196,018 research outputs found
Raw data (Aircraft technical sheets)
No full textRaw data (Technical sheets of the aircraft categories used in the study). In this study, we are evaluating the functionality of Engineered Materials Arrestor System (EMAS) as one possible mitigation strategy to reduce the possible consequences of landing overrun accidents. In this regard, one comprehensive MATLAB® numerical code was developed in which different aircraft parameters, EMAS geometry and material properties are analyzed as the given boundary conditions. The outputs could significantly influence the airport design, operating scenarios, regulations, emergency planning and risk management techniques and safety procedures. A risk contour map overlapped on the EMAS layout is developed to calculate the percentage of risk. The contour map assigns different probability of aircraft stoppage location to related coordinates on the arrestor bed for five different arrestor bed materials consist of three low-density concretes with different crushing strengths, gravel and foam aggregate, while the material’s crushing strength and their behavior under heavy loads are the main under investigation aspects
Assessing the impact of the slopes on runway drainage capacity based on wheel/path surface adhesion conditions
No full textAircraft braking distance is dependent on the friction between the main gear tires and runway pavement surface. Pavement texture, which is divided into macrotexture and micro-texture, has a noticeable effect upon friction, especially when the surface is wet. A risk analysis framework is developed to study the effects of longitudinal and transverse slopes on the aircraft braking distance in wet runway conditions and their influences on the probability of landing overrun accidents. This framework is operating under various water-film thicknesses, Maximum Landing Weights (MLW), and touchdown speed probability distributions for an acceptable range of longitudinal/transverse slopes and pavement texture depths. A simulator code is developed that initially computes the existing water-film thickness, as the result of intense precipitation, under aircraft main gear (depend on aircraft category) and then applies this variable as one of the main inputs to the aircraft braking distance computation. According to the obtained results, longitudinal gradient does not have a significant effect on the existing water depth on the surface although it affects the flow path length. Furthermore, 1% to 1.5% transverse slope causes rapid drainage of water from the runway surface and considerably decreases the probability of runway excursion accidents
Numerical Risk Analyses of the Impact of Meteorological Conditions on Probability of Airport Runway Excursion Accidents
No full textA continuous growth in air transport industry over the recent decades increases the probability of occurrence of accidents and consequently the need of aviation risk and safety assessments. In order to assess the risks related to aircraft ground operations, all the influencing variables that can affect the safety of maneuvers should be determined. Generally, catastrophic accidents that occur inside an aerodrome are assigned to the runway incursions and excursions. Incursions are dedicated to all events happening inside the runway (e.g. existence of an obstacle or accident of two aircraft) and excursions are considered for an unsuccessful aircraft operation which leads to surpassing the designated thresholds/borders of the runway. Landing and take-off overruns, as the main excursion events, are responsible for the major recorded incidents/accidents over the past 50 years. Many variables can affect the probability of runway-related accidents such as weather conditions, aircraft braking potential, pilot’s level of experience, etc. The scope of this study is to determine weather-wise parameters that amplify the probability of excursion events. In order to quantify the probability of each type of accidents, the effect of each meteorological variables on the aircraft operation is simulated by RSARA/LRSARA© simulators, released by Aircraft Cooperative Research Program (ACRP). In this regard, specific airports with diverse characteristics (i.e.; landlocked airport, extreme annual operations, extreme runway geometries and weather conditions) are selected as case studies in the analyses. Gusts and wind forces, specifically cross-wind, turned out to be the most dominant weather-wise influencing parameters on the occurrence of runway excursions
Probability contour map of landing overrun based on aircraft braking distance computation
No full textRunway excursions have formed the biggest share of runway-related accidents compare to all possible types of airport recorded events worldwide. Out of different possible event scenarios of excursions, runway overrun, which may occur in both landing and take-off phases of flight, is the most frequent one. Therefore many studies have been conducted focusing on determination of the contributing factors which have influence on the probability of runway overrun occurrence. This probability is directly related to the difference between aircraft Landing Distance Required (LDR) and real-time braking distance. In this regard, aircraft braking distance under certain circumstances should be computed. Runway surface condition as a result of previous studies is known to be one of the most contributing factors in runway overrun accidents. Existence of different water-film thicknesses on the pavement decreases the pavement skid resistance which leads to lower friction, for instance; consequently, longer aircraft braking distance is needed and greater risk for aircrafts to overrun is expected. Skid resistance strongly depends on the complex relationship between the aircraft operating conditions and pavement surface properties. Braking distances for a selected set of aircrafts were calculated and plotted in probability distribution format. Based on the probability distribution compared to LDR for the selected set of aircrafts, the landing overrun probability contour map and safety/risk probability distribution is presented
