Turbo roundabouts: geometric design parameters and performance analysis

A turbo roundabout is a particular type of roundabout where entering and circulating lanes are bounded by traffic signs and by non-mountable curbs. The physical separation between lanes, both at entries and on the ring, helps to prevent side collisions crossing the roundabout.The main advantages of turbo roundabouts are: i) reduction in the number of potential conflict points; ii) lower speed of vehicles passing through the intersection; iii) safety conditions at the intersection due to lower risk of side-by-side accidents. Also, in some cases the capacities of turbo roundabouts are higher than the capacities of conventional roundabouts.This paper presents an estimation of capacity, delays and level of service of turbo roundabouts in undersaturation conditions, considering both vehicular flow and pedestrian stream. It also examines the geometric parameters of the central island and circulating lanes in several turbo roundabout layouts

Image analysis for detecting the transverse profile of worn-out rails

Over its useful life a railway track is subject tomany mechanical and environmental stresses which graduallylead to its deterioration. Monitoring the wear condition of therailway superstructure is one of the key points to guarantee anadequate safety level of the railway transport system; in thisfield, the use of high-efficiency laser techniques has becomeconsolidated and implemented in diagnostic trains (e.g. the“Archimede train” and the “Talete train” ) which allow to detectthe track geometric parameters (gauge, alignment, longitudinallevel, cross level, superelevation defect, etc.) and the state of railwear (vertical, horizontal, 45-degree etc.) with very highaccuracy. The objective of this paper is to describe a new nonconventionalprocedure for detecting the transverse profile ofworn-out rails by means of image-processing technique. Thismethodological approach is based on the analysis of theinformation contained in high-resolution photographic images ofrails and on specific algorithms which allow to obtain the exactgeometric profile and the measurement of the relevant deviationscompared to new rails of the same typology.The analyses and the first results, obtained from laboratoryresearches, concern rails cross sections taken from railway linesunder upgrading. The procedure has shown high precision in thewear evaluation as well as great rapidity in being performed

un approccio teorico-sperimentale per la ricostruzione del profilo trasversale di rotaie usurate

La sovrastruttura ferroviaria durante la sua vita utile è sottoposta oltre ai carichi dinamici generati dai rotabili (azioni verticali, laterali, ecc.), anche ai carichi termici e ad azioni ambientali di varia natura. Tali sollecitazioni, interagendo sinergicamente tra loro, determinano il deterioramento della sovrastruttura ferroviaria inteso come discostamento dalla configurazione geometrica di progetto e l’usura dei singoli componenti del binario e della massicciata. Per valutare lo stato di efficienza della sovrastruttura è consuetudine far riferimento ad alcuni parametri geometrici del binario che, peraltro, permettono di formulare un giudizio oggettivo circa il livello di sicurezza offerto dalla linea ferroviaria in una data tratta. A tal riguardo, in genere, vengono esaminati distintamente in seguenti parametri geometrici [1] e [2]: i) scartamento; ii) allineamento “A”; iii) livello longitudinale “L”; iv) livello trasversale XL; v) scarto di livello trasversale SCARTXL; vi) difetto di sopraelevazione H; vii) sghembo; viii) ulteriori parametri geometrici (scartamento depurato ed in media mobile, allineamento su base 20 m, ecc.). Invece, per quanto riguarda il deterioramento dei materiali, generalmente vengono presi in esame: i) usura verticale della rotaia; ii) usura a 45° della rotaia; iii) usura orizzontale della rotaia; iv) presenza nelle campate delle rotaie di fori, fenditure, e stato delle saldature alluminotermiche ed a scintillio nelle lunghe rotaie saldate; v) tenuta degli attacchi; vi) stato delle traverse in c.a.p. ed in legno. Con riferimento allo stato di usura delle rotaie, oltre ai tradizionali metodi di auscultazione, in futuro, in ambito ferroviario, potrebbero trovare ampio impiego anche le tecniche basate sull’image processing, in grado di ricostruire con alto livello di dettaglio il profilo trasversale di una rotaia in esercizio, e dunque, di poter effettuare il confronto con il profilo originario (rotaia nuova) al fine di determinare lo stato di usura del profilato. Tale approccio metodologico, dettagliatamente descritto nei seguenti paragrafi, si basa sulle “informazioni” contenute in immagini fotografiche ad alta risoluzione delle rotaie e su specifici algoritmi che permettono di ottenere l’esatto profilo geometrico delle rotaie stesse.A new procedure for reconstructing the transverse profile of worn-out tracks by means of the image-processing technique is studied. In order to analyze the image of a track plane section, the first step of the procedure is the edge detection of the transverse profile through Canny's algorithm. This algorithm examines the behavior of the gradient operator applied to a noisy contour. Moreover, the algorithm is able to distinguish some clearer pixels near the track edge which do not belong to its micro-wrinkles, obtained from an enlargement of the upper profile of the railhead. For every chromatic plane of the analyzed image, a median filter is applied. The centroid position of the worn-out track and its contour coordinates were determined, gathered from Freeman's algorithm developed on the result formalized by relations after carrying out the proper morphological closing operations. The distances between the two profiles have been determined by the intercepts of the straight lines from the centroid of the profile I

