and promoted to encourage users to create a better mix of existing mobility means and reduce the use of private vehicles powered by combustibles. The first test that was performed confirmed the reliability of the initiative.