1,721,015 research outputs found
Traffic modeling for wildland-urban interface fire evacuation
No full textSeveral traffic modeling tools are currently available for evacuation planning and real-time decision support during emergencies. This paper reviews potential traffic-modeling approaches in the context of wildland-urban interface (WUI) fire-evacuation applications. Existing modeling approaches and features are evaluated pertaining to fire-related, spatial, and demographic factors; intended application (planning or decision support); and temporal issues. This systematic review shows the importance of the following modeling approaches: dynamic modeling structures, considering behavioral variability and route choice; activity-based models for short-notice evacuation planning; and macroscopic traffic simulation for real-time evacuation management. Subsequently, the modeling features of 22 traffic models and applications currently available in practice and the literature are reviewed and matched with the benchmark features identified for WUI fire applications. Based on this review analysis, recommendations are made for developing traffic models specifically applicable to WUI fire evacuation, including possible integrations with wildfire and pedestrian models
Route Familiarity in Road Safety: Theory and Applications
Full text linkHuman factors are closely related to the causation of road accidents. Among them, the route familiarity plays an important role, since it can influence the driving task. The relationships between route familiarity and road safety are explored in this thesis from both a theoretical and an application point of view.
A general background section is devoted to the explanation of all those possible relationships, as reported in literature. They concern the influence on the driving task, the driver behaviour, the perceived risk, the performances, the travel utility. A specific section is devoted to the practical involvements in road design and traffic engineering.
The research work was focused on four different but parallel aspects connected to the main topic. The evolution of speeds and trajectories was inquired through the use of experimental data. The same data were used to investigate the possible changes in drivers’ perception. The potential impact of route familiarity on road accidents was firstly analyzed from a theoretical point of view based on exisiting frameworks. Thereafter, it was analyzed based on a traffic and accident database acquired in Norway, through different research steps.
The highlighted relationships between route familiarity and road safety were used to draw conclusions and propose potential developments related to the road safety practice. Moreover, given the several measures of familiarity found in previous literature, a more detailed and unified definition for measuring familiarity was proposed. It is based on both time and distance scales, according to previous theories and findings
Route familiarity in road safety: A literature review and an identification proposal
Full text linkRoute familiarity can be an important safety-related variable, which is often neglected. A review of previous works highlighting the relationships between route familiarity and road safety in behavioural studies and engineering standards/frameworks has been conducted. Theoretical frameworks supported by experimental results have revealed that driving behaviour can be affected by route familiarity. The latter may lead to distraction and self-confidence; and in turn to more dangerous behaviours after repeated journeys. From an economic perspective, the possible worsening of driving safety performance may be explained by trade-offs with mobility benefits. Route familiarity is also considered in engineering practice. Road design guidelines assuming a “design driver” were suggested as implicitly preserving the safety of familiar/unfamiliar drivers. The mix of familiar and unfamiliar drivers in traffic flow is explicitly considered when computing the design traffic. The safety implications of these matters find only partial confirmation in previous studies focused on involvement in crashes. However, comparing those findings was difficult due to the high variability in measuring the route familiarity itself. An attempt to harmonize the possible identifications of familiarity for future studies, based on previous findings, is proposed. The proposal considers two different scales used for measuring route familiarity: one based on travelling frequency, the other on distance from residence
Road design influence on driving behaviors: The influence of curve design, a case study
Full text linkRoad geometry has always been a key feature for road safety concerns. It will become more crucial in the context of future transportation, especially with the advent of Connected and Autonomous Vehicles (CAVs). In fact, recognizable and intuitive road alignments would simplify the driving tasks for both humans and CAVs (independently from the rate of automation). Thus, not only building consistent and self-explaining roads is fundamental for new and old vehicles, but also adjusting the existent ones, operation that seems even harder. Since most of the existing roads would need massive interventions, policy makers and road designers might choose between making adjustments being compliant with the current regulations in toto or adopting countermeasures supported by specific safety assessments to make existing roads safer, also in the perspective of future changes. In this optic, the present study tries to investigate a typical geometric design issue of existing roads, i.e., the presence of a long segment followed by a sharp curve without transition curves on undivided two-way two-lane rural roads. This alignment does not reflect the current recommendations for road alignment, so it was investigated the effect of such a design on users and safety for a specific testbed. The users’ behavior was investigated recording the kinematic parameters of the traveling vehicles. This data collection was run using radar traffic counters, placed on the roadside throughout the entire layout of the investigated segment-curve, to get speed and acceleration. The data were elaborated to investigate driving behavior in free-flow conditions. A K-means cluster analysis was run to characterize the users’ behaviors in terms of speed and acceleration. Hard braking was found to be strongly related to high speed, as well as ongoing deceleration on curve was detected for all the vehicles with high speeds on the segment. Results about users’ behaviors were compared to the available crash dataset to understand the possible implications of human factors on occurred crashes and to simulate the decision process of safety-related adjustments of existing roads
