1,721,010 research outputs found
Valutazione della Sicurezza delle Strade Extraurbane a Carreggiata Unica - Il Progetto Europeo IASP
No full textIdentification of Hazard Location and Ranking of Measures to Improve Safety on Local Rural Roads (IASP)
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Safety Index for Evaluation of Two-Lane Rural Highways
No full textThe methodological approach to safety evaluation of two-lane rural highway segments that is presented uses both analytical procedures referring to alignment design consistency models and safety inspection processes. A safety index (SI) that quantitatively measures the relative safety performance of a road segment is calculated from the procedure. The SI is formulated by combining three components of risk: the exposure of road users to road hazards, the probability of a vehicle's being involved in an accident, and the resulting consequences should an accident occur. This systematic and replicable procedure integrates two different, complementary approaches—one based on design consistency evaluations and the other on safety inspections—and makes it possible to address a wide variety of safety issues effectively. A further advantage of the procedure is its applicability on highways where crash data are either not available or unreliable. Validation of the procedure was carried out on a sample of roads by a comparison of the risk rank obtained by using the SI and accident history. The SI was assessed in 30 segments chosen from a sample of two-lane rural highways in Italy, and the actual accident situation was obtained with the empirical Bayes (EB) procedure. Spearman's rank correlation was used to determine the level of agreement between the rankings obtained with the two techniques. The results from the Spearman's rank-correlation analysis validate the SI, indicating that the ranking from the SI scores and the EB estimates agrees at the 99.9% level of significance with a correlation coefficient of 0.87
Safety Evaluation Process for Two-Lane Rural Highways
No full textIn the contest of the EU program “ Road Safety in EU: the 1997-2001 program”, the “IASP” project, proposed by the Province of Catania with the scientific support of the Department of Civil and Environmental Engineering of University of Catania, was approved and co-funded by European Commission (DG TREN). A methodological approach for the safety evaluation of two-lane rural highway segments that uses both analytical procedures referring to road safety inspection processes and alignment design consistency models is presented. Road safety inspections (RSI) are recognized as an effective tool for identifying safety issues. However, due to the subjective nature of the process, they may give rise to disagreements which limit their effectiveness. A RSI procedure aimed at improving the effectiveness and the reliability of the methodology was defined. Many studies show that safety evaluations based on the analysis of alignment design consistency can be effective in identifying hazardous road locations. The proposed approach makes use of theoretical-experimental models for the evaluation of alignment design consistency. A safety index (SI) that quantitatively measures the relative safety performance of a road segment is calculated from the procedure. The SI is formulated by combining three components of risk: the exposure of road users to road hazards, the probability of a vehicle being involved in an accident and the resulting consequences should an accident occur. Validation of the procedure was carried out on a sample of roads by a comparison of the risk rank obtained using the SI and accident history. The SI was assessed in 30 segments chosen from a sample of two-lane rural highways in Italy and the actual accident situation was obtained with the EB procedure. Spearman’s rank-correlation was used to determine the level of agreement between the rankings obtained using the two techniques. The results from the Spearman’s rank-correlation analysis validate the SI, indicating that the ranking from the SI scores and the EB estimates agree at the 99.9% level of significance with a correlation coefficient equal to 0.8
Valutazione dei fattori di rischio degli attraversamenti pedonali mediante analisi di sicurezza e analisi dei conflitti
No full textAi fini del miglioramento delle condizioni di sicurezza dei pedoni, le tradizionali strategie di intervento basate sull’individuazione dei siti ad elevata incidentalità e sull’implementazione di misure di messa in sicurezza in questi siti non sempre sono efficaci sia perché intervengono solo a posteriori dopo il verificarsi di incidenti sia perché l'incidentalità pedonale è in genere diffusa sul territorio, rendendo non sempre affidabile l’analisi statistica degli incidenti. Un efficace approccio preventivo è basato sulle analisi di sicurezza, anche se, nonostante l’intensa attività di ricerca, queste ultime non sono ancora sufficientemente oggettive e non consentono, utilizzate da sole, l’elaborazione di misure quantitative correlate con l’incidentalità. Al fine di ridurre il grado di soggettività della procedura, nell’articolo si presenta una metodologia di individuazione dei fattori di rischio pedonale che associa le analisi di sicurezza e l’analisi dei conflitti di traffico. Un conflitto è una situazione osservabile nella quale due o più utenti si avvicinano nello spazio o nel tempo con un’ampiezza tale da creare un rischio di collisione se i loro movimenti rimangono inalterati. I conflitti rappresentano una misura surrogata della sicurezza e presentano una più elevata frequenza rispetto agli incidenti consentendo misure quantitative significative. Nel presente studio sono stati utilizzati come indice del livello di sicurezza da confrontare con l’indice di rischio calcolato in un campione di 51 attraversamenti pedonali in ambito urbano
A Procedure to Improve Safety Inspections Effectiveness and Reliability on Rural Two-Lane Highways
No full textRoad Safety Inspections (RSI) are recognized as an effective tool for identifying safety issues. However, due to the subjective nature of the process, they may give rise to disagreements which limit their effectiveness. In the framework of the IASP research program sponsored by European Commission, which is focused on rural two-lane highways, a RSI procedure aimed at improving the effectiveness and the reliability of the methodology has been defined. For this purpose, the research has been pinpointed on the inspection framework, on the inspectors and client roles and, with special emphasis, on the methodologies used for identifying and ranking the safety problems. In order to test the reliability of the methodology, the agreement of the results of the safety issues ranks produced by different inspectors has been addressed. Specifically, the statistic kappa has been used. Results show that there is a statistically significant level of agreement among inspectors for the majority of the safety issues. The reliability of the procedure is satisfactory, specially if it is considered that the identification of the safety issues is a very complex task based on human evaluations and expertise not supported by instrumental measures
