Search results for "Roundabouts"

Passenger Car Equivalent for Heavy Vehicles Crossing Turbo-roundabouts

2016

Abstract Turbo-roundabouts represent an innovative scheme of modern roundabouts which provides a spiraling traffic flow and requires drivers to choose their direction before entering the intersection, since raised lane separators mark the lanes on the ring. The configuration of the turbo-roundabout makes that patterns of conflict at entries with one and two conflicting traffic streams can coexist. This paper presents research efforts aimed at measuring quantitatively the effect of heavy vehicles on operational conditions of a turbo-roundabout. The study starts from the initial belief that the greatest constraints to the vehicular trajectories imposed by the turbo-roundabout necessarily impl…

Application of a genetic algorithm in calibration of traffic microsimulation models

2017

This chapter describes the genetic algorithm-based calibration procedure for a microscopic traffic simulation model focusing on freeways and modern roundabouts. For both case studies, the genetic algorithm tool in MATLAB® was applied in order to reach the convergence between the outputs from Aimsun microscopic simulator and the observed data. The automatic interaction with Aimsun software was implemented through an original external Python script. Results showed that the genetic algorithm-based calibration procedure gave a better match to the observed data than simple manual calibration and the efficiency of the calibration efforts resulted significantly improved. At last, the calbrated mod…

Cost-benefit analysis of road safety measures

2013

Road accidents represent one of the most serious problems faced by the Ministries of Public Health in the World. In Italy for example, in the year 2007 there were almost 330, 000 injuries and 5, 131 fatalities; 230, 871 crashes in all which resulted in an estimated € 30.4 billion financial loss, corresponding to 2% of GDP. In 1999 the National Road Safety Plan (NRSP), among other things, funded the requalification of several unsafe road infrastructures at higher risk of accidents. Unlike other infrastructure investment plans, NRSP usually requires: i) specific safety analysis of crash history to identify the critical road; ii) proactive action, e.g. RSAs and RSARs; iii) before-after acciden…

An Italian experience on crash modeling for roundabouts

2015

In the last few years a considerable amount of safety models and evaluation tasks have been developed and specifically dedicated to roundabouts. Several safety performance functions (SPFs), indeed, have been implemented for roundabouts worldwide. Since SPFs are developed using crashes, traffic volume and other characteristics of a specific site (or geographical area), their direct transferability to other contexts different from those in which SPFs were calibrated is not always possible and, in any case, it must be done very carefully. A safety performance function cannot be used without a transferability evaluation for sites not included in the geographic area for which it was developed. S…

Safety evaluation of turbo roundabout with and without internal traffic separations considering autonomous vehicles operation

The paper presents a microsimulation approach for assessing the safety performance of turbo-roundabouts where Cooperative Autonomous Vehicles “CAVs” have been mixed with conventional vehicles “CVs”. Based on the analysis of vehicle trajectories from VISSIM and subsequent analysis of traffic conflicts through the Surrogate Safety Assessment Model (SSAM), the research aims to evaluate the safety benefits of turbo-roundabouts where the lanes are physically separated by raised curbs compared to roundabouts without curbs. The paper shall also lead to describe the methodological path followed to build VISSIM models of turboroundabout with and without raised curbs, to calibrate the simulation mode…

Safety Evaluation of Turbo-Roundabouts with and without Internal Traffic Separations Considering Autonomous Vehicles Operation

2021

The paper presents a microsimulation approach for assessing the safety performance of turbo-roundabouts where Cooperative Autonomous Vehicles “CAVs” have been introduced into the traffic mix alongside conventional vehicles “CVs”. Based on the analysis of vehicle trajectories from VISSIM and subsequent analysis of traffic conflicts through the Surrogate Safety Assessment Model (SSAM), the research aims to evaluate the safety benefits of turbo-roundabouts where the lanes are physically separated by raised curbs, compared to roundabouts without such curbs. The paper will then describe the methodological path followed to build VISSIM models of turbo-roundabouts with and without raised curbs in …