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[EN] The analysis of road safety is critical in road design. Complying to guidelines is not enough to ensure the highest safety levels, so many of them encourage designers to virtually recreate and test their roads, benefitting from the evolution of driving simulators in recent years. However, an accurate recreation of the road and its environment represents a real bottleneck in the process. A very important limitation lies in the diversity of input data, from different sources and requiring specific adaptations for every single simulator. This paper aims at showing a framework for recreating faster virtual scenarios by using an Industry Foundation Classes (IFC)-based file. This methodology was compared to two other conventional methods for developing driving scenarios. The main outcome of this study has demonstrated that with a data exchange file in IFC format, virtual scenarios can be faster designed to carry out safety audits with driving simulators. As a result, the editing, programming, and processing times were substantially reduced using the proposed IFC exchange file format through a BIM (Building Information Modeling) model. This methodology facilitates cost-savings, execution, and optimization resources in road safety analysis., This research was funded by the Spanish Center for Industrial Technological Development (CDTI), as well as the European Regional Development Fund, grant number EXP-00091379/ITC-20161077.

[EN] In Spain, a new challenge is emerging due to the increase of many recreational bicyclists on two-lane rural roads. These facilities have been mainly designed for motorized vehicles, so the coexistence of cyclists and drivers produces an impact, in terms of road safety and operation. In order to analyze the occurrence of crashes and enhance safety for bicycling, it is crucial to know the cycling volume. Standard procedures recommend using data from permanent stations and temporary short counts, but bicycle volumes are rarely monitored in rural roads. However, bicyclists tend to track their leisure and exercise activities with fitness apps that use GPS. In this context, this research aims at analyzing the daily and seasonal variability of the Strava Usage Rate (SUR), defined as the proportion of bicyclists using the Strava app along a certain segment on rural highways, to estimate the Annual Average Daily Bicycle (AADB) volume on rural roads. The findings of this study offer possible solutions to policy makers in terms of planning and design of the cycling network. Moreover, the use of crowdsourced data from the Strava app will potentially save costs to public agencies, since public data could replace costly counting campaigns., This research was funded by the Ministry of Science, Innovation, and Universities, grant number TRA2016-80897-R and the General Directorate of Education, Research, Culture and Sport of the Valencian Government, grant number GV/2017/038

The novel semi-autonomous vehicles are becoming a reality in our roads, being a very important technological advance with promising operational and safety improvements. However, road infrastructure must be ready to host them. The technologies of these driving automation systems require certain road conditions that are not always fulfilled, causing the systems to fail. These failures generally transfer negotiation control to drivers, which may induce a crash if they were not aware of road and traffic conditions. This research analyses how ready the road horizontal alignment is for existing semi-autonomous systems. A Level 2 vehicle has been tested on many different horizontal curves, finding a strong relationship between the maximum speed that the autonomous system can attain and the curve geometry. This maximum speed is proposed as a new concept (automated speed) and has been found to be lower than the design, operating and posted speeds in many cases. Another new concept – automated driving consistency – arises, as the difference between automated and operating speeds. The related inconsistencies can be addressed with the new concept of Level of Service for Automated Driving (LOSAD), which summarizes how ready a corridor is for a certain driving automation system. This parameter should be determined – further certified – for any homogeneous road segment, and later informed to drivers.

In the medium-term, the number of semi-autonomous vehicles is expected to rise significantly. These changes in vehicle capabilities make it necessary to analyze their interaction with road infrastructure, which has been developed for human-driven vehicles. Current systems use artificial vision, recording the oncoming road and using the center and edgeline road markings to automatically facilitate keeping the vehicle within the lane. In addition to alignment and road markings, lane width has emerged as one of the geometric parameters that might cause disengagement and therefore must be assessed. The objective of this research was to study the impact of lane width on semi-autonomous vehicle performance. The automatic lateral control of this type of vehicle was tested along 81 lanes of an urban arterial comprising diverse widths. Results showed that the semi-autonomous system tended to fail on narrow lanes. There was a maximum width below which human control was always required—referred to as the human lane width—measuring 2.5 m. A minimum width above which automatic control was always possible—the automatic lane width—was established to be 2.75 m. Finally, a lane width of 2.72 m was found to have the same probability of automatic and human lateral control, namely the critical lane width. Following a similar methodology, these parameters could be determined for other vehicles, enhancing the interaction between autonomous vehicles and road infrastructure and thus supporting rapid deployment of autonomous technology without compromising safety.

