Two-Geometry Roundabouts: Estimation of Capacity

The authors have already developed and studied the Two-Geometry Roundabouts in terms of design principles. This paper in fact is the natural extension of another article named - Two-Geometry Roundabouts: Design Principles - in which the authors discussed the main concepts in the Two-Geometry Roundabouts and the details that determine their success. However, when talking about roundabouts in general, it is also of fundamental importance to talk about the evaluation of their capacity. The Highway Capacity Manual (HCM) provides a rigorous method for estimating the capacity (and assessing the Level of Service) of conventional roundabouts. However, the Two-Geometry Roundabouts are unconventional roundabouts and therefore this paper aims to answer the question: “which model should be used to calculate the capacity of the Two-Geometry Roundabout?”. To do this, the Italian legislation will first be considered and a comparison will be made between it and the HCM methodology. After that, the 2 methods most used to date for calculating the capacity of the Two-Geometry Roundabouts (SETRA method and Brilon-Wu method) will be illustrated. Finally, before drawing conclusions, possible future developments will also be introduced in the context of this research, starting from some simulations made with the Aimsun software on a Two-Geometry Roundabout in Italy

Raised crosswalks and their design features in traffic calming

A road hump, or speed hump, is a traffic calming device used to reduce vehicle speed and volume on residential streets. Road humps are placed across the road to slow traffic and are often installed in a series of several humps in order to prevent cars from speeding before and after the hump. Speed humps are used in locations where very low speeds are desired and reasonable. Speed humps are typically placed on residential roads and are not used on major roads, bus routes, or primary emergency response routes. In Italy, the road humps are often built in shape of raised crosswalks, or RCWs, and they are generally placed both close and between intersections. This paper deals with the analysis of observed data on a large sample of RCWs located in Tuscany, central Italy. Such data were referred both to geometry characteristics of the single raised crosswalk and recorded differences in vehicle speeds before and after it. Speed data were gathered using two automatic radar-recorders for each one of the sampled raised crosswalks. All the collected data were analyzed trough statistical tests in order to assess their homogeneity or not between different locations and various types of roads. Finally, we were able of making some conclusions and highlighting design aspects. On one side, RCWs with similar geometries and higher heights (about 15 cm) have similar effects on vehicle speeds lowering, regardless of local conditions (location, road geometry, driver behaviour, etc.). Moreover, raised crosswalks installed in a series have strong efficacy than the isolated ones. On the opposite side, the effects of raised crosswalks with smaller heights (less than 6 cm) show clearly a very low influence on vehicle speed variations

The integration of buses with a high level of service in the medium cities urban context

In the last decade the world has witnessed a large diffusion of the BHLS (Buses with a High Level of Service) systems. This growth was sparked off by the successful implementation of the first BHLS system in Curitiba (Brazil) in the 1970s, also named bus rapid transit (BRT), which was able to achieve reliable and efficient transport service at reduced costs. The main reason of BHLS’ spread is mostly due to its proper characteristics that allow to combine flexibility and low costs typical of bus based systems with reliability, efficiency, speed, frequency, comfort and safety offered by the more costly LRT (Light Rail Transit).These systems are generally characterized by modern environmentally-friendly vehicles, reserved bus-ways and applications of intelligent transport systems (ITS) based technologies. All these characteristics are very important features of the so-called smart mobility. The aim of this paper is to describe the working process adopted to design a new BHLS line haul in Pisa (Italy) connecting Pisa Central Railway Station with the Hospital of Cisanello. The paper shows how the new BHLS line could be fairly suited to the Italian context, and in particular to a medium sized city like Pisa, characterized by narrow streets, high density of building and need of sharing large part of bus paths inmixed traffic. Furthermore, this paper evaluates the feasibility of a solution to solve the problem concerning the give-bus priority.Signalized roundabouts with controlledtraffic light and giving priority to BHLS vehicles, that allow buses to cross the intersection without stopping delays, have been proposed. The results of such design analysis on one side confirm line haul feasibility, and on the other side show that the expected level of service of the proposed design solutions is fairly good. Finally, some brief considerations are also drawn on BHLS transit general features giving design insights in respect to a mid-size urban area requirements

Illegal pedestrian crossing at a traffic light: a study on tourist behaviour

Illegal pedestrian crossing situations at signalized intersections are observed worldwide. The main goal of this study was to observe attributes and determine the proportion and type of pedestrian violations and dangerous crossing situations at a traffic light located in a recreational tourist urban environment, i.e. the beach town of Viareggio on the coast of Tuscany, Italy. A large signalized intersection placed close to the beach was observed for some days in Summer 2015, for several hours, both in the morning and in the afternoon, to collect data. The main aim was to identify the illegal pedestrian crossing behaviour with red traffic light. Pedestrian crossing data were recorded with a video camera. Then, the video data were processed using a semi-automated software self-written in MATLAB to extract information on different pedestrian factors. Some factors, identified in the current literature as having an influence on the proportion of violations, such as age, sex and group size, were analysed. Furthermore, the impact of the amber length time on the proportion of dangerous performed crossings was studied. The obtained results highlight that pedestrians in a recreational tourist environment are generally more in compliance with traffic light than those in a weekday urban context. It is also important to pay particular attention to pedestrian yellow time (amber steady man) in order to avoid dangerous legal crossings. In fact it was often observed that pedestrians start to cross on the green walking man but end under the red light

