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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 In many cases, highway inventory data held by infrastructure operators may contain inaccurate or outdated information.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. [ABSTRACT FROM AUTHOR]

One technique employed to enhance road safety involves assessing the alignment's consistency. A prevalent measure of consistency is evaluating speed variations along the alignment. A key consideration in this assessment is determining the speed upon which the road alignment should be based. This research reveals that on two-lane rural highways with low tortuosity alignments, operating speeds on horizontal curves and tangents consistently exceeded not only the design speeds but also the maximum permissible design speed for the road category. Consequently, using the design speed to assess consistency on these roads is deemed impractical, and utilizing operating speed poses challenges due to speeds exceeding the maximum permissible limit. The objectives of this paper are twofold: to explore the relationship between design consistency and safety levels on two-lane rural highways with low tortuosity alignments (which have been insufficiently covered in research) and to propose speed-control measures to limit the maximum operating speed to the maximum permissible speed. The study findings suggest that on roads with a low tortuosity alignment, operating speeds depend much more on the general characteristics of the alignment (evaluated in the operating speed models through the desired speed). Further, assessing speed consistency is feasible only with a rigorous control of the maximum operating speed (desired speed). Additionally, a specific type of speed control is recommended, achieved by limiting the curvature change rate (CCR) of the road section based on the desired speed (environmental speed), whose evaluation becomes a crucial factor. [ABSTRACT FROM AUTHOR]

Roadway departure (RwD) crashes are significant safety concerns, especially at horizontal curves. The design of these curves plays a crucial role in mitigating RwD crashes. Thus, a thorough understanding of the interaction between driver behavior, vehicle automation, and geometric design is vital. Substantive safety, which emphasizes the inherent safety in a road's design and function, serves as the foundation of our approach. Building on this, the study employs a safe system approach to investigate the performance of horizontal curves under both non-automated and partially automated conditions, using a reliability-based analysis focusing on Stopping Sight Distance as the primary driver demand. Factors including Perception-Brake Time and Take-Over Time for automated vehicles are examined. The analysis covers horizontal curves, characterized by their geometric design and crash data. Our findings highlight a shift in the performance of horizontal curves under automation, emphasizing the need to consider automation in roadway design within the safe system approach. This study demonstrates how a reliability-based analysis can guide designers in making informed decisions regarding the geometric design of horizontal curves to reduce RwD crashes. To enhance transportation safety in the era of increasing automation, ongoing exploration of the relationships between driver behavior, automation, and road design is indispensable.

Roadway departure (RwD) crashes are significant safety concerns, especially at horizontal curves. The design of these curves plays a crucial role in mitigating RwD crashes. Thus, a thorough understanding of the interaction between driver behavior, vehicle automation, and geometric design is vital. Substantive safety, which emphasizes the inherent safety in a road's design and function, serves as the foundation of our approach. Building on this, the study employs a safe system approach to investigate the performance of horizontal curves under both non-automated and partially automated conditions, using a reliability-based analysis focusing on Stopping Sight Distance as the primary driver demand. Factors including Perception-Brake Time and Take-Over Time for automated vehicles are examined. The analysis covers horizontal curves, characterized by their geometric design and crash data. Our findings highlight a shift in the performance of horizontal curves under automation, emphasizing the need to consider automation in roadway design within the safe system approach. This study demonstrates how a reliability-based analysis can guide designers in making informed decisions regarding the geometric design of horizontal curves to reduce RwD crashes. To enhance transportation safety in the era of increasing automation, ongoing exploration of the relationships between driver behavior, automation, and road design is indispensable., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

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 CO 2 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 CO 2 emission rate for each homogeneous road segment was estimated as the average of CO 2 emission rates of all vehicles driving, estimated by applying the VT-Micro model. The analysis concluded that CO 2 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 CO 2 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 CO 2 emissions on a specific road segment. These results could be used to incorporate sustainability principles to highway geometric design. [ABSTRACT FROM AUTHOR]

