Case studies of landscape and environmental impact evaluation of roundabouts

This paper is a follow-up to a previous one that presented a new method for evaluating the landscape and environmental impact of roundabouts borrowed from building technology and based on the needs, requirements and performance expected from an object rather than on prescriptions for and descriptions of its dimensions and quality. The proposed method aims at defining criteria to set up an information structure based on a need and performance approach capable of evaluating impacts on the landscape and environmental integration. After a brief résumé of the above-mentioned principles, two applications are presented in order to highlight two practical developments. The roundabouts on which the applications are focused are located in an urban and in a rural environment respectively in the Northern part of Italy. Obviously their analysis cannot be considered comprehensive of all possible cases but it covers a large proportion of them. Differences between the two roundabouts are many and they concern, besides the landscape and environment, geometrical dimensions, type of flow, presence of weekday users (pedestrians and bikers). The final evaluation sheets are presented and through them it is relatively easy to single out the problems and drawbacks of the roundabouts from the landscape point of view

Landscape and Environmental Impact Evaluation of Roundabouts

The interest of researchers and practitioners on roundabout solutions has been growing increasingly in the last decades. The often large areas occupied by this type of intersections require special attention on the use of ground and the preservation of the natural, environmental and architectural heritage. This aim also presents the opportunity for evaluating their impact on the landscape and environment. The paper proposes a new method developed for roundabout evaluation (but generalizable to other infrastructures and fields) borrowed from building technology and based on the needs, requirements and performance expected from an object rather than on prescriptions for and descriptions of its dimensions and quality. Applications on two roundabouts are presented in order to highlight practical developments. Their final evaluation sheets are presented and through them it is relatively easy to single out the problems and drawbacks of the roundabouts from the landscape point of view

Effects of a tradable credits scheme on mobility management: a household utility based approach incorporating travel money and travel time budgets

We investigate the influence of a new mobility management measure, the tradable credits scheme (TCS), on the daily travel mode choices of individuals. Generally, we assume the individuals’ travel consists of different modes, e.g. private car mode and mass transit mode. In order to control the rapid increase in use of the private car mode in an area, policy makers may wish to implement a TCS basing on the vehicle kilometre travelled (VKT). The effects of the TCS are investigated in this paper based on a utility-theory travel demand model proposed by Golob et al. (1981), a household utility based model incorporating proposed travel money and travel time budgets. The empirical investigation is based on comparison studies of the short-term response and long-term effects with and without TCS. It finds that the implementation of TCS has not a clear impact to the value of time of household in the short-term, and the presence of TCS does not affect the linear relationship between travel time budget and travel money budget over long term. Numerical results demonstrate that the TCS will affect the travel distance of the available transport modes differentially, according to different levels of annual household income

CONTROLLO DI UN DEFLUSSO AUTOSTRADALE CON RETI NEURALI

TESI DI DOTTORATO IN INGEGNERIA DEI TRASPORT

The analysis of roundabouts through visibility

Visibility is one of the most important issues in almost all geometrical norms for road and intersection design. This paper deals with the question of visibility on roundabouts but from a different point of view in respect of the norms that have currently been adopted regarding capacity and safety issues. Attention is focussed on the simple consideration that many trajectories, in well designed roundabouts, are curvilinear and therefore two possible measures of distances between vehicles can be calculated along their trajectories and directly (such as the Euclidean distance) between the vehicles themselves. The first measure is associated with the distance in terms of the conflict point and the second one represents the sight distance between the vehicles. These two distances are generally different on a roundabout. The aim of the paper is to demonstrate both analytically (through a mathematical representation) and experimentally (by using trajectories processed from video images shot on a working roundabout) that in many cases the visual distance is less than the distance to the conflict point. This difference changes in time (and space) according to the speeds of vehicles. Comparisons between the two approaches, applied to a real case, are also provided. Three cases are taken into consideration (1- two vehicles both circulating both in the circulating roadway, 2-one is circulating in the circulating roadway and the other is entering, 3-both vehicles are entering) highlighting the effect that visibility can produce

A topological analysis of underground network performance under disruptive events

Every disruptive event in a transportation network has costly consequences both for users and for managing companies. To prevent large declines in the desired level of mobility, it is important to locate the most important nodes of the network, and to strengthen them. In this paper, we focus on underground networks. We introduce a methodology based on graph theory to locate the most important nodes, and we apply it to Washington D.C. network as a case study, and to the underground networks of 34 cities all over the world

Novel centrality measures and applications to underground networks

Two novel centrality indices, PathRank and Icentr, are defined. PathRank is a generalization of the PageRank algorithm, suitable to rank nodes of undirected graphs according to number and weight of paths in the graph. Icentr ranks the nodes of the graph by means of a combination of the weights of nodes and edges, scaled according to the distance from each node, one at a time. We apply the two novel indices to underground transportation networks, since these networks represent an infrastructural backbone for the transportation system of most big cities over the world. The characterization of the most important components of those networks and the simulation of their responses when they stop working properly, are vital for maintaining the mobility service at a desirable level. Since there are different ways to associate a graph to an underground network according to the degree of detail and aims of the study, we describe the methodology we adopted to associate a graph to such a network. The methodology was applied to 34 underground networks of worldwide cities, and the resulting graphs constitute the reference dataset. A detailed study of both Boston network and the dataset is proposed as prototypal for either a graph alone or all graphs in a dataset. Results show how different features of graphs are revealed by the two novel indices