The aim of this study is to analyze the influence of horizontal geometric design and vehicle operation on fuel consumption and gas emissions produced by passenger cars. Continuous speed data were collected along 15 two-lane rural road sections. Different horizontal alignment indexes and operational variables were obtained. Fuel consumption and gas emissions were estimated by applying the VT-Micro model. The results showed that Curvature Change Rate and average speed have a significant impact on average fuel consumption and gas emissions. Finally, different regression models were calibrated based on these variables to estimate fuel consumption [l/100 km] and emissions [gr/km]. These results could be the basis to incorporate environmental sustainability principles into road design guidelines, since currently they do not take into account the environmental impact related to highway geometric design.

[EN] Road crashes are mainly caused by three concurrent factors: infrastructure, vehicle, and human factors. The interaction between the infrastructure and human factors leads to the concept of geometric design consistency. Recently, a global consistency model was developed based on the difference between the inertial operating speed profile and the operating speed profile. The first was defined as the weighted average operating speed of the previous road section based on distance, and represents drivers¿ expectancies, whereas the second represents road behavior. However, drivers¿ expectancies are related to short-term memory which declines gradually and depends on time. Thus, a time-based inertial operating speed would allow a more accurate estimation of the phenomenon. This research analyzes different periods of time and weighting distributions to identify how drivers¿ expectancies should be estimated. A set of 71 homogeneous road segments located in Italy were considered in the study. As a result, 25 seconds and a convex parabolic distribution should be used to calculate the inertial operating speed profile. This new way of estimating drivers¿ expectancies showed better results than those obtained based on distance. Finally, the proposed consistency model was compared with the previous models and was found to be able to assess more accurately the geometric design consistency. Therefore, the proposed consistency model is a useful tool for engineers to estimate the number of crashes so that they can incorporate road safety considerations into the geometric design of either new two-lane rural roads, or improving the existing ones., This research was subsidized by the Spanish Ministry of Economy, Industry, and Competitiveness through ‘‘Ayudas a la movilidad predoctoral para la realizacio´n de estancias breves en centros de I+ D 2015.’’ The study presented in this paper is also part of the research project entitled ‘‘CASEFU - Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales’’ (TRA2013-42578-P), subsidized by the Spanish Ministry of Economy, Industry, and Competitiveness and the European Social Fund. In addition, the authors would like to thank the ‘‘Azienda Nazionale Autonoma delle Strade’’ (ANAS) and the ‘‘Automobile Club Italia’’ (ACI), who provided traffic and crash data, respectively

[EN] Highway vehicles driving on rural roads account for more than 50% of all CO2 emissions produced by the transportation sector in Europe. Although the policy measures to mitigate Greenhouse Gas emissions are increasing, these do not include policies aimed at reducing emissions by means of highway geometric design, which significantly influences drivers¿ speeds and accelerations and, consequently, plays a major role on fuel consumption and emissions. Therefore, the main objective of this research is to study the influence of the geometric design consistency on vehicle CO2 emissions. To do this, continuous speed data were collected on 47 homogeneous road segments by means of Global Positioning System devices. Vehicle CO2 emissions were estimated by applying the VT-micro model, whereas geometric design consistency was assessed considering different global consistency models. As a conclusion, vehicle CO2 emissions decreases as the consistency level of a homogeneous road segment increases. Specifically, a good consistency road segment has been found to present an emission rate 20-30% lower than a poor-consistent one. Therefore, the design of consistent roads allows, in addition to maximize road safety, to help to achieve more environmentally sustainable highways, reducing CO2 emission production., The presented study is part of the research project titled “CASEFU – Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales” (TRA2013-42578-P), subsidized by the Spanish Ministryof Economy, Industry, and Competitiveness and the European Social Fund. In addition, authors would like to thank Professor Hesham A. Rakha, Virginia Tech (USA), for providing the VT-Micro model and assessing the authors in its use to obtain outcomes.