Highway geometric design is a part of highway planning which focused on physical form planning, so it can fulfil the highway basic function. Highway geometric design consists of horizontal alignment and vertical alignment and each of them has its own calculation. Computer technology developments can produce softwares which is able to help and simplify the calculations of both alignments and the softwares also can produce designs which visualize the calciulation into 2D images. But 2D image is not real enough to imagine the realistic form of the highway. We need 3D visualisation to imagine the realistic highway. This paper explains how the system can produce the 3D visualisation from horizontal alignment and vertical alignment calculations. First, find the highway 3D position in the 3D coordinate. 3D coordinate has three component, x, y and z axis. From horizontal alignment calculation, we get the x and y value and from vertical alignment, we get the z value. After obtaining the 3D position, then the highway design can be drawn. This software can design the highway better because it can simulate the highway wether it is comfort enough to be passed. Abstract in Bahasa Indonesia : Desain geometrik jalan merupakan bagian dari perencanaan jalan yang dititik-beratkan pada perencanaan bentuk fisik sehingga dapat memenuhi fungsi dasar dari jalan. Desain geometrik jalan terdiri dari Alinyemen Horisontal dan Alinyemen Vertikal, dan masing-masingnya memiliki perhitungan tersendiri. Dengan adanya kemajuan teknologi komputer, mampu menghasilkan program komputer yang dapat membantu dan menyederhanakan perhitungan dari masing-masing alinyemen tersebut serta menghasilkan rancangan yang sesuai dengan kaidah yang berlaku, bahkan mampu membuat visualisasi dua dimensi dari rancangan tersebut. Namun visualisasi dua dimensi dirasa kurang mampu memberi gambaran secara nyata bentuk asli dari rancangan geometrik jalan. Oleh karena itu dalam penelitian yang dilakukan ini, dikembangkan suatu perangkat lunak yang menggunakan hasil perhitungan program komputer untuk alinyemennya dan elemen-elemen tambahan untuk menghasilkan visualisasi tiga dimensi yang sesuai desain. Pertama-tama dicari posisi jalan dalam ruang 3D. Dengan hasil perhitungan alinyemen horisontal akan didapatkan posisi mendatar dari sebuah jalan dan hasil perhitungan alinyemen vertikalnya digunakan untuk mendapatkan ketinggian jalan tersebut. Setelah mendapatkan posisi 3D barulah digambar. Hasil program visualisaasi ini dapat menampakkan posisi jalan dengan lebih baik sehingga bisa digunakan untuk mensimulasi apakah perancangan pembangunan jalan tersebut nantinya nyaman untuk dilewati, belokan atau tanjakan yang dirancang tidak berbahaya, dan lain sebagainya. Kata kunci: desain geometrik jalan, visualisasi tiga dimensi, alinyemen horisontal, alinyemen vertikal.

In this paper, a geometric model for predicting locations and times where sun glare has the potential to affect drivers on roadways was developed. Existing or prospective highway alignments can be considered. The method includes appropriate geometric models of the roadway alignment, astronomical computations for the relative position of the sun in the sky, and corrections for atmospheric refraction. Novel graphical tools were introduced to indicate the results of the model, which include sets of time and location where sun glare should be expected. The hypothesis that sun glare has an effect on congestion was tested by comparing real speed data from locations and times at which the geometric model indicates the presence of sun glare with those at which it does not. Sun glare is shown to have a statistically significant impact on mean traffic speeds. [ABSTRACT FROM AUTHOR]

Abstract: Highway geometric design in mountainous areas has been a typical challenge. The combination of short horizontal curves and restricted right-of-way is a common ground for contemplating design exception in British Columbia, Canada. In practice, collision modification factors (CMFs) are advocated as quantitative measures of changes in road features on safety. However, in many situations, there are no CMFs in the literature to predict the safety impact of changing particular road features. An important example of these road features is sight distance restriction on horizontal curves. A mechanism for risk measurement has been proposed in earlier work to assist designers in comparing the safety impact of different deviations from sight distance requirements. This paper attempts to answer the questions as to whether it is possible to reduce overall risk and achieve consistency in such reduction without demanding wider right-of-way. This problem was formulated in a multi-objective optimization framework. Following this methodology, it was possible to achieve an average reduction in risk of 25% on the nine critical cross-sections. This reduction in risk was achieved without demanding wider right-of-way and without creating measurable increase in expected collision frequency due to independent re-dimensioning of different geometric elements. On theoretical grounds, this paper represents another step into the direction of developing fully probabilistic geometric design standards. On practical grounds, this paper provides an important decision mechanism that enables the efficient use of available right-of-way for new highway construction. Case studies in this paper have been applied on a major highway development in British Columba, Canada. [Copyright &y& Elsevier]

The development of highway standard design models involves various assumptions regarding design inputs and the road environment. This paper suggests an improvement to the treatment of uncertainty in design inputs by replacing the current deterministic approach with a reliability-based framework. Reliability theory deals with the propagation of quantified variability in design inputs throughout the design process. In such a framework, each design output corresponds to a theoretical probability of noncompliance to design requirements. These probabilities can be used to assess and compare the a priori safety level associated with various design scenarios. This paper proposes that such a priori safety level of standard design outputs should be consistent and close to a prespecified target level. A set of methods is proposed to determine a target value for design safety. A general framework for calibrating standard design models is presented. To demonstrate the concept, the paper presents an application of the calibration framework to the standard design model of crest vertical curves. Calibrated design charts are constructed to yield a consistent design safety level. [ABSTRACT FROM AUTHOR]

