Papers by Carmelo D'Agostino
Negli ultimi anni, si è assistito anche in Italia ad una crescita esponenziale degli utenti dei n... more Negli ultimi anni, si è assistito anche in Italia ad una crescita esponenziale degli utenti dei navigatori satellitari, cioè quei dispositivi dotati di capacità di ricezione del segnale satellitare GPS (Global Positioning System) integrati con un sistema di mappe e database stradali, progettati per assistere i conducenti delle automobili in maniera interattiva attraverso il suggerimento sul percorso da seguire per raggiungere una destinazione impostata. Tale crescita è stata senz’altro favorita dal contemporaneo verificarsi di più condizioni vantaggiose, quali la riduzione dei costi, la disponibilità di dispositivi di navigazione integrati sui comuni smartphone, la semplicità di impiego.
Le nuove tecnologie basate sulla navigazione satellitare, inoltre, si stanno rapidamente evolvendo verso forme di assistenza anche per gli utenti non tradizionali dei navigatori satellitari, cioè i pedoni.
Sono stati infatti sviluppati sistemi di navigazione GPS che presentano funzioni sempre più orientate all’utenza pedonale.
Le funzioni privilegiate sono essenzialmente quelle di carattere turistico (per favorire il raggiungimento di luoghi di interesse storico-culturale quali monumenti, chiese, piazze, etc.), investigativo (per localizzare un obiettivo mobile durante operazioni in incognito da parte delle forze dell’ordine o di privati), lavorativo (ad es., per i corrieri che effettuano consegne nei centri pedonali). Di particolare interesse è poi la cosiddetta “funzione dell’ultimo miglio” che consente all’utente di registrare la posizione del proprio veicolo parcheggiato in modo tale da poterlo facilmente ritrovare una volta che si è di ritorno dal luogo raggiunto a piedi.
Il presente gruppo di ricerca, intende proporre un contributo verso lo sviluppo di un sistema di navigazione satellitare pedonale in cui vengano introdotte opzioni di scelta dei percorsi ottimali dal punto di vista del livello di sicurezza offerto dagli elementi componenti le infrastrutture stradali in ambito urbano. Attraverso l’approfondita caratterizzazione del livello di sicurezza garantito dai percorsi pedonali mediante opportuni indicatori prestazionali si vogliono creare i presupposti per una gestione interattiva dei flussi pedonali. In particolare, grazie al supporto dei Sistemi Informativi Territoriali integrati con la tecnologia GPS, è possibile prospettare scenari futuri in cui i pedoni siano avvisati in tempo reale in merito agli elementi della rete stradale (nodi e tronchi) in grado di offrire le migliori prestazioni in termini di sicurezza; il tutto, in coerenza con le esigenze prioritarie degli utenti, tradizionalmente espresse in funzione della lunghezza dei percorsi pedonali e dei tempi di percorrenza, e mettendo in conto anche le necessità delle categorie di utenti pedonali che manifestano condizioni di disagio aggiuntive quali gli anziani ed i disabili.
Il Sistema Informativo Territoriale per la gestione della sicurezza dei percorsi pedonali è stato... more Il Sistema Informativo Territoriale per la gestione della sicurezza dei percorsi pedonali è stato sviluppato nell’ambito dell’attività di ricerca condotta presso il Dipartimento di Ingegneria Civile e Ambientale dell’Università degli Studi di Catania. Il gruppo di ricerca, con questo progetto, intende porre le basi per la futura realizzazione di un sistema integrato SIT-ITS (Intelligent Transport System), mirato a garantire la gestione dinamica e la sicurezza dei flussi pedonali, attraverso l’utilizzo di dispositivi dislocati lungo il territorio.
