Geometric Design

Estimations of average crash density as a function of traffic elements and characteristics can be used for making good decisions relating to planning, designing, operating, and maintaining roadway networks. This study describes the relationships between total, collision, turnover, and runover accident densities with factors such as hourly traffic flow and average spot speed on multilane rural highways in Iraq. The study is based on data collected from two sources: police stations and traffic surveys. Three highways are selected in Wassit governorate as a case study to cover the studied locations of the accidents. Three highways are selected in Wassit governorate as a case study to cover the studied locations of the accidents. The selection includes Kut-Suwera, Kut-ShekhSaad, and Kut-Hay multilane divided highways located in the south of Iraq. The preliminary presentation of the studied highways was performed using Geographic Information System (GIS) software. Data collection was done to obtain crash numbers and types over five years with their locations, hourly traffic flow, and average spot speed and define roadway segments lengths of crash locations. The cumulative speed distribution curves introduce that the spot speed spectrum for each highway's whole traffic extends over a relatively wide range, indicating a maximum speed of 180 kph and a minimum speed of 30 kph. Multiple linear regression analysis is applied to the data using SPSS software to attain the relationships between the dependent variables and the independent variables to identify elements strongly correlated with crash densities. Four regression models are developed which verify good and strong statistical relationships between crash densities with the studied factors. The results show that traffic volume and driving speed have a significant impact on the crash densities. It means that there is a positive correlation between the single factors and crash occurrence. The higher volumes and the faster the driving speed, the more likely it is to crash. As the hourly traffic flow of automobile grows, the need for safe traffic facilities also extended.

This research investigates the utilization of human driving models in autonomous vehicles, particularly in scenarios with minimal or no interactions with other vehicles. Human driving models provide valuable insights into driver behavior and play a crucial role in shaping the behavior of autonomous vehicles, enhancing their performance and user experience. The primary focus of this study is the creation of a planning model for autonomous vehicles when navigating roundabouts in the absence of traffic. This model seeks to emulate human driving behavior, ensuring predictability, safety, the optimization of traffic flow, and adaptation to various roundabout geometries. To achieve this, the research introduces a trajectory model that takes into account geometric attributes and speed variations within roundabouts. The model is calibrated using empirical data and generalizes parameters through statistical regression methodologies. In particular, speed profile modeling is evaluated for its ...

It is now known that roundabouts offer high levels of safety, but different researches on this type of intersection show that several factors influence the driver's behavior, causing occasionally wrong driving behaviors that can degenerate into accidents. Understanding driver's preferences is an important goal in order to encourage an efficient and safe road design. This study aims to understand user's preferences on the geometrical-functional characteristics of roundabouts, and to associate these preferences with specific driver features. For this purpose, a stated preference survey was carried out. The declared preferences were collected through face-to-face interviews. Collected data were then processed by applying the correspondence analysis (CA). This research revealed that drivers' preferences are different depending on the type of driving behavior exhibited by drivers and, only in a less obvious manner, according to gender. Drivers with exemplary driving behavior prefer design elements that ensure a greater safety. Men with wrong driving behavior prefer roundabout configurations that are less safe but that ensure fast trajectories. Drivers with acceptable driving behavior expressed preferences that are specifically geared towards specific geometric/functional configurations of the roundabouts. The results of this work represent practical implications for a correct and safe design of road roundabouts.

More than one accident of three that involve pedestrians in urban area occurs at road intersections. The users’ inproper behaviour, the geometrical characteristics of the intersections, and the high speeds of vehicles are the main causes of pedestrian accidents. In this field, the procedures of road safety analysis (Road Safety Audit and Road Safety Review) play a fundamental role: they are the techniques of investigation aimed at identifying the safety issues and the possible improvements. Nowadays, however, the safety analysis does not allow a quantitative assessment of the level of safety regarding pedestrians. The objective of this work, is to propose a procedure for the quantitative risk analysis. The first phase of the study has been oriented to the definition of the virtual schemes associated with the possible configurations for unsignalized intersections in urban areas, predominantly characterized by local roads. The urban areas in which the residential function prevails, wh...