Evacuation plan as a risk mitigation measure: Scenario-based time estimation of partial evacuation operation
No full textThis study concentrates on evacuation procedure as a risk mitigation measure for managing and coping with emergency due to flood hazard. Emergency Management has been known as an ever-growing area of academic research in the recent decades. Particularly, Emergency Planning ahead of threatening events is crucial for moving toward a resilient society. Effective implementation of Emergency Contingency Plans during the situation of real Risk Scenarios is mainly a matter of situation awareness, cooperation and collaboration of involved organizations, timely decision-making under stressful circumstances, and availability of resources. Having defined a plan for evacuation operations as a protective measure is necessary for reduction of risk consequences to exposed population. This paper presents partial evacuation time estimations related to vehicle movement time by two methods applied to a case study (San Rocco al Porto, Italy) due to flood event: Time is estimated as a result of modeling by Mesoscopic approach. Second, the “timeline of emergency response for flood evacuation” proposed by Steve Opper is used as a quick handy method to estimate vehicle movement time
Determining the Safety Level of State Roads: An Italian Case Study
No full textThis study aims to establish an effective approach for evaluating the safety performance of road infrastructure. Road safety levels are typically quantified using safety performance indicators. However, due to the stochastic nature of accidents, many safety performance indicators cannot adequately and completely describe reality. Therefore, predictive methods based on regression models are widely used. This approach also allows for the identification of latent risk conditions in the infrastructure, even in the absence of accidents. Among available approaches, the Highway Safety Manual (HSM) methodology is chosen for its synthesis of validated highway research and best practices for incorporating safety into both new design and rehabilitation. For this study, a preliminary new version of HSM is used. The application of this method, which combines a predictive model with observed accidents through an empirical Bayesian approach, requires a calibration process that is crucial to tailoring this method to the specific study context. In this research, the predictive model is calibrated for single carriageway roads with one lane per direction across the Italian national network. Following calibration, the safety indicators are evaluated. The results obtained according to different indicators are compared to show the importance of adopting this method to counteract the regression to the mean of observed crashes. In fact, the method, supported by empirical Bayesian analysis, enables the identification of high-risk sections of the road network, selecting more sections that would be neglected by traditional indicators based solely on observed crashes. Finally, a possible approach to prioritizing sites for inspection based both on the excess of crashes and the Safety Potential (SAPO) is proposed. In addition, SAPO is adjusted to local conditions to account for the specific context and the decreasing trend of accidents over the years
Simulating the Impact of Bituminous Pavement Rutting Distress on Vehicle Braking Performance During Intense Precipitation
No full textThis study focuses on the deterioration of road pavement, particularly the formation of rutting, which adversely affects vehicle braking performance, especially in wet conditions. The research aims to predict the combined effects of rutting and intense precipitation on the vehicle braking performances by using a model based on Back-Propagation Neural Network (BPNN) algorithm. The model calculates vehicle braking distances on wet bituminous pavement, during rainfall with variable intensity, coupled with the effect of rutting, considering the presence of various Water Film Thicknesses (WFTs) over the pavement. It addresses real-world scenarios, incorporating factors like precipitation intensity, lane characteristics, rutting depths, and accumulated WFT. It can be seen that the effect of rutting on vehicle performance, particularly during rainy days when the rutting depressions are filled with rainwater, results in longer braking distances compared to dry conditions. The model’s applicability is demonstrated through validations, examining its performance against existing methods. Additionally, the developed model is verified by simulating a vehicle’s performance in a real case study, considering varying rutting depths every 10 m during intense precipitation
A Novel Methodology for Planning Urban Road Safety Interventions