[EN] Road crash occurrence is closely related to the geometric design consistency, which can be defined as how drivers¿ expectancies and road behavior fit. To this regard, the crash rate on a road segment increases as its consistency level decreases. To assess this phenomenon, inertial consistency models were recently developed. These models are based on the difference between the inertial operating speed, which represents drivers¿ expectancies, and the operating speed, which represents road behavior. The higher the difference between both speeds, the higher the likelihood of crash occurrence. This research aims to validate and calibrate these consistency models on American two-lane rural roads. For this, a total of 194 homogeneous road segments and 977 horizontal curves along 665 km in North Carolina (US) were used. As a result, the geometric design consistency was identified as a major factor of crash occurrence. The higher the difference between drivers¿ expectancies and road behavior, the higher the crash rate. Likewise, the greater the consistency level, the greater the percentage of horizontal curves without reported crashes. A Safety Performance Function was also calibrated to estimate the number of crashes on a road segment. Consistency thresholds were defined and tested to identify where these crashes are more likely to take place. Finally, the results obtained in this study were compared with those obtained previously on Spanish highways. To this regard, the crash rate on an American highway was 1.85 times greater than those observed on a Spanish highway under the same risk exposure and consistency conditions. Therefore, different tools were developed to enhance the assessment of road safety to the geometric design of both new two-lane rural roads and improvements of existing highways., This research was subsidized by the Spanish Ministry of Economy, Industry, and Competitiveness through “Ayudas a la movilidad predoctoral para la realización de estancias breves en centros de I+D 2017” (EEBB-I-17-12154). The study presented in this paper is also part of the research project titled “CASEFU - Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales” (TRA2013-42578-P), subsidized by the Spanish Ministry of Economy, Industry, and Competitiveness and the European Social Fund. In addition, the authors would like to thank the North Carolina Department of Transportation (NCDOT), which provided traffic and crash data.

[EN] Free-flow speed variation of passenger vehicles along a road segment is one of the most used factors in road safety studies, as a surrogate measure to evaluate road design consistency. Free-flow speed may be measured when a road segment is already built but must be estimated during the design phase. Several studies have been carried out to calibrate models to estimate free-flow speed, with geometric features as explanatory variables. Currently, most free-flow speed models focus only on mean speed or speed in particular percentiles, such as the 85th or 95th. Moreover, most studies have assumed normality in the free-flow speed distribution without checking this hypothesis. The main objective of this study was to analyze the free-flow speed distribution on two-lane rural road curves and tangents. The research focused on two main issues: determining whether speed data were normally distributed at a specific site and analyzing the behavior of the mean and standard deviation of speed on curves and tangents. The study was based on continuous operating speed profiles, which were obtained from a database of more than 16,000 vehicles/km. A total of 63 horizontal curves and 78 tangents were analyzed. According to the results, the normal distribution is not the best distribution in most cases for describing free-flow speeds. In 46 of the curves and 64 of the tangents, free-flow speed cannot be assumed to be normally distributed. Therefore, some other distributions should be tested in further research., The study presented in this paper is part of the research project CASEFU-Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales, subsidized by the Spanish Ministry of Economy and Competitiveness and the European Social Fund. In addition, the authors thank the Center for Studies and Experimentation of Public Works of the Spanish Ministry of Public Works for subsidizing the field data collection, and the Infrastructure and Transportation Department of the General Directorate of Public Works of the Valencian Government, the Valencian Provincial Council, and the Ministry of the Interior, especially the General Directorate of Traffic of Spain, for their cooperation in gathering the field data.

[EN] In 2014, highway vehicles accounted for 72.8% of all Greenhouse Gases emissions from transportation in Europe. In the United States (US), emissions follow a similar trend. Although many initiatives try to mitigate emissions by focusing on traffic operations, little is known about the relationship between emissions and road design. It is feasible that some designs may increase average flow speed and reduce accelerations, consequently minimizing emissions. This study aims to evaluate the impact of road horizontal alignment on CO2 emissions produced by passenger cars using a new methodology based on naturalistic data collection. Individual continuous speed profiles were collected from actual drivers along eleven two-lane rural road sections that were divided into 29 homogeneous road segments. The CO2 emission rate for each homogeneous road segment was estimated as the average of CO2 emission rates of all vehicles driving, estimated by applying the VT-Micro model. The analysis concluded that CO2 emission rates increase with the Curvature Change Rate. Smooth road segments normally allowed drivers to reach higher speeds and maintain them with fewer accelerations. Additionally, smother segments required less time to cover the same distance, so emissions per length were lower. It was also observed that low mean speeds produce high CO2 emission rates and they increase even more on roads with high speed dispersions. Based on this data, several regression models were calibrated for different vehicle types to estimate CO2 emissions on a specific road segment. These results could be used to incorporate sustainability principles to highway geometric design., The study presented in this paper is part of the research project titled "CASEFU - Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales" (TRA2013-42578-P), subsidized by the Spanish Ministry of Economy, Industry, and Competitiveness and the European Social Fund. In addition, the authors would like to thank the Center for Studies and Experimentation of Public Works (CEDEX) of the Spanish Ministry of Public Works for subsidizing the field data collection and the General Directorate of Public Works and Transportation of the Valencian Government, to the Road Department of the Valencian Provincial Council, and to the Spanish Ministry of the Interior, especially the General Directorate of Traffic of Spain, for their cooperation in field data gathering. Finally, we would like to thank Professor Hesham A. Rakha, Virginia Tech (USA), for providing the VT-Micro model and assessing the authors in its use to obtain outcomes.