A new European Union (EU) regulation for safety barriers, which is based on performance, has enco... more A new European Union (EU) regulation for safety barriers, which is based on performance, has encouraged agencies to perform an upgrade of the old barriers, with the expectation that there will be safety benefits at the retrofitted sites. The new class of barriers was designed and installed in compliance with the (European Norm) EN 1317 standards for Road Restraint Systems created in 1998, which lays down common requirements for the testing and certification of road restraint systems in all countries of the European Committee for Standardization (CEN). Both the older and new barriers are made of steel and are installed in such a way as to avoid vehicle intrusion, but the older ones are thought to be only effective at low speeds and low angles of impact. The new standard seeks to remedy this by providing better protection at higher speeds. The paper seeks to quantify the effect on the frequency of fatal+injury crashes of retrofitting motorways with barriers meeting the new standards, by performing an empirical Bayes before-after analysis based on data from the A18 Messina-Catania motorway in Italy. The results suggest a safety benefit, which, although statistically insignificant, is enough to recommend that the retrofits are cost-effective and should continue. However, the sample size needs to be increased in order to develop a statistically robust crash modification factor.
Road Agencies set quantitative targets and adopt related road safety strategies within the priori... more Road Agencies set quantitative targets and adopt related road safety strategies within the priorities and the available resources funds at a time of economic crisis. In this framework, benefit-cost analyses (BCA) are carried out to support the decision making process and alternative measures are ranked according to their expected benefit and benefit-cost ratio calculated using a Safety Performance Function (SPF) and Crash Modification Factors (CMFs) as predictor of future safety performances.
Due to the variance of CMFs and crash frequency we are uncertain what the benefits of some future actions will be. The chance of making a wrong decisions depends on the size of the standard deviation of the probability distribution of CMFs and SPF, as well.
To deal with the uncertainty inherent in the decision making process, a reliability based assessment of benefits must be performed introducing a stochastic approach. In the paper the variance of the CMFs and SPFs are taken into account in a reliability based BCA to address improvements and issues of an accurate probabilistic approach when compared to the deterministic results or other approximated procedures. A case study is presented comparing different safety countermeasures selected to reduce crash frequency and severity on sharp curves in motorway. These measures include retrofitting of old safety barrier, delineation systems, shoulder rumble strips and their combinations. The methodology was applied using Monte Carlo simulations to calculate the probability of failure of BCA statements. Results and comparisons with alternative approaches, like that proposed in the HSM, are presented showing remarkable differences in the evaluation outcomes that can be achieved.
Safety performance functions (SPFs) are crucial to science-based road safety management. Success ... more Safety performance functions (SPFs) are crucial to science-based road safety management. Success in developing and applying SPFs depends fundamentally on two key factors: the validity of the statistical inferences for the available data and on how well the data can be organized into distinct homogenous entities. The latter aspect plays a key role in the identification and treatment of road sections or corridors with problems related to safety. Indeed, the segmentation of a road network could be especially critical in the development of SPFs that could be used in safety management for roadway types, such as motorways (freeways in North America), that have a large number of variables that could result in very short segments if these are desired to be homogeneous. This consequence, from an analytical point of view, can be a problem when the location of crashes is not precise and when there is an over abundance of segments with zero crashes. Lengthening the segments for developing and applying SPFs can mitigate this problem, but at a sacrifice of homogeneity. This paper seeks to address this dilemma by investigating five approaches for segmentation for motorways, using sample data from Italy. The best results were obtained for the segmentation based on two curves and two tangents within a segment and the segmentation with fixed length. The segmentation characterized by a constant value of all original variables inside each segment was the poorest approach by all measures.
Black spot ranking is an important tool for finding the sites with potential safety improvement o... more Black spot ranking is an important tool for finding the sites with potential safety improvement on the road network. The EU Directive on Road Infrastructure Safety Management also demands the ranking of high accident concentration sites. This paper gives an introduction to localizing high accident concentration sites and the indicators used by Italy and Hungary. Accident and traffic volume data are gathered for motorway sections from both countries. Safety ranking is made using two conventional indicators, absolute number of accidents and accident rate. A more sophisticated ranking using the Empirical Bayes method is applied. Expected average crash frequency with Empirical Bayes adjustment is calculated. Based on the estimation of the crash frequency, the Critical Crash Rate (CCR) was added to identify and rank black spots. This additional performance measure is able to take into account traffic volume as required by the EU Directive. Results of the Empirical Bayes method are compared with the conventional procedures. It is concluded that the results are not comparable; inasmuch as there are modifications in the order of black spots. Based on the comparison of results recommendations are given to change the practice in both countries.
