María Castro

GIS-Based System for Sight Distance Analysis of Highways

Analyzing the distance visible to a driver on a highway is important for traffic safety, especially in manoeuvres such as emergency stops, when passing another vehicle, or when vehicles cross at intersections. Software that calculates highway distances visible to a driver has been developed. This software is supported by a geographic information system (GIS) and can use a trajectory defined by points obtained with a global navigation satellite system (GNSS) receiver instead of relying on project information. The software includes specific tools for studying shortcomings in three-dimensional (3D) alignment; mainly, this pertains to divings. In this article, the software and its application to a case study are presented. The results are compared with those obtained using an existing validated procedure.

Operating speed and speed differential for highway design consistency

A critical factor in highway design is maintaining a good consistency with a road geometry that fits the drivers’ expectations. Presently, highway geometric design consistency is usually evaluated on the basis of operating-speed profile analysis, which requires the use of operating-speed models. This paper presents research carried out in Colombia consisting of a study of vehicle speeds on tangents and curves of two-lane rural highways. Car speeds were measured on the approach tangent and at the beginning, middle, and end points of curves by using two radar meters. The operating-speed prediction models that were developed are described. The speed change experienced by drivers from tangent to curve was also studied, and a model is presented that predicts this change. Finally, the model developed for operating-speed prediction at the midpoint of curves was compared with equivalent models calibrated in other countries and applied to a Colombian highway. This comparative study highlights the importance of using speed-prediction models calibrated according to local conditions.

LIDAR-based roadway and roadside modelling for sight distance studies

Sight distance is a key aspect of road design and operation because of its relationship to traffic safety. The most realistic procedures for calculating the section of roadway visibility to the driver require the use of digital elevation models (DEM), which represent both the roadway itself and the features along the roadside. In this study, the influence of different types of DEM, an essential asset in sight distance analysis, is evaluated. Digital terrain models (DTMs), which represent the bare ground surface, and digital surface models (DSMs) that also consider elements above the terrain have been utilised. Both are high-resolution models obtained through airborne Light Detection and Ranging (LIDAR) or terrestrial vehicle (Mobile Mapping System, MMS). In addition, this study shows the influence of roadside vegetation on sight distance, revealing the underlying difficulties and suggesting possible solutions for sight distance studies when using these models.

Highway design software as support of a project-based learning course

Traditionally, practical training of students in highway design has been based on solving geometric problems without using professional highway design software. In a degree of the Technical University of Madrid (UPM), teaching of this subject has been redesigned using a project‐based learning approach. Along the course, the students make a complete project of a highway using professional software and procedures. The highway design software chosen includes a simulator that makes a virtual journey along the highway from the point of view of a driver traveling on it. A detailed description of the course program and the software used is provided.

Thermal Sensitivity and Fatigue Life of Gap-Graded Asphalt Mixes Incorporating Crumb Rubber from Tire Waste:

The most usual asphalt mix applied for thin overlays on Spanish roads is produced with a gap-graded combination of aggregates and a polymer-modified binder. Nevertheless, reflective cracking usually affects the overlay so that the surface of the pavement soon begins to reveal a network of cracks. The brittleness and aging of asphalt mixes at low temperatures encourage the appearance and progress of these cracks. Asphalt mixes incorporating rubber from discarded tires are believed to control reflective cracking well. This paper presents a study performed on five gap-graded asphalt mixes, three containing rubber from tire waste. Every mix was tested at two stages of aging in accordance with the laboratory-accelerated aging processes proposed by SHRP. Dynamic moduli at several temperatures, ranging from −15°C to 40°C, and the fatigue life of each mix at 20°C were measured. The results are provided to help researchers build realistic models for studying reflective cracking as a function of the actual characteristics of the materials. The results show that the tire rubber, especially when incorporated by the wet process, enhances the fatigue life of the mixes. The thermal sensitivity of the mix decreases as the content of rubber arises, regardless of whether the rubber has been incorporated by the wet or the dry process. In addition, the paper reports the difficulties with the SHRP accelerated aging processes and raises some doubts about these aging processes when applied to rubberized asphalt mixes.

Spatial analysis of geometric design consistency and road sight distance

Because of the high number of crashes occurring on highways, it is necessary to intensify the search for new tools that help in understanding their causes. This research explores the use of a geographic information system (GIS) for an integrated analysis, taking into account two accident-related factors: design consistency (DC) (based on vehicle speed) and available sight distance (ASD) (based on visibility). Both factors require specific GIS software add-ins, which are explained. Digital terrain models (DTMs), vehicle paths, road centerlines, a speed prediction model, and crash data are integrated in the GIS. The usefulness of this approach has been assessed through a study of more than 500 crashes. From a regularly spaced grid, the terrain (bare ground) has been modeled through a triangulated irregular network (TIN). The length of the roads analyzed is greater than 100 km. Results have shown that DC and ASD could be related to crashes in approximately 4% of cases. In order to illustrate the potential of GIS, two crashes are fully analyzed: a car rollover after running off road on the right side and a rear-end collision of two moving vehicles. Although this procedure uses two software add-ins that are available only for ArcGIS, the study gives a practical demonstration of the suitability of GIS for conducting integrated studies of road safety.

Reliability-based analysis of sight distance modelling for traffic safety

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, ) 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.