Modeling and calibrating capacity of large roundabouts

Roundabout models, available in the literature widely, vary between one method and another. Majority of the models are solely based on circulating fl ow to estimate capacity. The relationship between maximum entry fl ow of large dual and triple lane roundabouts and their geometric and traffi c characteristics is investigated here for saturated fl ow condition using multivariate analysis. The developed model, based on the data gathered from 13 roundabouts in Bahrain, matched the fi eld data reasonably well. The signifi cant predictors, out of 60 tested ones, included circulating and exiting fl ows, number of entry and circulating lanes, circulating and entry widths, inscribed diameter and fl are length. Capacities predicted through various international models varied considerably with both the developed model and the fi eld data. The international models were then calibrated against the model, and consequently the fi eld data, so as to have signifi cant match with the two. The procedure followed in developing the model and calibrating the international models consisted of eight stages. It involved identifi cation of signifi cant correlation of individual predictor with capacity, multivariate regression analysis, model smoothing, multi-collinearity test, redevelopment of the model after adjusting the variables causing collinearity, comparison analysis with seven known international models and calibration of the international model. While UK, aaSIDRA and French models required around 50% reduction to match the developed model and actual data; US FHWA and Swiss models required 25% reduction and US HCM and German models required just 8% adjustments. Such clear variations call for further research. The fi ndings assist the urban planners as when to shift from one type of intersection control into another involving roundabout, and vice versa

Improvement of the West road corridor for accessing the new hospital of Lucca (Italy)

This paper deals with the study of a road corridor in the historical city of Lucca (Tuscany, Italy) following the transfer of the city hospital to a new location, which took place in May 2014. Lucca is surrounded by a ring road and the road corridor study was related to alleviating the problems actually experienced by ambulances travelling from the urban ring road to the new hospital. The corridor road length is about 1.5 km (i.e. 0.93 miles), and there are seven different intersections along the corridor, spanning from signalized to two-way stop controlled and roundabouts. SIDRA INTERSECTION 6.0 (NETWORK version) was used to analyze the two scenarios; namely, the “present situation” and the “design situation” to verify the effectiveness of some proposed local changes and intersection improvements. The analyses indicated that “Level of Service D” (the target value required in the urban field) could be achieved for the “design situation” while “Level of Service F” was indicated for the “present situation”. The analysis results strongly supported the design proposal of improving the west road corridor for accessing the new hospital of Lucca. This is particularly important considering that ambulances are the most crucial users of the road corridor. The analyses also showed that significant improvements could be made to traffic performance in the road corridor in general, including environmental benefits in terms of reduced fuel consumption and emissions. This study has been possible thanks to SIDRA INTERSECTION 6.0 (NETWORK version) that showed its capability of modelling both single intersections and the road corridor

Two-Geometry Roundabouts: Design Principles

Although concentric multi-lane roundabouts have a higher capacity than single-lane roundabouts, they have the disadvantage of a higher driving speed through the roundabout. They also reintroduce the possibility of lane changing on the roundabout and hence raise the risk of accidents. The authors developed and studied the two-geometry roundabout in an attempt to deal with these and other drawbacks. This type of roundabout has the following features: no lane changing (or at least as little as possible) on the roundabout; lower driving speed through the roundabout; advantages in the manoeuvers of heavy-duty vehicles. This paper discusses the concept of the two-geometry roundabout and the details determining success. In detail: first of all, the characteristics of the single-lane and multi-lane roundabouts will be illustrated, focusing on the problems of the latter; after which the development, the main characteristics and the typologies of the two-geometry roundabout will be illustrated (with some examples attached); finally, we will focus on the positive effects of the two-geometry roundabout on heavy vehicles. In the final part, the methods for calculating the capacity of the two-geometry roundabout will also be introduced, and therefore the conclusions of the paper. The paper discusses the concept of the Two-Geometry Roundabout and outlines its principal advantages. We first develop, the main characteristics and typologies of Two-Geometry Roundabouts illustrated (with some examples attached); therefore, we focus on the positive effects of the Two-Geometry Roundabout with particular attention on heavy vehicles. Finally, we present methods for calculating the capacity of the Two-Geometry Roundabout and conclude the paper

Upgrading Traffic Circles to Modern Roundabouts to Improve Safety and Efficiency – Case Studies from Italy