The analysis of a road network could be carried out using different techniques, the most advanced... more The analysis of a road network could be carried out using different techniques, the most advanced of which for the identification of hazardous sites are based on a statistical tool known as a " Safety Performance Function " (SPF). SPFs are fundamental to procedures in the Highway Safety Manual (HSM) and Safety Analyst, both of which require calibration of the SPFs to local conditions. In the case of infrastructure in which the traffic flow is physically divided, such as motorways, there are two different methods to calibrate an SPF; one is based on a consideration of two directional segments, the other one is based on mono-directional segments with a correction factor that takes into account the presence of two directional traffic, as proposed by Safety Analyst. In the first case, traffic flows are the sum of traffic flows for each direction. The two methods give a different calibration factor for local condition, i.e., different performance in terms of goodness of fit and SPF transferability. This paper seeks to address these differences by investigating the two approaches to estimate crash count using a motorway sample data from Italy and focusing on a comparison in terms of model transferability. Furthermore two different SPFs were calibrated on the same data using the two different functional equation form, to evaluate the goodness of fit of the two different traffic based segmentation. The goodness of fit of the models is investigated using CURE plots and the R 2 values. The four sets of models give good results in terms of goodness of fit but they have different values for the calibration factor. The calibration factor of the calibrated mono-directional model is closer to a value of one, suggesting a better goodness of fit on the contrary the HSM model gives the better performance in terms of transfer ability where crash data are not available.
Road Agencies set quantitative targets and adopt related road safety strategies within the priori... more Road Agencies set quantitative targets and adopt related road safety strategies within the priorities and the available resources at the time of an economic crisis. In this framework, benefit-cost analyses (BCA) are carried out to support the decision making process and alternative measures are ranked according to their expected benefit and benefit-cost ratio calculated using a Safety Performance Function (SPF) and Crash Modification Factors (CMFs) as predictors of future safety performances. Due to the variance of CMFs and crash frequency we are uncertain what the benefits of some future actions will be. The chance of making wrong decisions depends on the size of the standard deviation of the probability distribution of the considered stochastic variables. To deal with the uncertainty inherent in the decision making process, a reliability based assessment of benefits must be performed introducing a stochastic approach. In the paper the variability of the CMFs, the predicted number of crashes and the crash costs are taken into account in a reliability based BCA to address improvements and issues of an accurate probabilistic approach when compared to the deterministic results or other approximated procedures. A case study is presented comparing different safety countermeasures selected to reduce crash frequency and severity on sharp curves in motorways. These measures include retrofitting of old safety barriers, delineation systems and shoulder rumble strips. The methodology was applied using the Monte Carlo simulations to calculate the probability of failure of BCA statements. Results and comparisons with alternative approaches, like the one proposed in the HSM, are presented showing remarkable differences in the evaluation of outcomes which can be achieved.
The lack of appropriate and timely maintenance produces increase in the cost of future treatments... more The lack of appropriate and timely maintenance produces increase in the cost of future treatments and vehicle operating costs with negative impact on environment in terms of use of natural resources, GHG emission and energy consumption. There is a need to provide recommendations for Road Asset Management leading identify and prioritize measures that effectively address Mobility, Safety and Environmental sustainability. The paper object is to augment environmental sustainability and resource efficiency issues in Road Asset Management with particular emphasis on pavement maintenance. The pavement issues which have the greatest potentialities for an environmental sustainable and resource efficient Road Asset Management, are presented in the paper.
Accident prediction models (APMs) are useful tools for estimating the expected number of crashes ... more Accident prediction models (APMs) are useful tools for estimating the expected number of crashes over a road network which are typically used in the screening of sites with promise for safety improvements. This study shows a procedure of analysis for motorways network offering a comparison between the conventional analytical techniques based on GLM (Generalized Linear Model) and a different approach based on GEE (General Estimating Equation). The GEE model, incorporating the time trend, is compared in terms of results and reliability in the estimation with conventional models (GLM) that do not take into account the temporal correlation of accident data.