The issue of traffic congestion at signalized intersections is a concern in transportation systems due to the growth of urban areas and increased vehicular transportation. To study the evolution of congestion and evaluate the traffic performance operation of signalized intersections under problematic congested and improved conditions, the microscopic simulation VISSIM software is utilized. The objectives of this paper are to evaluate operational techniques, build a simulation model, and produce a well-calibrated and validated model. The methodology procedure to evaluate the signalized intersection involves the application of a traffic simulation model to observe real-time delays and stopped vehicles. Using the VISSIM software Version 9 to create an intersection model and redesign geometry with an exclusive right turn to enhance the intersection functionality and reduce delay. Our research focused on the Al-Nakhala signalized intersection located in the southern part of Palestine urban street in Baghdad city. This intersection is one of the busiest along the corridor due to significant land-use changes in the study area, including residential, educational, or commercial areas generating daily pressure from additional trips and saturating the absorptive capacity of the intersections. The proposed scenario of an exclusive rightturn could reduce the queue length and vehicle delay at the signalized intersection, resulting in a more efficient traffic operation. As a result of the reduction in vehicle delay, the Level of service (LOS) for the north, west, and east approaches improved from F to D. However, there was only a slight improvement for the south approach, with the LOS changing from E to F. Nonetheless, there was a noticeable reduction in queue length and vehicle delay ranging from 25% to 50%.

This study is concerned with assessing the effect of geometric design and land use on roundabouts, which are one of the most widely used traffic calming techniques. It aims to study the speed profiles before, at, and after thirty selected roundabouts in Jordan to develop models for predicting the circulating speed for through movement as a function of the land use of the roundabout, the roundabout geometric characteristics, and the approaching highway free-flow speed. A laser radar gun was used to capture speed data, and geometric characteristics were extracted from video pictures. Various parameters were employed to simulate the circulating speed, including the roundabout diameters, free flow speed, entry deviation angle, approaching highway exit width, circulating roadway width, and entry width. Speed profiles were developed for six roundabout types with different land uses and geometric characteristics. It was found that the roundabout effect on speed reduction extends to 150 m downstream the exit and upstream the entry. It was also discovered that the rate of reduction varies according to the upstream street free flow speed (FFS), with dramatic decreases observed at the last 50 m upstream of the entry. Variability in the speed values around the midpoint of the circulatory roadway was observed, with speed at the exit being higher than that at the entry.

Various strategies exist to choose the best intersection design considering the operational performance of an intersection. There are model-based strategies which for example choose the design with the minimal average delay or rule-based strategies which choose the design based on the total volume or specific safety preferences. These strategies choose the design for a local situation. The analysis of network effects (e.g. the total travel time in the network) of these strategies is an unexplored area of research. This paper provides some first insights in the network effects of various local intersection design strategies in comparison with a global network optimization. Strategies, advising all-way stop-controlled, two-way stop-controlled and signalized intersections and roundabouts are tested on the well-known Sioux Falls network. Results show substantial differences between the network performances and solutions of the different strategies, providing a base for future improvemen...

We present techniques for creating an approximate implicit representation of space curves and of surfaces of revolution. In both cases, the proposed techniques reduce the problem to that of implicitization of planar curves. For space curves, which are described as the intersection of two implicitly defined surfaces, we show how to generate an approximately orthogonalized implicit representation. In the case of surfaces of revolution, we address the problem of avoiding unwanted branches and singular points in the region of interest.

The contents of this analysis has been presented under the title "Open BIM für Infrastrukturmit OKSTRA und IFC-Alignment zur internationalen Standardisierung des Datenaustauschs" as part of 6th OKSTRA-Symposium (May 20th -21th 2015) in Cologne (Germany).