[EN] Road crashes are mainly caused by three concurrent factors: infrastructure, vehicle and human factor. The interaction between infrastructure and human factor leads to the concept of geometric design consistency, which can be defined as how driver¿s expectations and road behavior fit. This paper presents a new global consistency model based on the difference between the inertial operating speed profile (Vi) and the operating speed profile (V85). The first one is calculated as the weighted average speed of the previous road section and represents drivers¿ expectations, whereas the second one represents road behavior. A set of 71 homogeneous two-lane rural road segments located in Italy were used in the calibration of the model. As a result, a Safety Performance Function based on this new consistency model was proposed in order to estimate the number of crashes in an entire road segment. Finally, the new model was compared with previous global consistency models, concluding that the new consistency parameter better explains the phenomenon than the previous ones. Therefore, the new consistency model is a useful tool for the engineers which allows estimating the number of crashes and incorporate road safety to the geometric design of both new two-lane rural roads and improvements of existing highways., This research was subsidized by the Spanish Ministry of Economy and Competitiveness through "Ayudas a la movilidad predoctoral para la realizacion de estancias breves en centros de I+D 2015." The study presented in this paper is also part of the research project titled "CASEFU-Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales" (TRA2013-42578-P), subsidized by the Spanish Ministry of Economy and Competitiveness and the European Social Fund. In addition, the authors would like to thank the Azienda Nazionale Autonoma delle Strade (ANAS) and the Automobile Club Italia (ACI), which provided traffic and crash data, respectively.

[EN] The most important factors for road crash occurrence are infrastructure, vehicle, and human factors. In fact, infrastructure and its interaction with human factor have been thoroughly studied in recent years through geometric design consistency, which can be defined as how drivers¿ expectations and road behavior relate. Global consistency models were calibrated in the last decade to assess road safety on an entire homogeneous road segment. However, none of them include the underlying consistency phenomenon in their formulation. Recently, a new model was developed based on the difference between the inertial operating speed profile, which represents drivers¿ expectancies, and the operating speed profile, which represents road behavior. While the operating speed represents the estimated operating speed for every location along the road, the inertial operating speed aggregates for every station the operating speed effect along some distance already covered by drivers. The authors hypothesized that this `aggregation effect¿ was connected to drivers¿ expectancies, which proved to be true based on the best model fitted. However, the exact distance (or time) that should be considered to estimate the inertial operating speed still remains unknown. This paper aims to complete this model, analyzing how the inertial operating speed varies depending on different distances and periods of time. This impact is measured considering the reliability of the corresponding consistency model. The paper also covers how the inertial operating speed should be determined along the final distance or time. For this, a total of 184 homogeneous road segments along 650¿km in Spain were used., The study presented in this paper is part of the research project titled "CASEFU - Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales" (TRA2013-42578-P), subsidized by the Spanish Ministry of Economy, Industry and Competitiveness and the European Social Fund. In addition, the authors would like to thank the Department of Housing, Public Works and Spatial Planning of the Valencian Regional Government and the Traffic Department of the Spanish Government, which provided traffic and crash data, respectively.