Most crash prediction models are statistically-based prediction methods which require significant... more Most crash prediction models are statistically-based prediction methods which require significant efforts in crash data collection and may not be applied in particular traffic environments due to the limitation of data sources. Traffic conflict studies have been proposed to mitigate this issue using short time survey to count traffic conflicts which are assumed as a surrogate measure of safety. Unfortunately, they are again field-based studies which can be carried out after the implementation of the treatment. Nowadays, simulation tools can be utilized in traffic conflict studies. Traffic conflicts can be detected through SSAM where vehicle trajectories from micro-simulation software (e.g. VISSIM) are post-processed. In this framework the present research work deals with passing relief lanes safety performance. According to international experiences, such sections provide an improvement of traffic and safety performance in comparison to two-lane rural roads. Indeed, to achieve safety benefits, the length of a passing lane section should not be shorter than the recommended minimum value. In accordance with technical standards of different countries, those lengths vary from 0.5 km (Poland) to 1.2 km (Austria). The reasons behind the application of shorter lanes in Poland include the high density of intersections and budget constraints. Short passing sections are a cause of concerns because they can lead to hazardous maneuvers and may increase the number of conflicts in the merging area. The lack of wide implementation of short passing relief lanes does not allow the performance of a reliable traffic safety analysis due to the lack of observed data. The present research paper aims to fill this gap by performing a safety evaluation of 2+1 cross-sections with short passing relief lanes, where the discharge of platoons is distinctly reduced. The proposed models provide a simple approach in determining the boundary conditions regarding safety to determine the minimum required length of a passing relief lane.
The subgrade is the top surface of a roadbed upon which the pavement structure is constructed. Th... more The 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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Papers by Carmelo D'Agostino
Le nuove tecnologie basate sulla navigazione satellitare, inoltre, si stanno rapidamente evolvendo verso forme di assistenza anche per gli utenti non tradizionali dei navigatori satellitari, cioè i pedoni.
Sono stati infatti sviluppati sistemi di navigazione GPS che presentano funzioni sempre più orientate all’utenza pedonale.
Le funzioni privilegiate sono essenzialmente quelle di carattere turistico (per favorire il raggiungimento di luoghi di interesse storico-culturale quali monumenti, chiese, piazze, etc.), investigativo (per localizzare un obiettivo mobile durante operazioni in incognito da parte delle forze dell’ordine o di privati), lavorativo (ad es., per i corrieri che effettuano consegne nei centri pedonali). Di particolare interesse è poi la cosiddetta “funzione dell’ultimo miglio” che consente all’utente di registrare la posizione del proprio veicolo parcheggiato in modo tale da poterlo facilmente ritrovare una volta che si è di ritorno dal luogo raggiunto a piedi.
Il presente gruppo di ricerca, intende proporre un contributo verso lo sviluppo di un sistema di navigazione satellitare pedonale in cui vengano introdotte opzioni di scelta dei percorsi ottimali dal punto di vista del livello di sicurezza offerto dagli elementi componenti le infrastrutture stradali in ambito urbano. Attraverso l’approfondita caratterizzazione del livello di sicurezza garantito dai percorsi pedonali mediante opportuni indicatori prestazionali si vogliono creare i presupposti per una gestione interattiva dei flussi pedonali. In particolare, grazie al supporto dei Sistemi Informativi Territoriali integrati con la tecnologia GPS, è possibile prospettare scenari futuri in cui i pedoni siano avvisati in tempo reale in merito agli elementi della rete stradale (nodi e tronchi) in grado di offrire le migliori prestazioni in termini di sicurezza; il tutto, in coerenza con le esigenze prioritarie degli utenti, tradizionalmente espresse in funzione della lunghezza dei percorsi pedonali e dei tempi di percorrenza, e mettendo in conto anche le necessità delle categorie di utenti pedonali che manifestano condizioni di disagio aggiuntive quali gli anziani ed i disabili.