This paper presents a procedure for analysing safety and operational improvements made possible by converting traffic circles to modern roundabouts. An Italian case study is presented for alternative layouts under various traffic demand scenarios. In the application of the procedure, the average waiting times and queue lengths at entries are computed with an analytical capacity model, using default values for gap parameters. Then, the roundabout is dynamically simulated. The simulation results in a revised set of gap parameters that are in turn used as inputs to a second trial of the capacity model, and in turn fed back into the simulation. The two steps are repeated until the parameters reach a pre-selected convergence criterion, so that gap parameter values for both the static capacity and dynamic microsimulation models are in equilibrium. Therefore, the applied procedure can conduct both static and dynamic roundabout design, usually applied separately. One can start with default values in guidelines and couple them with limited field data, improving both the expected results and cost-effectiveness of solutions. Next, safety is estimated using dynamic simulation software and a compatible conflict counting model to acquire surrogate measures of safety. Level-of-serviceand surrogate safety indicators for the existing and redesigned roundabouts are then compared. The procedure is first demonstrated on an old “ultra-large” roundabout. The procedure is tested on this roundabout using the Highway Capacity Manual 2016 (HCM2016), AimsunTM, and Surrogate Safety Assessment Model (SSAM) software. A redesign is shown to be far superior in efficiency and safety. Finally, two cases are described where large first generation roundaboutswere upgraded to modern standards.</p

The Development of Deep and Short Sea Shipping Container Routes Departing from Italian Ports

In this paper, an analysis of the development of Deep Sea Shipping (DSS) and Short Sea Shipping (SSS) container routes calling at Italian ports, is carried out. Data about DSS routes have been collected in the years: 2011, 2014, 2018 and 2019, while data about SSS services have been collected in 2010 and 2018. Italian ports have been classified as follows: Ligurian multi-port gateway cluster, formed by Leghorn, La Spezia, Genoa, Savona/Vado Ligure; Northern Adriatic multi-port gateway cluster, made up of Ancona, Ravenna, Venice and Trieste; Campanian multi-port gateway cluster, composed of Naples and Salerno; hub ports, i.e. Gioia Tauro, Cagliari (only until 2018) and Taranto (only until 2014). The most important gateway cluster, for both DSS and SSS services, is the Ligurian one, which includes Genoa, the major Italian container gateway port. Genoa has shown an almost constant increase in container traffic in the time period analyzed. Italian hub ports are also an important group, but they have registered a negative trend in the years under analysis. DSS routes, to Far East and the American Continent, usually call at the Ligurian ports and the hub port of Gioia Tauro. Northern Adriatic ports are crossed by only a few DSS routes, but they are crossed by a large number of SSS routes, especially feeder ones, with transshipment mainly in the hub ports of Gioia Tauro, Marsaxlokk, Piraeus and Port Said. The evolution of DSS services shows clearly the effects of naval gigantism phenomenon: the number of DSS services has decreased, but the total and, especially, the average DWT have increased. As regards SSS routes, also their frequencies have decreased, but their length and, in particular, the number of ports called, have increased: this choice is performed by container operators in order to increase the ships ’load factor’

Evoluzione della rete italiana delle autostrade del mare

Le Autostrade del Mare sono dei servizi di trasporto marittimo a corto raggio (Short Sea Shipping) che hanno fondamentalmente i seguenti obiettivi: costituire una valida alternativa al trasporto di tipo “tuttostrada”; ed integrare i trasporti terrestri, in particolare quando esistono dei vincoli geografici. In questa nota, dopo alcune osservazioni sulla competitività dei servizi di trasporto intermodale basati sulle Autostrade del Mare, rispetto ai servizi di trasporto “tutto-strada”, si analizza lo sviluppo delle rotte da e per i porti italiani. Lo studio mette in evidenza che le rotte delle Autostrade del Mare, fra coppie di porti italiani sulla penisola, non rappresentano, almeno attualmente, un’alternativa efficace al trasporto “tutto-strada”; anche se vi sono dei segni di una inversione di tendenza. Le rotte nazionali delle Autostrade del Mare infatti integrano i collegamenti fra la penisola e le isole; le rotte internazionali delle Autostrade del Mare collegano, fondamentalmente, i porti adriatici con porti della penisola balcanica, in particolare quelli posti sull’altra sponda dell’Adriatico, e i porti tirrenici con i porti, europei e nord africani, del Mediterraneo Occidentale. La nota mette infine in evidenza l’evoluzione delle caratteristiche dei servizi delle Autostrade del Mare negli anni 2008, 2010 e 2012. Seguono alcune considerazioni: sulla competitività del traspoto intermodale, basato su Autostrade del Mare, rispetto al tutto-strada ed sulle azioni relative ad azioni di policy volte a migliorare questa competitività