In current design guides, the minimum radii of compound horizontal curves are based on the design requirements of simple horizontal curves for each arc on flat terrain. Such a design ignores the effects of compound curvature and vertical alignment. This paper uses computer simulation software to establish the minimum radius requirements for compound curves, considering these effects. The actual lateral acceleration experienced by a vehicle negotiating a two-dimensional (2-D) simple curve is recorded as a base scenario to facilitate the analysis of a compound curve on a flat terrain or combined with vertical alignment (three-dimensional (3-D) compound curves). The vertical alignments examined include upgrades, downgrades, crest curves, and sag curves. Mathematical models for minimum radius requirements were developed for flat and 3-D compound curves. Three types of design vehicles were used. The results show that an increase in the minimum radius ranging from 5% to 26% is required to compensate for the effects of both compound curvature and vertical alignment. [ABSTRACT FROM AUTHOR]

Several studies have shown that the perception of horizontal curves can be influenced by an overlapping vertical alignment. A previous two-phase study investigated the hypothesis that a horizontal curve appears flatter when overlapping with a vertical sag curve and sharper when overlapping with a vertical crest curve. The study concluded that the hypothesis was valid. The study also developed several statistical models to estimate the perceived radius of horizontal curves in a combined alignment. This study extends the earlier work by investigating the effect of additional geometric parameters on the perception. The parameters examined include the presence of spiral curves, the length of the spirals, and the position of the vertical curve midpoint relative to the horizontal curve. It was found that (1) driver misperception of the horizontal curvature increases as the radius of the horizontal curve increases, (2) the presence of a spiral curve affects driver perception of the horizontal curvature in the case of crest combination only, (3) the length of the spiral curve has no effect on the perception whether on crest or sag combinations, and (4) while the effect of the position of the vertical curve midpoint relative to the horizontal curve is not statistically significant, it seems that the perception problem appears to diminish as the positive offsets increases. [ABSTRACT FROM AUTHOR]

Many models have been developed to evaluate the operating speeds on two-lane rural highways. However, provided information usually lacks details essential to assess their applicability at locations other than where they were developed. This paper presents a procedure to interpret raw data collected on three horizontal curve sites of different two-lane rural highway classes in Ontario. The speed observations were categorized into three vehicle classes (passenger car, light truck, and multi-axle heavy truck) and four light condition categories (day, night, and two transition periods). The minimum headway and percentile value to define the operating speed were examined, and a revision of the current practice deemed not warranted. The findings also indicated that operating speeds do not depend on the time or vehicle class. Finally, the horizontal alignment affects the operating speed, but the speeds of the two travel directions on a horizontal curve may differ even with little contribution of the vertical alignment. [ABSTRACT FROM AUTHOR]

Highway geometric design is a complex process that is closely related to human perception and behaviour. Among the human perception issues that can affect highway geometric design is the preview sight distance, which has been defined as the distance required to perceive a horizontal curve and react properly to it. Previous attempts to quantify preview sight distance included measurement on actual roads, physical modelling, and computer animation. This paper presents a computer animation experiment that was designed to examine the effects of geometric parameters and driver characteristics on preview sight distance and to statistically model preview sight distance. Statistical analysis showed that preview sight distance depends on geometric parameters such as the horizontal curve radius, use of spiral curve and its length, presence of crest vertical curve, algebraic difference of vertical grades, vertical curvature, and road delineation. On the other hand, driver characteristics were mostly found to be insignificant parameters. Finally, statistical models were developed to predict the value of preview sight distance using linear regression analysis. The models vary in simplicity and accuracy and were formulated as a function of the general alignment configuration or as a function of the exact geometric parameters.Key words: highway geometric design, sight distance, driver characteristics, three-dimensional alignment.La conception de la géométrie d'une autoroute est un processus complexe qui est relié étroitement à la perception et au comportement humain. Parmi les sujets de perception humaine qui peuvent affecter la conception de la géométrie d'une autoroute est la distance de réaction, qui est définie comme la distance requise pour percevoir une courbe horizontale et réagir en conséquence. Les essais précédents afin de quantifier la distance de réaction ont inclus des mesures sur des routes réelles, la modélisation physique et l'animation par ordinateur. Cet article présente une expérimentation avec animations par ordinateur, qui a été conçue pour examiner les effets de paramètres géométriques et de caractéristiques propres aux conducteurs sur la distance de réaction et pour modéliser statistiquement la distance de réaction. Les analyses statistiques ont montré que la distance de réaction dépend des paramètres géometriques, tels que le rayon de la courbe horizontale, l'utilisation de courbes en spirale et leur longueur, la présence d'une courbe verticale avec une crête, la différence algébrique entre des grades verticaux, la courbure verticale, et l'alignement de la route. D'autre part, il a été trouvé que les caractéristiques des conducteurs sont des paramètres non significatifs. Finalement, des modèles statistiques ont été developpés afin de prédire la valeur de la distance de réaction en utilisant une analyse de régression linéaire. Les modèles varient en termes de simplicité et de précision, et ont été formulés en fonction de la configuration de l'alignement général ou en fonction des paramètres géométriques exacts.Mots clés : conception de la géométrie d'une autoroute, distance de vue, caractéristiques des conducteurs, alignement en trois dimensions.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]