Proposal of a New Method to Analyze the Road Safety Conditions Related to Friction
No full textThis paper represents a new method to analyze the problem of friction of road vehicles. Starting from the 3rd criterion of Lamm, the new concept of “Friction Capital” was introduced as the limit performance of the road in terms of friction. The method has been implemented in a software package called Design Skid Resistance (DSR), which reliability is tested providing the reconstruction of eight real skidding accidents. The output of the DSR is the Friction Diagram that represents the percentage of “Friction Capital” that a vehicle is using traveling on a given road. This percentage is defined as FUSED. During the design step, the Friction Diagram could be used in order to quantify the risk of skidding related to a given road layout. In this paper, the authors provide an example of DSR application to an Italian rural road, and investigate the influence of the vehicle type on the Friction Diagram, since it was observed that the type of vehicle used in analyzing a road segment makes the values of FUSED change when the boundary conditions and the road geometry change
A safety assessment planning strategy proposal within the context of sustainable Urban mobility Plans: How to account for Connected and Autonomous vehicles in safety analysis in the SUMP?
No full textIn the context of Sustainable Urban Mobility Plans (SUMP), when road safety assessments are dealt with, different future scenarios are considered weighing the positive impacts of the proposed strategies for improving the transport system and road safety, globally. However, while considering those future scenarios, until now, the chance that Connected and Autonomous Vehicles (CAVs) will be introduced in the market has never been accounted. Neglecting CAVs can provide misleading results in terms of safety assessment. In this study, a general framework about how to include CAVs in SUMP safety assessments is provided. The general framework, which relies on traffic simulations and algorithms to count conflicts, was tested on two-way two-lane rural roads within the Province of Bari (Italy), where a SUMP was recently developed but the possible introduction of AVs has not been accounted, as it is a common practice in SUMP drafting. Results provided by simulations show a dramatic crash reduction when the traffic is made only of CAVs, while more dangerous situations are highlighted in the case of mixed traffic. Therefore, some countermeasures to handle mixed traffic, such as e.g., reserved lanes for CAVs in case of new roads, must be found and provided for stakeholders and practitioners while dealing with planning strategies
Optimal planning of safety improvements on road sites belonging to different categories within large networks: An integrated multi-layer framework
Full text linkPlanning road safety interventions on large road networks implies several layers of complexity in the decisionmaking process. In fact, the following simultaneous problems should be addressed: estimating safety performances on the different road elements of the network, identifying sites showing high potential for improvement with respect to reference values, defining the possible types of safety measures to be implemented and their anticipated effect on traffic safety, limiting the number of interventions given fixed budget constraints. This study proposes an integrated multi-layer framework which takes into account the above-defined problems into a single optimization procedure which provides the number and type of safety interventions to be implemented over a wide road network composed of different categories of road elements. The proposed framework is based on the following peculiar aspects: the potential for safety improvement is quantitatively assessed based on the estimation of safety performances for each road category, a bi-level thresholding process integrated in the optimization process is used to highlight sites for interventions, the anticipated outcome of safety measures is quantitatively assessed as well through available crash reduction factors. The proposed methodology is applied to a case study which analyzes a sample of real roads belonging to a province-wide road network composed of various road elements (i.e., different categories of segments and intersections), under different budget constraints. Results demonstrate the applicability and flexibility of the proposed approach, which could be used for planning purposes, independently of the particular geographic location. Clearly, the approach is valid at the planning stage, given that several details of the different layers of analysis are necessarily simplified, while they should be studied in detail at the single intervention project stage
Sicurezza stradale : un approccio scientifico a un problema tecnico e comportamentale
No full textTutti i governi dei Paesi dotati di una consolidata rete stradale stanno orientando i propri investimenti in opere pubbliche, non più quasi esclusivamente su nuove infrastrutture stradali ma piuttosto sull’adeguamento di quelle esistenti, in particolare tenendo conto della sicurezza stradale. In quest’ultimo settore la ricerca internazionale è molto attiva e ultimamente si stanno facendo molti passi in avanti, anche se non è stato ancora individuato un modello teorico in grado di spiegare tutte le evidenze sperimentali, talvolta contrastanti, emerse nei vari ambiti. Probabilmente la difficoltà di integrare le conoscenze tecnico-ingegneristiche con quelle sul comportamento umano sta ritardando la comprensione completa dei fenomeni in gioco. Tuttavia, sia a livello dei singoli stati (con la principale eccezione degli USA) e sia a livello internazionale, generalmente non è stato raggiunto un protocollo operativo, tecnico e normativo, per procedere alla progettazione ed esecuzione dell’adeguamento alla sicurezza delle infrastrutture stradali esistenti.