No full textImproving road safety is a major challenge for urban administrations due to the high frequency of accidents and their associated social costs. This study presents a methodology that combines historical accident data analysis with a proactive risk assessment approach to enhance decision-making in road safety planning. Using the International Road Assessment Programme (iRAP) and Geographic Information Systems (GIS), the proposed framework identifies high-risk locations and estimates the benefits of planned safety interventions. A key innovation of this methodology is the integration of cost–benefit analysis to prioritize interventions, ensuring optimal resource allocation. The approach was tested in a medium-sized Italian city where it helped identify critical areas and assess the potential impact of various safety measures, such as intersection redesign and traffic-calming strategies. The results demonstrated a significant potential to reduce accidents and associated social costs, offering a scalable model for urban road safety planning. By integrating data-driven insights with proactive evaluation, this methodology supports urban administrations in implementing effective, targeted interventions that contribute to Vision Zero goals
Sensitivity analysis of the calibration factor resulting from the application of the HSM predictive method to Italian rural two-lane, two-way roads. The Emilia-Romagna case study
No full textThe present study investigates the adoption of predictive methods for road safety in the Italian context. The main goal of predictive methods is to describe safety performances of a road infrastructure according to the real number of occurred crashes and the actual infrastructure characteristics. Currently, the most reliable and widely used model is reported in the Highway Safety Manual (HSM), initially developed for the United States. In order to adapt the HSM existing model to the Italian context a calibration procedure is required. The main purpose of this study is to conduct the sensitivity analysis of the calibration factor, to evaluate the influence of various road characteristics (expressed in terms of Crash Modification Factors – CMFs) on the reliability of the model. Results show that the most influential factors are represented by planimetric curve radius, followed by shoulder type and width and Roadside Hazard Rating (RHR). In addition, the Italian roads taken into account for the present case study, which are single carriageway rural roads located in Emilia Romagna region, have generally exhibited more critical conditions compared to American roads. As a consequence, CMFs expressing the aforementioned infrastructure characteristics are typically greater than 1. Furthermore, road features and driving habits vary significantly with the orographic context (mountain, hill, or valley) and geographical area, factors that cannot be neglected when calibrating predictive models. As a result, a layered calibration would bring to the most reliable solution and, in specific situations, alternative predictive models to HSM could be developed
Evaluating the interaction between engineered materials and aircraft tyres as arresting systems in landing overrun events
No full textAccording to the registered databases of air accidents around the world, landing overruns are the most probable accidents among all runway excursion events. Although new aircraft are enhanced with the latest technologies that improve the maneuvers safety, the frequency of landing overruns are bound to increase because of the ascending growth rate of annual traffic. The principal scope of this paper is to evaluate the functionality of Engineered Materials Arresting System (EMAS) as a mitigation strategy to reduce the possible consequences of landing overrun events and in particular to determine if installing an EMAS can help land-locked airports to meet Federal Aviation Administration (FAA) recommendations in order to upgrade their Runway End Safety Areas (RESAs). In the previous studies, not enough investigations are dedicated to predicting the behavior of the aircraft and its deceleration rate after interfering EMAS and how different materials as arrestor beds would modify aircraft braking distance in RESA. Therefore, secondary objective of this paper is to determine the most optimum height of EMAS slabs, in function of execution costs and accident severity reduction rate. In this regard, a MATLAB®-based numerical code, which simulate the tire-pavement interface, is developed in order to evaluate the functionality of EMAS for aircraft ground maneuvers. Although this code is developed for both dry and wet runway conditions, dry runway's surface is selected as the boundary condition of this study. It simulates aircraft arresting distance by calculating a dynamic skid resistance between aircraft main gear and runway pavement with a fix time step. The results are plotted as risk contour intervals on the layout of EMAS that is installed at the RESA. In addition, this numerical code is adopted in order to perform a sensitivity analysis on five arresting bed materials, which consist of three low-density concretes with maximum crushing stress thresholds of 172500, 345000 and 930000 Pa, one gravel-based material and one foam aggregate-based mixture. Among all, low-density concrete with the highest crushing strength causes shorter aircraft arresting distance
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