[ES] La velocidad de operación es uno de los factores más estudiados en el análisis de la seguridad vial por su relación con la siniestralidad. En la fase de explotación es relativamente sencillo calcular la velocidad de operación a partir de datos empíricos, pero, en las fases de planeamiento y de proyecto, sólo será posible estimarla. Numerosos autores han modelizado la velocidad de operación de vehículos ligeros en curvas de carreteras convencionales considerando su velocidad mínima. Algunos a partir de observaciones en aquellos puntos de la carretera más significativos como el punto medio de la curva (velocidad mínima), otros a partir de datos continuos utilizando, por ejemplo, dispositivos GPS. La mayoría de los modelos que estiman esta velocidad se basan únicamente en el percentil 85 de la distribución o en su velocidad media. Además, la mayoría de los estudios asumen que sus datos se distribuyen según una normal sin, en muchos casos, comprobar dicha hipótesis. El objetivo de este estudio es analizar la distribución de la velocidad desarrollada por vehículos ligeros circulando en condiciones de flujo libre en curvas de carreteras convencionales. Para ello, la investigación se basa en determinar si los datos de velocidad de 63 curvas disponibles de una base de más de 16.000 vh·km se distribuyen según una normal, y en el análisis del comportamiento de la media y la desviación típica de la distribución de velocidades en curvas. Se ha concluido que la distribución normal no es la que mejor se ajusta al comportamiento de la velocidad en la mayoría de los casos., El estudio que se ha presentado es parte del proyecto de investigación “CASEFU – Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales” (TRA2013- 42578-P), subvencionado por el Ministerio de Economía y Competitividad y el Fondo Social Europeo. Asimismo, los autores quieren agradecer al Centro de Estudios y Experimentación de Obras Públicas (CEDEX) del Ministerio de Fomento por subvencionar la investigación en la que se llevó a cabo la toma de datos, a la Dirección General de Obras Públicas, Transporte y Movilidad de la Conselleria de Vivienda, Obras Públicas y Vertebración del Territorio, a la Diputación de Valencia, y al Ministerio del Interior, especialmente a la Dirección General de Tráfico, por su colaboración en la toma de datos.

[ES] Muy diversas investigaciones previas han mostrado cómo la percepción del riesgo afecta el comportamiento de los conductores. Muchas de ellas van dirigidas a observar la diferencia de percepción entre conductores experimentados y noveles, o entre el riesgo objetivo y el percibido. Mientras que el riesgo objetivo puede ser obtenido a partir de las estadísticas de siniestralidad, el riesgo percibido es más complicado de evaluar. Existen diversos métodos, yendo desde la encuesta directa hasta técnicas de rastreo de la visión.En este estudio se presenta una nueva metodología para recoger datos de Percepción Subjetiva de Riesgo (PSR) de forma quasi-naturalística. Con esta metodología, los conductores pueden indicar de forma sencilla su percepción de confort tras recorrer cada una de las curvas que compone un trazado. Posteriormente, la correlación de estos datos con la geometría de las curvas y otras variables permite derivar sencillas reglas para obtener un diseño consistente de la carretera. Igualmente, si esta metodología es válida para ser llevada a cabo en un entorno simulado, permitiría evaluar carreteras en fase de proyecto, convirtiéndose en una valiosa herramienta para los ingenieros.Un total de 28 conductores participaron en la toma de datos, recorriendo el mismo tramo de carretera en la realidad y en entorno simulado, de 32 km. En ambos casos indicaron su percepción de PSR tras cada una de las curvas aisladas. En este estudio se muestran los resultados alcanzados, tanto en el entorno real como el simulado. Igualmente, se establecen conexiones y correlaciones entre ambos métodos, mostrando bajo qué condiciones el entorno simulado arroja valores válidos., Los autores quisieran agradecer a la Universitat Politècnica de València (UPV), que financió el proyecto de investigación “CONSIM - Desarrollo de un Modelo para la Evaluación de la Consistencia del Diseño Geométrico de Carreteras Convencionales mediante Simuladores de Conducción” (PAID 05-2012). Asimismo, agradecer también al Ministerio de Economía y Competitividad y al Fondo Social Europeo, que financiaron el proyecto de investigación “CASEFU - Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales” (TRA2013-42578-P), del cual forma parte este estudio.