This paper presents an investigation into the motorists' voluntary yielding behavior to bicycles and pedestrians at uncontrolled mid-block crosswalk locations. Two study sites in the state of Montana with LED rectangular rapid flashing beacons (RRFB) warning devices were used in this investigation. Video records were acquired at the two study sites and video data was reduced to investigate the motorist's voluntary yielding of right of way to pedestrians and bicycles as they approach the crosswalks. The study found that the motorists' voluntary yielding increased with the activation of the RRFB devices at the two study sites. This finding is very consistent with the few recent studies that reported increase in the overall yielding behavior associated with the use of those devices. The study also found that the waiting position of crosswalk user(s), the presence of children and elderly, the number of crosswalk users and peak periods are all important factors that affect the voluntary yielding behavior of motorists. Study results suggest that the visibility of crosswalk users by motorists is very important consideration in the selection of crosswalk location. Further, the study recommends the push-button RRFB devices be located as close as practically possible to the roadway for increased device activation and motorists' voluntary yielding.

Amtrak has undertaken two tests of improved spiral geometry developed by the author. The first test was quite successful. The second test was less successful because of a problem in tamper operation that is unrelated to spiral geometry but was valuable because it brought that problem to light. The work reported here is based on about 5.5 years worth of geometric information for the tracks traversed by the Acela trains that Amtrak has been gathering on a semi-monthly basis for a number of years. It focuses on change with time of RMS values of line and surface roughness in and close to spiral transition curves. The work was undertaken with two goals. One goal was to determine whether or not costs incurred by Amtrak to maintain track geometry would be reduced if Amtrak adopted improved spiral geometry more generally. The answer to this question is shown to be no. The other goal was to see the results of the two tests of improved spiral geometry in a broader context and to better understand the difficulty in the second test. The cause of that difficulty is explained and is interesting. Independent of the foregoing matters, the study can assist in general understanding of geometric behavior over time of ballasted track as maintained by Amtrak.

A strongly polynomial algorithm is developed for finding an integer-valued feasible st-flow of given flow-amount which is decreasingly minimal on a specified subset F of edges in the sense that the largest flow-value on F is as small as possible, within this, the second largest flowvalue on F is as small as possible, within this, the third largest flow-value on F is as small as possible, and so on. A characterization of the set of these st-flows gives rise to an algorithm to compute a cheapest F-decreasingly minimal integer-valued feasible st-flow of given flow-amount. Decreasing minimality is a possible formal way to capture the intuitive notion of fairness.

This paper investigates potential Stopping Sight Distance (SSD) violation for 130km/h vehicle speed, on the passing lane of left curved, divided highways overlapped with crest vertical curves. The authors previously developed a SSD control methodology that relates concurrently the 3D configuration of a roadway to the dynamics of a vehicle moving along the actual roadway path, which is applied for the assessment of critical design parameters directly related to both demanded and available SSD values. Initially, by utilizing control geometric and driver - obstacle values adopted by American Association of State Highway and Transportation Officials (AASHTO) 2011 design policy, excessive SSD inadequacy areas were revealed. Subsequently, on the basis of a classic statistical and explanatory modeling approach for a number of geometry parameters, an evaluation of SSD sufficiency was carried out in terms of both the probability of SSD inadequacy and the prediction of the object height in or...

