Procedure for the Identification of Existing Roads Alignment from Georeferenced Points Database

Reliability of Historical Car Data for Operating Speed Analysis along Road Networks

In recent years, innovative progress in information and communication technology (ICT) has introduced new sources for traffic data collection and analysis. On-board sensors like GPS-GPRS boxes, generally installed for insurance purposes, communicate information from circulating vehicles to data centers. Geographic location, date and time, vehicles’ speed and direction, are systematically transmitted and stored as Historical Car Data (HCD) from probe vehicles in the traffic stream. These databases provide a good opportunity to analyze the vehicles’ motion both in the temporal and spatial domains. The aim of this study is to pay attention to the reliability of this kind of data gathering. Since instrumented vehicles account for a small percentage of the entire vehicle fleet, it is important to understand if they can be considered as a sample representative of the whole population. The paper presents a comparison of speed data obtained from HCD with the ones recorded by inductive-loop detectors and microwave radar sensors; the performed analysis required the definition of specific methodologies and procedures. The obtained results show a high correspondence between the two sets of data. Therefore, HCD can be proposed for the detailed monitoring of, and studies on, the operating conditions of mobility along road networks.

Consistency of Urban Roads to Manage Emergencies: Methodology to Identify the Minimum Network with Total Connectivity at Maximum Availability

Natural disasters happen without warning; it is normally impossible to predict when they will occur, but it is necessary that rescue services reach the disaster site and manage the emergency. This paper proposes an innovative methodology to summarize seismic effects on road, building, and land factors in urban areas. The existing road network is modelled through the graph theory: the arcs represent the main infrastructures, while the nodes represent both the primary strategic buildings and the intersections between the main roads. Therefore, the quantitative approach takes into account the existing road network, the focal areas that play a strategic role during emergency, and their relationship with buildings and territory. The results enable the identification of the minimum urban structure (MUS) with total connectivity at maximum availability. These structures were composed of the paths that will be the priority choice for emergency vehicles after an earthquake. The proposed approach has been implemented to identify the MUS in a medium-size Italian urban center (Pomezia) in the event of a critical earthquake. The methodology is easy to apply and could represent an ideal tool in the preliminary phase of analysis of an urban road network to define new city plans through targeted territorial design, to facilitate decision makers in investment choices, to increase the road network consistency, and to implement emergency plans after natural disasters.

Cyclists at Roundabouts: Risk Analysis and Rational Criteria for Choosing Safer Layouts

Cycling for transportation is an important resource to reduce urban traffic congestion, enhance personal health, reduce energy consumption, and improve air quality, and the safety of cyclists in the cities is becoming a topic of growing interest. As shown in the literature, an important number of cyclist fatalities is due to road crashes occurring at urban intersections. This study combines a probabilistic and a damage model to perform a risk analysis for the collisions between motor vehicles and bicycles in the merging and diverging conflict points of a single-lane conventional roundabout with four arms, characterized by a permanent traffic flow. The probabilistic model is based on Poisson’s law and is aimed to measure the probability of a collision between bikes and motor vehicles within the elementary unit of exposure in each conflict point of the roundabout. The damage model exploits the reaction time of a road user to avoid a collision and has been built to develop a danger classification for the conflict points. The goal of this study is then to estimate the so-called risk of collision at the roundabout, to compare different possible layouts for various traffic volumes with increasing bike flows and geometric configurations, and to identify the most effective solutions to improve safety for cyclists. The results demonstrate the risk reduction given by a roundabike compared to a standard layout where cyclists and motor vehicles share the circulatory roadway. Therefore, the study here presented could help road managers to implement mitigation strategies taking into consideration both geometric and functional constraints.