[EN] In recent years, the number of road-based studies using driving simulators is growing significantly. This allows evaluating controlled situations that otherwise would require disproportionate observations in time and/or cost. The Institute of Design and Manufacturing (IDF) of the Polytechnic University of Valencia (UPV) has developed, in collaboration with the Engineering Research Group Highway (GIIC) of the UPV, a low cost simulator that allows rapid implementation and effectively a new methodology for validation studies of different roads through the implementation in the simulator scenarios of existing roads. This methodology allows the development of new scenarios based on the analysis of a layers-file system. Each layer includes different information from the road, such as mapping, geometry, signaling, aerial photos, etc. The creation of the simulated scenario is very fast based on the geometric design software, making it easier to consulting firms using the system that can evaluate and audit a particular route, obtaining reliable conclusions at minimal cost, even if the road is not actually built. This paper describes the basic structure of the layers generated for developing scenarios and guidelines for the implementation thereof. Finally the application of this methodology to a case of success will be described., Authors would like to thank Polytechnic University of Valencia (UPV) that subsidizes the research project CONSIM (PAID 05-2012).

[ES] La velocidad de operación, definida como el percentil 85 de la distribución de velocidad de vehículos ligeros circulando en carreteras convencionales en condiciones de flujo libre, es una de las principales variables en la evaluación de la consistencia del diseño geométrico. De esta forma, los únicos vehículos considerados en el análisis son los vehículos ligeros, obviando la influencia de los vehículos pesados. Para la estimación de la velocidad de operación de estos vehículos el número de modelos existentes es mínimo. Por ello, el objetivo del trabajo que se presenta es el estudio experimental de la velocidad desarrollada por vehículos pesados en carreteras convencionales. El estudio no se centra únicamente en la velocidad de operación, sino en el estudio de la distribución completa de la velocidad, ya que los percentiles bajos están relacionados con el riesgo de alcance de vehículos ligeros. Se han analizado las diferentes variables que pueden influir con especial énfasis en las variables geométricas de la carretera. El estudio se ha basado en los datos obtenidos gracias a la colaboración de dos empresas, que han permitido la colocación de dispositivos GPS de 1 Hz en vehículos de su flota. Los GPS registraron de forma continua la velocidad desarrollada por los vehículos durante la realización de su ruta habitual. La influencia sobre el comportamiento de los conductores fue mínima al tratarse de un dispositivo de pequeño tamaño ubicado en el exterior del vehículo. Tras la restitución de la geometría de las carreteras objeto de estudio y el tratamiento de los datos de velocidad registrados, se analizó la influencia de las variables geométricas del trazado, especialmente en cuanto a alzado se refiere, en la velocidad. Se ha concluido que la pendiente no tiene una influencia significativa en la elección de la velocidad por parte de los conductores de vehículos pesados en curvas de carreteras convencionales, donde el principal control de la velocidad son los radios de las propias curvas., El estudio que se ha presentado es parte del proyecto de investigación “CASEFU – Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales” (TRA2013- 42578-P), subvencionado por el Ministerio de Economía y Competitividad y el Fondo Social Europeo. Asimismo, los autores quieren agradecer a las empresas SAV y SAEVI, así como la Entidad Metropolitana para el Tratamiento de Residuos en Valencia, por su colaboración totalmente desinteresada en toma de datos.

[EN] The number of road safety studies that are based on driving simulators is growing significantly. The Polytechnic University of Valencia, Spain, developed a low-cost driving simulator for the assessment, training, and rehabilitation of drivers (SE2RCO). The main objective of this research was the validation of the driving simulator so that studies about road safety and highway geometric design that considered human factors could be performed. The validation was based on continuous speed profiles collected from 28 volunteers on a 30-km-long, two-lane rural road section. The same volunteers drove through the same road section built in SE2RCO. Speed data of 79 curves and 52 tangents were selected for the analysis. Comparison of the real and simulated speeds ensured the simulator's objective validity according to average and operating speeds. Two models were developed to predict field speeds from simulated speeds. Results showed that a simulated average speed lower than approximately 90 km/h was linked to a similar real average speed. For higher simulated speeds, the average speed in the real environment was lower than the simulated one. In addition, the actual operating speed was around 5 km/h lower than the operating speed in the driving simulator. Most volunteers assessed the quality and similarity of the virtual environment compared with the real world as medium or high and assessed the driving tasks similarly, thus achieving subjective validation of the simulator., The authors thank the Polytechnic University of Valencia, which subsidized the research project CONSIM-Desarrollo de un Modelo para la Evaluacion de la Consistencia del Diseno Geometric de Carreteras Convencionales Mediante Simuladores de Conduccion. The study presented here was also part of the research project titled CASEFU-Estudio Experimental de la Funcionalidad y Seguridad de las Carreteras Convencionales, which was subsidized by the Spanish Ministry of Economy and Competitiveness and the European Social Fund.

