Raffaele Mauro

Comparative Analysis of Compact Multilane Roundabouts and Turbo-Roundabouts

This paper presents a comparative analysis of the traffic performances of turbo-roundabouts and roundabouts in terms of capacity and delays. We chose to use a recent German procedure for roundabouts included in “Kreisel” software as our calculation procedure to determine the capacity of turbo-roundabouts. We found that the capacities of turbo-roundabout secondary entries were higher than roundabout capacities when the traffic flow in the inner lane of the circle is high and the traffic flow in the outer lane of the circle is in the low to lower-middle range. On the contrary, the capacities of the main entries to roundabouts are always higher than the capacities of the main entries to turbo-roundabouts. Taking into account the arithmetic or weighted mean behavior of the four entries, the total capacities of turbo-roundabouts, at both saturated and undersaturated conditions, are, in most cases, higher than the total capacities of roundabouts. In most of the important practical situations analyzed, delays we...

Traffic simulation models calibration using speed-density relationship

Calibration of traffic models.Calibration as optimization problem.Use of genetic algorithm. This paper presents the first results of a research which applied a genetic algorithm to calibrate a microscopic traffic simulation model based on speed-density relationships. A large set of traffic data collected from the A22 Freeway, Italy, was used and a comparison was performed between the field measurements and the simulation outputs obtained for a test freeway segment by using the Aimsun microscopic simulator.The calibration was formulated as an optimization problem to be solved based on a genetic algorithm; the objective function was defined in order to minimize the differences between the simulated and real data sets in the speed-density graphs. For this purpose, the genetic algorithm tool in MATLAB?was applied.Keeping in mind the objective to automatize this process, the optimization technique was attached to Aimsun via a subroutine, so that the data transfer between the two programs could automatically happen. An external script written in Python allowed the MATLAB?software to interact with Aimsun software.A better match to the field data was reached with the optimization parameters set with the genetic algorithm. In order to check to what extent the model replicated reality, model validation was also addressed. Results showed that a genetic algorithm is usefully applicable in the calibration process of the microscopic traffic simulation model. Beneficial effects are expected by applying the suggested optimization technique since it searches for an optimum set of parameters through an efficient search method.

Model of Potential Crash Rates of Rural Roundabouts with Geometrical Features

In recent years, there has been a widespread diffusion of roundabout intersections in the Italian road network; their undoubted popularity is attributable not only to their proven performance in terms of safety but also to their guarantee of smooth traffic flow. However, safety-related requirements of geometric designs are occasionally placed in a subordinate position; therefore, the success achieved by some foreign experiences has not been reached in every area. A model of potential crash rates may indicate how to modify the geometry of intersections to ensure safety. With regard to this, an example model based on the conflict opportunity technique has been developed for estimating crash rates at rural roundabouts. The model appears to respond well to traffic conditions and the geometry of roundabouts. Development of the model and results are described and analyzed in this paper.

A simplified model for railway catenary wire dynamics

In this paper, a simplified analytic model for the dynamic behaviour of railway catenary wire is presented. The model is discussed and validated with the help of numerical results obtained by a finite element code, for the case of a typical Italian railway installation. The simplified model is convenient from the computational point of view and is useful for sensitivity analysis. Some parametric studies have been developed by considering as free parameters the velocity and the distance of the train pantographs and looking at their effect on catenary dynamics.

Operating Speed Prediction Models for Sustainable Road Safety Management

Road safety management may be improved if quantitative assessment of safety levels is carried out. One of the most frequent roadway characteristics that affect crashes is the geometric alignment. Many highway design standards in the world have introduced rules to assess the alignment consistency. In this paper we report an experimental analysis conducted in 2010 on statistically significant number of roadway sections belonging to two - lane rural highways in Northern Italy. The aim of this research is to develop operating speed prediction models on tangents and circular curves. Acquired relationships were particularly interesting and different explanatory variables were introduced in the predictive models which are dependent on examined geometric roads features. These relationships constitute a new set of models about the operating speeds to design and verify geometric highways alignments adding to those already available in the scientific literature.

Common Random Processes

We present here a number of random processes which are interesting as such and will be used in later chapters.

Time Headway Process

The time headway process has great practical as well as theoretical significance in highway engineering. The chapter deals with the basics which statistically characterize a process of time intervals between vehicles of a traffic stream. Some aspects of the correspondence between headways and counting distributions are also outlined

Introduction to Random and Traffic Processes

The chapter gives a plain introduction to random and traffic processes. The knowledge of random processes is an essential prerequisite to studying the second part of this book, which is concerned with some fundamental topics in traffic modelling.

Random Process Fundamentals

The chapter deals with the basic notions that characterize a random process in a statistical sense.

Traffic Flow Stationarity

Defining stationary flow conditions is one of the main topics for practical applications in traffic engineering.