Una procedura per il miglioramento dell’efficacia e dell’affidabilità delle ispezioni di sicurezza delle strade esistenti
No full textL’analisi delle condizioni di sicurezza sulle infrastrutture viarie in esercizio è ormai diventata una fase fondamentale nel sistema di gestione della rete stradale, per la gravità oggettiva del fenomeno in termini di perdite di vite umane. Un approccio complessivo al problema dell’individuazione delle cause di rischio per le strade esistenti dovrebbe prevedere, accanto all’utilizzo dell’analisi dell’incidentalità, l’applicazione delle ispezioni di sicurezza (Road Safety Inspections). A tal fine, la ricerca condotta dagli autori, nell’ambito di un progetto svolto per conto della Provincia di Catania con il cofinanziamento della Comunità Europea, ha posto l’attenzione sulla strutturazione della procedura di ispezione, sui ruoli dell’Ente Gestore e degli esperti puntando alla definizione e alla formalizzazione delle metodologie di identificazione e di quantificazione dei problemi di sicurezza al fine di fornire uno strumento direttamente operativo per l’esecuzione delle analisi. Inoltre, sono state definite le diverse fasi delle ispezioni di controllo, e per ogni fase, gli obiettivi, le attrezzature necessarie, la metodologia ed i ruoli di ogni esperto del team di ispezione. Sono state opportunamente progettate e messe a punto dettagliate liste di controllo, riguardanti le principali problematiche di sicurezza che possono essere presenti con continuità lungo le strade analizzate, e moduli di controllo dei siti specifici, differenziati per segmenti e intersezioni. Inoltre, al fine di verificare l’affidabilità della metodologia proposta, la corrispondenza tra i giudizi espressi da differenti gruppi di esperti è stata verificata con un test statistico di concordanza. Come risultato della ricerca è stato redatto un manuale per l’esecuzione della procedura
Crash modification functions for pavement surface condition and geometric design indicators
No full textThe combined contribution to highway safety of pavement surface and geometric design indicators is not well investigated due to the complexity of data collection and high time variability of pavement surface conditions. Introduction of high efficiency equipment for comprehensive road surveys is mitigating this issue, expanding possibilities of data integration. In this framework, the present study developed crash modification functions (CMFs) of pavement surface and geometric design indicators for different crash types (total, run-off-the-road, and others), pavement conditions (dry and wet), and lighting conditions (daytime and nighttime) based on data from two-lane rural highways in Italy. Geometric and pavement data were surveyed with the Automatic Road Analyzer and the Grip Tester. Pavement surface condition data were corrected to the crash time by pavement performance deterioration models based on traffic load to account for the variation in pavement conditions over time. Crash, traffic and weather data were retrieved from national and local databases. This study used safety performance functions (SPFs), fitted with generalized linear modelling techniques and a negative binomial distribution error structure, for developing CMFs. The SPFs were used to quantify the effect of a specific variable on crash occurrence and CMFs were then derived from the model coefficients. CMFs were developed for the following parameters: Grip Number, International Roughness Index, curvature change ratio, coefficient of variation of the curvature, maximum superelevation deficiency, and minimum lane width. According to the study results, an increase in friction, as measured by the Grip Number, is associated with a reduction in crash frequency while an increase in roughness, as measured by the International Roughness Index, is associated with an increase in crash frequency. Thus, both pavement maintenance treatments aimed at increasing friction as well as treatments aimed at reducing irregularities have a positive safety effect, especially when wet, run-off-the-road or nighttime crashes are overrepresented. Study results allow to effectively integrate pavement management systems and safety management systems. When developing paving schedules, transportation agencies often base their decisions on asset management condition targets but do not explicitly account for the role of pavement conditions in highway safety. Availability of CMFs for both pavement surface parameters as well as geometric design parameters is crucial to improve pavement and geometric characteristics considering their safety effects
Comparison of in situ devices for the assessment of pavement subgrade stiffness
Full text linkThe subgrade is the top surface of a roadbed upon which the pavement structure is constructed. The purpose is to provide a platform for construction of the pavement and to support the pavement without unwanted deflection that would reduce its performance. For those reasons subgrade bearing capacity have to be investigate during the construction process as a quality control, based on the design results. The dynamic in situ Falling Weight Deflectometer (FWD) tests are nowadays widely used and considered the most reliable and suitable approach to determine bearing capacity of road pavements and elastic moduli. In addition, the use of the Light Weight Deflectometer (LWD) takes the advantage of the dynamic application of load, and the flexibility of the handling of the equipment on construction area and unbound layer. In the present paper, a wide literature review is presented on the topic of correlation between different subgrade bearing capacity in situ tests. In order to assess the transferability of LWD measures, these results were compared with FWD test and Dynamic Cone Penetrometer (DCP) test. Soil samples, taken from the site, have also been investigate in laboratory to relate geotechnical and in situ test results
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