Piezoelectric energy harvesting from raised crosswalk devices

This paper presents the main characteristics of an experimental energy harvesting device that can be used to recover energy from the vehicular and pedestrian traffic. The use of a piezoelectric bender devices leads to a innovative approach to Henergy Harvesting. The study focuses on the definition and specification of a mechanical configuration able to transfer the vibration from the main box to the piezoelectric transducer. The piezoelectric devices tested is the commonly used monolithic piezoceramic material lead-zirconate-titanate (PZT). The experimental results estimate the efficiency of this device tested and identify the feasibility of their use in real world applications. The results presented in this paper show the potential of piezoelectric materials for use in power harvesting applications

Ballasted track superstructures: performances of innovative railway sleepers

A railway sleeper is the structural element which transversally connects the two rails by means of fastening components, thus ensuring its gauge. Its additional function is to firmly secure the track to the ballast and to distribute the loads transferred from railway carriages to the ballast. One of the most important parameters in the characterization of performance given by railway sleepers is represented by their lateral resistance to the sliding: the higher its value increases, the better the track stability becomes, thus reducing the frequency of maintenance interventions necessary to keep the superstructure efficient. This article focuses on the performance of two innovative railway sleepers, recently patented in Italy and called the “EGA” and “HP-BB”, under different efficiency conditions of the ballast. The research is carried out through a comparative assessment of traditional mono- and bi-block sleepers, evaluating the resistance of the single sleeper thought as independent of the other constituents of the trac

Turbo-Roundabouts: a Model to Evaluate Capacity, Delays, Queues and Level of Service

A turbo roundabout is a particular type of roundabout where entering and circulating lanes are bounded by traffic signs and by non-mountable curbs. The physical separation between lanes, both at entries and on the ring, helps to prevent side collisions crossing the roundabout. The main advantages of turbo roundabouts are: i) reduction in the number of potential conflict points; ii) lower speed of vehicles passing through the intersection; iii) safety conditions at the intersection due to lower risk of side-by-side accidents. These aspects make turbo-roundabouts more appropriate than roundabouts when a higher level of safety has to be guaranteed, particularly in presence of relevant pedestrian and two-wheels traffic volumes. Also, in some cases the capacities of turbo roundabouts are higher than the capacities of conventional roundabouts. This paper presents an estimation of capacity, delays, queues and level of service of turbo roundabouts in undersaturation traffic conditions, considering both vehicular flow and pedestrian stream. It also examines the geometric parameters in several turbo roundabout layouts and presents one case study from real world concerning the conversion of existing large diameter roundabout into two linked turbo roundabouts

Turbo roundabouts:geometric design parameters and performance analysis

A turbo roundabout is a particular type of roundabout where entering and circulating lanes are bounded by traffic signs and by non-mountable curbs. The physical separation between lanes, both at entries and on the ring, helps to prevent side collisions crossing the roundabout. The main advantages of turbo roundabouts are: i) reduction in the number of potential conflict points; ii) lower speed of vehicles passing through the intersection; iii) safety conditions at the intersection due to lower risk of side-by-side accidents. Also, in some cases the capacities of turbo roundabouts are higher than the capacities of conventional roundabouts. This paper presents an estimation of capacity, delays and level of service of turbo roundabouts in undersaturation conditions, considering both vehicular flow and pedestrian stream. It also examines the geometric parameters of the central island and circulating lanes in several turbo roundabout layouts