Due to the variance of CMFs and crash frequency we are uncertain what the benefits of some future actions will be. The chance of making a wrong decisions depends on the size of the standard deviation of the probability distribution of CMFs and SPF, as well.
To deal with the uncertainty inherent in the decision making process, a reliability based assessment of benefits must be performed introducing a stochastic approach. In the paper the variance of the CMFs and SPFs are taken into account in a reliability based BCA to address improvements and issues of an accurate probabilistic approach when compared to the deterministic results or other approximated procedures. A case study is presented comparing different safety countermeasures selected to reduce crash frequency and severity on sharp curves in motorway. These measures include retrofitting of old safety barrier, delineation systems, shoulder rumble strips and their combinations. The methodology was applied using Monte Carlo simulations to calculate the probability of failure of BCA statements. Results and comparisons with alternative approaches, like that proposed in the HSM, are presented showing remarkable differences in the evaluation outcomes that can be achieved.
Le nuove tecnologie basate sulla navigazione satellitare, inoltre, si stanno rapidamente evolvendo verso forme di assistenza anche per gli utenti non tradizionali dei navigatori satellitari, cioè i pedoni.
Sono stati infatti sviluppati sistemi di navigazione GPS che presentano funzioni sempre più orientate all’utenza pedonale.
Le funzioni privilegiate sono essenzialmente quelle di carattere turistico (per favorire il raggiungimento di luoghi di interesse storico-culturale quali monumenti, chiese, piazze, etc.), investigativo (per localizzare un obiettivo mobile durante operazioni in incognito da parte delle forze dell’ordine o di privati), lavorativo (ad es., per i corrieri che effettuano consegne nei centri pedonali). Di particolare interesse è poi la cosiddetta “funzione dell’ultimo miglio” che consente all’utente di registrare la posizione del proprio veicolo parcheggiato in modo tale da poterlo facilmente ritrovare una volta che si è di ritorno dal luogo raggiunto a piedi.
Il presente gruppo di ricerca, intende proporre un contributo verso lo sviluppo di un sistema di navigazione satellitare pedonale in cui vengano introdotte opzioni di scelta dei percorsi ottimali dal punto di vista del livello di sicurezza offerto dagli elementi componenti le infrastrutture stradali in ambito urbano. Attraverso l’approfondita caratterizzazione del livello di sicurezza garantito dai percorsi pedonali mediante opportuni indicatori prestazionali si vogliono creare i presupposti per una gestione interattiva dei flussi pedonali. In particolare, grazie al supporto dei Sistemi Informativi Territoriali integrati con la tecnologia GPS, è possibile prospettare scenari futuri in cui i pedoni siano avvisati in tempo reale in merito agli elementi della rete stradale (nodi e tronchi) in grado di offrire le migliori prestazioni in termini di sicurezza; il tutto, in coerenza con le esigenze prioritarie degli utenti, tradizionalmente espresse in funzione della lunghezza dei percorsi pedonali e dei tempi di percorrenza, e mettendo in conto anche le necessità delle categorie di utenti pedonali che manifestano condizioni di disagio aggiuntive quali gli anziani ed i disabili.
Due to the variance of CMFs and crash frequency we are uncertain what the benefits of some future actions will be. The chance of making a wrong decisions depends on the size of the standard deviation of the probability distribution of CMFs and SPF, as well.
To deal with the uncertainty inherent in the decision making process, a reliability based assessment of benefits must be performed introducing a stochastic approach. In the paper the variance of the CMFs and SPFs are taken into account in a reliability based BCA to address improvements and issues of an accurate probabilistic approach when compared to the deterministic results or other approximated procedures. A case study is presented comparing different safety countermeasures selected to reduce crash frequency and severity on sharp curves in motorway. These measures include retrofitting of old safety barrier, delineation systems, shoulder rumble strips and their combinations. The methodology was applied using Monte Carlo simulations to calculate the probability of failure of BCA statements. Results and comparisons with alternative approaches, like that proposed in the HSM, are presented showing remarkable differences in the evaluation outcomes that can be achieved.