[ES] La cantidad de estudios de seguridad vial basados en simuladores de conducción está en continuo crecimiento. En este sentido, la Universitat Politècnica de València (UPV) ha desarrollado un simulador de conducción de bajo coste: SE2RCO (Simulador para la Evaluación, Entrenamiento y Rehabilitación de Conductores). El principal objetivo de la investigación es la validación de este simulador, con el fin de desarrollar estudios relacionados con la seguridad vial y el diseño geométrico de carreteras incorporando el factor humano. Dicha validación se ha realizado a partir de la observación en campo de los perfiles continuos de velocidad desarrollados por 28 voluntarios conduciendo su propio vehículo en un tramo de carretera convencional de 30 km. Los mismos voluntarios condujeron posteriormente en el simulador de conducción ese mismo tramo de carretera reconstruido en un entorno virtual. Un total de 79 curvas y 52 rectas fueron objeto de análisis. La comparación entre las velocidades desarrolladas en la realidad y las observadas durante la simulación permitieron llevar a cabo la validez objetiva del simulador de conducción. Los resultados mostraron que la velocidad media en el simulador y en la realidad era similar cuando la velocidad simulada era inferior a 87.3 km/h. En caso de ser superior, la velocidad media en la realidad era menor que en el simulador. En cuanto a la velocidad de operación, se observó que la velocidad real era aproximadamente 5 km/h menor que la simulada. Finalmente, estos resultados estuvieron apoyados por la percepción de los conductores, ya que la mayoría de ellos evaluaron la calidad del entorno simulado y el grado de similitud entre la tarea de conducción real y simulada como medio o alto, consiguiendo de esta manera la validez subjetiva del simulador de conducción., Los autores quisieran agradecer a la Universitat Politècnica de València (UPV), que financió el proyecto de investigación “CONSIM - Desarrollo de un Modelo para la Evaluación de la Consistencia del Diseño Geométrico de Carreteras Convencionales mediante Simuladores de Conducción” (PAID 05-2012). Asimismo, agradecer también al Ministerio de Economía y Competitividad y al Fondo Social Europeo, que financiaron el proyecto de investigación “CASEFU - Estudio experimental de la funcionalidad y seguridad de las carreteras convencionales” (TRA2013-42578-P), del cual forma parte este estudio.

The occurrence of road crashes depends on several factors, with design consistency (i.e., conformance of highway geometry to drivers' expectations) being one of the most important. A new consistency model for evaluating the performance of tangent-to-curve transitions on two-lane rural roads was developed. This model was based on the inertial consistency index (ICI) defined for each transition. The ICI was calculated at the beginning point of the curve as the difference between the average operating speed on the previous 1-km road segment (inertial operating speed) and the actual operating speed at this point. For the calibration of the ICI and its thresholds, 88 road segments, which included 1,686 tangent-to-curve transitions, were studied. The relationship between those results and the crash rate associated with each transition was analyzed. The results showed that the higher the ICI was, the higher the crash rate; thus, the probability of accidents increased. Similar results were obtained from the study of the relationship between the ICI and the weighted average crash rate of the corresponding group of transitions. A graphical and statistical analysis established that road consistency might be considered good when the ICI was lower than 10 km/h, poor when the ICI was higher than 20 km/h, and fair otherwise. A validation process that considered 20 road segments was performed. The ICI values obtained were highly correlated to the number of crashes that had occurred at the analyzed transitions. Thus, the ICI and its consistency thresholds resulted in a new approach for evaluation of consistency., The authors thank the Center for Studies and Experimentation of Public Works of the Spanish Ministry of Public Works, which partially subsidized the data collection, for obtaining the empirical operating speed profiles used in the validation process. The authors also thank the General Directorate of Public Works of the Infrastructure and Transportation Department of the Valencian government, the Valencian Province Council, and the General Directorate of Traffic of the Ministry of the Interior of the Government of Spain for their cooperation in data gathering.

