Departament of building structures and physics

Sight distance is key to ensure safe road geometric design under all circumstances. Road design standards propose models simulating nighttime driving that contemplate the features of vehicle frontlighting systems to address the design of sag curves. These models are based on a deterministic approach, which is known to present a number of drawbacks. It neglects the stochastic nature of the variables involved and, therefore, no information is available about the safety margin of the design output. As opposed to design based on deterministic methods, probabilistic methods overcome these inconveniences providing a solid approach to broach the analysis of sag curves. This research study applied a probabilistic approach to evaluate the risk level (probability of noncompliance, P nc) associated to sag curve designs, and assessed the effect of the variables involved in headlight sight distance (HSD) on the P nc. The required stopping sight distance was considered not to be met when it exceeded the HSD. A total of 71,334 case studies were generated by combining the range of values of the variables involved in the HSD as per the Spanish geometric design standard. The risk level associated to each case was calculated by means of a Monte Carlo simulation. The results showed that variables modeling headlight features significantly affect the risk level. Moreover, the risk associated to design outputs that are considered equivalent by the standard varies significantly. Therefore, the use reliability theory in the development of standards and design guides is recommended.

Sight distance is a fundamental factor in the design of highways as it determines their operational and safety performance, particularly in nighttime. Vehicles are increasingly being equipped with driving assistance systems such as adaptive frontlighting systems, from which potential safety benefits can be derived. One of the main capabilities of adaptive headlights is controlling headlamp swiveling when driving on horizontal curves to light up a greater section of the roadway ahead. In this study, the vehicle headlight beam was recreated to simulate swiveling systems that adapt the headlight beam to the highway geometry. Diverse horizontal spread angle values were assumed for the headlight lighting pattern. Based on horizontal curvature, a total of 24,663 mathematical functions that control the headlight swiveling angle were simulated. Next, headlight sight distance (HSD) was estimated on a 3D virtual model of an in-service highway, under assumptions of fixed and swiveling headlamps. Two types of algorithms were proposed for the swiveling headlights, one based on the trajectory curvature and another one predictive. The sets of HSD results were then analyzed and compared, the effects of the swiveling headlights on HSD being quantified along the highway section studied. In addition, the performance of diverse swiveling headlights was analyzed under different 3D highway alignment combinations. Finally, the robustness of the proposed procedure was validated.

When it comes to the safe design and operation of highways, sight distance is of utmost importance. The estimation of sight distance must be performed taking the three-dimensional (3D) nature of roadways and related features into account. Horizontal curves and crest vertical curves were the common sight restrictions considered in highway design. However, overhanging features may also affect sight distance. This paper presents a 3D virtual model for evaluating sight distance on sites where overpass structures restrict sight distance and for detecting sight-distance-related issues. The procedure and inputs for the computation of sight distance are described as are the results, which were validated and applied to a case study of an in-service highway underpass. Stopping sight distance and passing sight distance were evaluated for a section of highway with specific sight-distance characteristics of overpasses. The effect of the observer and target heights on sight distance for underpasses proved the opposite of those on horizontal curves and crests. Near an overpass, the heights should be switched from those used on curves and crests to evaluate stopping and passing sight distance according to operational and safety criteria. Finally, the currently existing passing zones were evaluated by means of the results obtained, revealing possible deficiencies in the establishment of passing zones.

Sight distance is of the utmost importance for traffic safety. The consideration of three-dimensional (3D) available sight distance (ASD) in geometric design has been supported by several researchers. However, existing ASD estimation methods are two-dimensional (2D) in nature, which do not evaluate varying visibility conditions. This paper compares different methodologies of modelling the ASD. The ASD of 402 horizontal curves, located in twelve in-service two-lane rural highways, was analyzed. Three ASD estimation methods were used which include a 2D method and two different 3D methods. The ASD results obtained through 2D and 3D methodologies are compared. Also, the different conditions of the existing roadside features or geometric elements, under which the 3D ASD estimation is important, were identified. Next, reliability theory is utilized to evaluate the risk level (probability of noncompliance, nc) associated with limited sight distance for each ASD modelling method. The results of the comparison emphasized the importance of considering the 3D modelled sight distance when evaluating the associated risk either in highway design or during the service life. In addition, the results indicated that the ASD modelling approach can have a significant impact on the estimation of the safety of highway design.