Questo testo vuole rappresentare un contributo in questo senso, rivolto in particolare al caso dell’Italia ma con un metodo che potrebbe facilmente essere esteso a qualunque stato al di fuori degli USA.
Dopo i primi capitoli dedicati alla Misura della Sicurezza Stradale (cap. 2) e alle descrizione delle principali Teorie di Incidentalità e Modelli Comportamentali (cap. 3), il testo affronta i concetti basilari della Incidentalità e del Rischio (cap. 4) con un approfondimento sulla importanza degli Utenti Abituali e Non Abituali, descrivendo successivamente la Situazione Normativa in Italia al 2015 con le relative Linee Guida (cap. 5) e le relative Criticità (cap. 6). Viene poi esplicitato il metodo dell’Highway Safety Manual (HSM) attualmente utilizzando negli USA, riportando, con l’autorizzazione della AASHTO, le parti essenziali del Manuale (cap.7), per poi effettuare un confronto con le Linee Guida italiane (cap.8). Di seguito viene descritta una nuova metodologia, basata sulla definizione del Diagramma della Aderenza (cap. 9) ed uno dei principali metodi (quello del LOSS, Livello di Servizio della Sicurezza) attualmente utilizzati negli USA per effettuare la diagnosi di incidentalità (cap. 10). Infine viene proposto un nuovo protocollo di progetto per i tronchi stradali extraurbani (cap. 11), con la calibrazione per l’Italia del metodo HSM (cap. 12) e viene descritto un esempio completo di applicazione progettuale (cap. 13), prima di accennare ai possibili futuri sviluppi (cap. 14). Il volume è inoltre corredato di file elettronici per approfondimenti bibliografici e per agevolare le procedure di calcolo di progetto
Road design influence on driving behaviors: The influence of curve design, a case study
Full text linkRoad geometry has always been a key feature for road safety concerns. It will become more crucial in the context of future transportation, especially with the advent of Connected and Autonomous Vehicles (CAVs). In fact, recognizable and intuitive road alignments would simplify the driving tasks for both humans and CAVs (independently from the rate of automation). Thus, not only building consistent and self-explaining roads is fundamental for new and old vehicles, but also adjusting the existent ones, operation that seems even harder. Since most of the existing roads would need massive interventions, policy makers and road designers might choose between making adjustments being compliant with the current regulations in toto or adopting countermeasures supported by specific safety assessments to make existing roads safer, also in the perspective of future changes. In this optic, the present study tries to investigate a typical geometric design issue of existing roads, i.e., the presence of a long segment followed by a sharp curve without transition curves on undivided two-way two-lane rural roads. This alignment does not reflect the current recommendations for road alignment, so it was investigated the effect of such a design on users and safety for a specific testbed. The users’ behavior was investigated recording the kinematic parameters of the traveling vehicles. This data collection was run using radar traffic counters, placed on the roadside throughout the entire layout of the investigated segment-curve, to get speed and acceleration. The data were elaborated to investigate driving behavior in free-flow conditions. A K-means cluster analysis was run to characterize the users’ behaviors in terms of speed and acceleration. Hard braking was found to be strongly related to high speed, as well as ongoing deceleration on curve was detected for all the vehicles with high speeds on the segment. Results about users’ behaviors were compared to the available crash dataset to understand the possible implications of human factors on occurred crashes and to simulate the decision process of safety-related adjustments of existing roads
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