Methodologies based on naturalistic observation provide the most accurate data for studying drivers' behaviour. This study presents a new methodology to obtain naturalistic data related to drivers' behaviour in a road segment. It is based on the combination of using global positioning system data and drivers' questionnaires. The continuous speed profiles along a road segment and the characteristics of drivers, of their trips and the type of their vehicles can be obtained for a great amount of drivers. It has already been successfully used for several studies, such as the development of models to estimate operating speed profile in two-lane rural road segments; or the characterisation of driving styles. These operating speed models have been the key for the development of a new geometric design consistency model, allowing an easier road safety evaluation. Besides, knowledge on the human factors that influence speed choice may be useful for road safety media campaigns and education programs designers, and also for the improvement of intelligent driver assistance systems., The authors thank 'Centre for Studies and Experimentation of Public Works (CEDEX)' of the 'Spanish Ministry of Public Works' that partially subsidizes the research. We also wish to thank to the 'General Directorate of Public Works, Urban Projects and Housing' of the 'Infrastructure, Territory and Environment Department' of the 'Valencian Government', to the 'Valencian Provincial Council' and to the 'General Directorate of Traffic' of the 'Ministry of the Interior' for their cooperation in field data gathering.

[EN] To assist in the on-going effort to reduce road fatalities as much as possible, this paper presents a new methodology to evaluate road safety in both the design and redesign stages of two-lane rural highways. This methodology is based on the analysis of road geometric design consistency, a value which will be a surrogate measure of the safety level of the two-lane rural road segment. The consistency model presented in this paper is based on the consideration of continuous operating speed profiles. The models used for their construction were obtained by using an innovative GPS-data collection method that is based on continuous operating speed profiles recorded from individual drivers. This new methodology allowed the researchers to observe the actual behavior of drivers and to develop more accurate operating speed models than was previously possible with spot-speed data collection, thereby enabling a more accurate approximation to the real phenomenon and thus a better consistency measurement. Operating speed profiles were built for 33 Spanish two-lane rural road segments, and several consistency measurements based on the global and local operating speed were checked. The final consistency model takes into account not only the global dispersion of the operating speed, but also some indexes that consider both local speed decelerations and speeds over posted speeds as well. For the development of the consistency model, the crash frequency for each study site was considered, which allowed estimating the number of crashes on a road segment by means of the calculation of its geometric design consistency. Consequently, the presented consistency evaluation method is a promising innovative tool that can be used as a surrogate measure to estimate the safety of a road segment., The authors would like to thank the Center for Studies and Experimentation of Public Works (CEDEX) of the Spanish Ministry of PublicWorks for partially subsidizing this research.We also wish to thank the Infrastructure and Transportation Department of the General Directorate of Public Works of the Valencian Government, to the Valencian Provincial Council, and to the Ministry of the Interior, especially the General Directorate of Traffic of Spain, for their cooperation in field data gathering.

[EN] In the road design process, speed variation along the road segment is an important issue to consider in adapting road geometry to drivers' expectations. To achieve this objective, speed criteria are used to evaluate road consistency. Being able to estimate the operating speed in the design phase can lead to safer road alignment. With this objective, several researchers have developed operating speed models. Most of these models are based on collected spot speed data. They assume constant speed on curves and, therefore, deceleration that occurs entirely on the approach tangent. According to these assumptions, spot speed data are collected at the center of the horizontal curve and at the midpoint of the preceding tangent to obtain operating speed models. This paper presents a new methodology based on the use of Global Positioning System devices that allow continuous collecting and processing of speed data. With this new methodology, not only can new and more accurate operating speed models he developed, but cited hypotheses can also be checked. Observed speed continuous profiles allow studies that previously could not be done, especially as related to deceleration and speed variations. This study calibrated new speed models, including three for horizontal curves with a radius curve and the curvature change rate of a single curve as explanatory variables, and one for tangents that incorporates the curve speed model. Tangent-curve speed variations are evaluated, with comparison of Delta(85)V and Delta V(85), analysis of the deceleration length occurring on a curve, and development of two deceleration models., The authors thank the Center for Studies and Experimentation of Public Works of the Spanish Ministry of Public Works, which partially subsidized the research. The authors also thank the Infrastructure and Transportation Department, General Directorate of Public Works, Valencian Government, Spain; the Valencian Provincial Council; and the Ministry of the Interior, General Directorate of Traffic, Spain, for their cooperation in field data gathering.