As one of the main elements of geometric design, sight distance must be considered carefully for the safe and efficient operation of highways. An application developed on geographic information systems (GIS) was conceived for the three-dimensional estimation of sight distance on highways, as opposed to con-ventional two-dimensional techniques, which may underestimate or overestimate the actual visibility condi-tions. It is capable of computing the available sight distance of a highway section given the driver’s eye height, the target height, the vehicle path and an elevation model. The outcome can be studied in detail with the aid of the tools and capabilities developed, including sight-distance graphs. The influence of the input fea-tures, such as the nature of the elevation model, its resolution and the spacing between path stations on the re-sults accuracy was analyzed. The interpretation of results is also essential to explain sight distance deficien-cies and provide insight into the effect of roadside elements on those results. In addition, the sight-distance graph permits the detection and characterization of sight-hidden dips, an undesirable shortcoming in the spa-tial alignment of highways. The versatility of GIS enables, moreover, an integrated research of highway safe-ty. It allows the incorporation of diverse operational factors such as accident data, traffic volume, operating speed and design consistency to detect and diagnose potentially hazardous spots or, eventually, identify the factors involved in a particular accident. This paper describes the methodology utilized and reviews the main issues through case study examples.

Introduction: Highway safety performance at night has received less attention in research than daytime, despite the higher accident rates occurring under night-time conditions. This study presents a procedure to assess the potential hazard for drivers created by headlight glare and its interaction with the geometric design of highways. Method: The proposed procedure consists of a line-of-sight analysis performed by a geoprocessing model in geographic information systems to determine whether the rays of light that connect headlights and oncoming drivers are obstructed by either the roadway or its roadsides. Then, the procedure checks whether the non- obstructed rays of light are enclosed by a given headlight beam. Different hypotheses were set concerning the headlight beam features, including the horizontal spread angle and whether the headlights are fixed or swiveling. A highway section was selected to test and validate the procedure proposed. A 3D recreation of the highway and its environment derived from a LiDAR point cloud was used for this purpose. Results: The findings disclose how glare is produced on tangents, horizontal curves, transitions between them and sequences of curves. The effect of visual obstructions conveniently placed is also discussed. Conclusions: A greater glare incidence is produced as the horizontal headlights spread angle increases. Swiveling headlights increase glare on highways left curves and reduce it on right curves. Practical Applications: The procedure and conclusions of this study can contribute to develop more effective glare avoidance technologies as well as identify and assess glare-prone sections. The glare evaluation assists in evaluating glare countermeasures such as deciding whether to place a vegetation barrier and where.

This paper presents a practical procedure using a completely new index to determine whether a sight-hidden dip (SHD), a common shortcoming in vertical alignment, is critical for traffic safety. This sort of hidden section could be a hazard for drivers since head-on crashes may occur during passing manoeuvres. Software which estimates sight distance and is based on geographic information systems was utilised to assess real cases of SHDs, according to the German guidelines for visualisation of highways. Also, a previously existing analytical method was used to perform the same analysis and the results were compared. Moreover, the index proposed to evaluate SHDs was applied to each case to obtain a threshold value that enables discernment between critical and non-critical sections using a maximum-likelihood criterion. The method was tested using 23 real cases where the reliability of the index was proved. Finally, recommendations to avoid SHDs are provided.

Safety in highway geometric design is one of the main goals to be achieved. However, deterministic design criteria do not provide information concerning the risk associated with the design outputs proposed. To yield consistent safety levels, the sag vertical curve design model on undivided highways was calibrated using a reliability-based framework, which allows to incorporate the uncertainty associated with the model variables. The sag curve design model contemplates the features of vehicle frontlighting systems to compute the headlight sight distance (HSD), which must be equal to or greater than the stopping sight distance (SSD). A dataset of 34,238 case studies was generated. Each case study was associated with two values of the risk level, designated as probability of noncompliance (Pnc), one per driving direction. A Monte Carlo simulation was selected to calculate the values of Pnc. Through a series of interpolating surfaces of the cloud of points, contour graphs and calibrated charts were depicted. The paper provides a new methodology to verify, design and compare sag vertical curve, evaluating the risk level with the Pnc.

Safety barriers limit the severe consequences to occupants of vehicles leaving the roadway from colliding with obstacles, yet they may significantly reduce the available sight distance (ASD). A procedure was devised to accurately recreate highway guardrails in three dimensions (3D), fitting the barriers onto the curve roadsides. The effect of these devices on the reduction of the ASD was thus evaluated in a set of case studies comprising different curve radii overlapped with different vertical alignments and combined each with two safety barriers in two-lane rural roads. The 3D models of highway curves with the selected guardrails were created in a Geographic Information System. Then, a geoprocessing model was used to compute the ASD. The results made possible to quantify the ASD reduction produced by the barrier with higher containment level in relation to the highway design parameters, which can assist authorities in developing more comprehensive safety device standards.

The COVID-19 pandemic situation in 2020 forced educational institutions worldwide to fully adopt online learning for both teaching and assessment. However, this change may lead to less satisfactory learning outcomes, if the online technologies used have not been adequately applied. This study compares student engagement and performance through online continuous assessment in a one-semester structural analysis course for undergraduate architecture students before and after the pandemic outbreak. Online continuous assessment assignments had already been deployed and validated in the course evaluation system before the outbreak, and they were further leveraged during the online course. These assignments consisted of three weekly Moodle questionnaires throughout each of the fifteen course weeks, which determined the continuous assessment score. More than 200 students participated in each period. The results showed that shifting to online education affected continuous assessment outcomes very little in terms of participation rates and student performance. The possible underlying causes for the slight differences found between the two academic years are also discussed. The results highlight the robustness of the continuous assessment method used and emphasize the importance of having developed and validated online learning procedures to broach learning activities if contingency situations are required.

The mobility restrictions due to the covid-19 pandemic have created an unprecedented situation in the road system. Declared lockdowns have significantly altered the traffic volumes and perhaps also driver behavior. This study conducts research on crashes occurred on motorway A29 in Portugal before and during the disrupted mobility context. Safety performance functions were adjusted with negative binomial distribution. The segmentation was based on horizontal alignments. 5 of the 27 variables initially considered were found to be significant; namely traffic volume, segment length, curvature change rate, presence of deceleration
lane and year. The quality of the fitted models was verified using cumulative residuals plots. The results showed that a traditional statistical modelling approach explains accident occurrence in a similar way before and during the pandemic.

Structures must provide strength, stability, and stiffness to buildings and at the same time be efficient. This study addressed the effect of design elements and parameters on the strength of bolted lateral connections in steel beams under bending using the component-based finite element
method. The variables evaluated were plate thickness, horizontal and vertical spacing between bolts, and geometric arrangement of bolts. Finite element software was used to evaluate the stress state of the junction plate, its plastic deformation, and bolt shear. A sensitivity analysis was performed to determine which bolt arrangements result in safer and more efficient designs using the same components. Stress distribution within the junction plate and plastic deformation values were used to evaluate the structural performance of the joints according to EuroCode 3. The results showed that placing bolts near the edge of a plate affected the bolts’ utilization, especially with thinner plates. Additionally, introducing an offset between central and outer bolt rows is not recommended as it
worsened the stress distribution and the structural performance.

The safe and efficient operation of highways minimizes the environmental impact, reduces accidents, and promotes the reliability of the transportation infrastructure, all in support of sustainable transportation. The horizontal alignment of highways holds particular importance as it directly impacts driver behavior, vehicle stability, and overall road safety. In many cases, highway inventory data held by infrastructure operators may contain inaccurate or outdated information. The accuracy of the variables used in crash prediction models eliminates possible bias in the variable estimators. This research proposes a methodology to obtain accurate horizontal geometric features from digital imagery based on the analysis of the planimetry, feature geolocation and centerline azimuth sequence. The reliability of the method is verified by means of numerical and statistical procedures. This methodology is applied to 150 km of motorway segments in Portugal. Although it is found that the geometric characteristics of most of the inventory segments closely matched the extracted alignments, very significant differences are found in some sections. The results of the proposed procedure are illustrated with several examples. Finally, the propagation of error in the determination of the geometric design independent variables in the fitting of the statistical models is discussed based on the results.

Resumen La inspección periódica de puentes y viaductos es una actividad fundamental para evaluar la seguridad estructural, la durabilidad y la funcionalidad de estas infraestructuras. Con el paso del tiempo, pueden aumentar las exigencias de uso y, junto con la acción de los agentes meteorológicos o las operaciones de vialidad invernal, aceleran el deterioro de estas infraestructuras. En los últimos años, el uso de sistemas aéreos no tripulados, conocidos popularmente como drones, ha aparecido como una potente herramienta para complementar y posiblemente sustituir paulatinamente los métodos tradicionales. Con ello se impulsa un cambio hacia modelos de gestión más proactivos, que combinan el diagnóstico temprano con tecnologías avanzadas, permitiendo una evaluación más rápida, detallada y eficaz. En esta conferencia se abordan las aplicaciones actuales de los drones en la inspección estructural de puentes, las últimas tecnologías en sensores para la toma de datos, creación de modelos y análisis, sus ventajas y desafíos. Además, se expone el marco normativo y técnico que regula el uso de drones en la inspección de puentes y viaductos. Se muestran las oportunidades profesionales que esta tecnología ofrece en el ámbito de la ingeniería de estructuras, con una creciente demanda de perfiles técnicos capaces de integrar la inspección estructural con el análisis digital y la innovación tecnológica.