The adopted 2-D Stopping Sight Distance (SSD) adequacy investigation in current design practice may lead to design deficiencies due to inaccurate calculation of the available sight distance. Although this concern has been identified by many research studies in the past, none of those suggested a comprehensive methodology to simulate from a 3-D perspective concurrently both the cross-section design and the vehicle dynamics in space during emergency braking conditions. The proposed methodology can accurately perform SSD adequacy investigation in any 3-D road environment where the ground, road and roadside elements are inserted by identifying areas of interrupted vision lines between driverobstacle being less than the required distance necessary to bring the vehicle to a stop condition. The precision of the available SSD definition is a function of the selected incremental distance (calculation step) between two sequential points. The present approach provides flexibility among every road design and/or vehicle dynamic parameter inserted (e.g. lateral positioning and height of both driver and obstacle, vehicle speed and braking friction variations), as well as direct overview regarding design elements that restrict the driver's vision and create SSD inadequacies. As a result, precious guidance is provided to the designer for further alignment improvement but mostly an accurate aid to implement geometric design control criteria with respect to both existing as well as new road sections is delivered. The efficiency of the proposed methodology is demonstrated on a specific case study. The used software herein is part of "H12" road design software, developed at the National Technical University of Athens (NTUA).

Traditional surveying tasks (i.e. mapping of road surfaces for constructing the as-built layout) or new promising applications (i.e. paver guidance), requiring high geometric element accuracy, could well be served by dynamic positioning techniques. They can provide the basic data for constructing the bearing diagram (change of bearing along the road sections) to determine the geometric elements (i.e. the radius of

Proc. IV International Symposium Turkish-German Joint Geodetic Days, Berlin, 3-6 April. ... A COST-EFFECTIVE ROAD SURVEYING METHOD FOR THE ASSESSMENT OF ROAD ALIGNMENTS ... Basil Psarianos 1 , Demetre Paradisis 2 , Byron. Nakos 3 and George. Karras 4

The connected vehicles are the future of transportation. Road can be much safer when vehicles are able to communicate about the traffic and road conditions to its surrounding vehicles or if they can "talk" to each other. A smooth communication among vehicles can be helpful in terms of road safety in case of sudden speed breaks, bumps, slow moving traffic, poor visibility conditions such as fog and, importantly, wrong way traffic. Our work suggests potential applications of Vehicleto-Vehicle (V2V) communication for improving road safety in Pakistan. We have considered one such unsignalized intersection point at main University Road, Karachi and presented an approach to make this road safer for vehicles and pedestrians using V2V technology.

This study aimed to investigate the effects of the splitter-island on pedestrian safety at roundabouts, considering the interaction between pedestrians and vehicles. Traffic accident statistics have traditionally been used to assess traffic safety. This method has severe limitations when used to investigate the impact of a particular feature of traffic facilities on safety at a microscopic level. Most previous research on surrogate safety measures (SSMs) had, on the other hand, focused on studying the safety of traffic operation conditions. The impact of a particular geometric feature of a roundabout on safety has so far received little attention in the literature. Therefore, we evaluated pedestrian safety in the presence and absence of physical splitter-islands by taking advantage of comparative statistical analysis (SA) and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) methods. The Towa-Cho roundabout in Nagano prefecture in Japan was chosen for this s...

There are substantial methods of degree reduction in the literature. Existing methods share some common limitations, such as lack of geometric continuity, complex computations, and one-degree reduction at a time. In this paper, an approximate geometric multidegree reduction algorithm of Wang–Ball curves is proposed. G 0 -, G 1 -, and G 2 -continuity conditions are applied in the degree reduction process to preserve the boundary control points. The general equation for high-order (G2 and above) multidegree reduction algorithms is nonlinear, and the solutions of these nonlinear systems are quite expensive. In this paper, C 1 -continuity conditions are imposed besides the G 2 -continuity conditions. While some existing methods only achieve the multidegree reduction by repeating the one-degree reduction method recursively, our proposed method achieves multidegree reduction at once. The distance between the original curve and the degree-reduced curve is measured with the L 2 -norm. Numer...

The sight distance at night is one of the most important driving safety factors. Sag vertical curves are one of the important elements of roads, which require a sufficient sight distance at night. The headlight sight distance is used for determining the length of the sag vertical curves. Presently, the parabolic curve is mainly used in symmetrical sag vertical curves. The present study aimed to propose the elliptic curve as a new alternative for the parabolic curve. An elliptic equation is developed for use in vertical curve and sight distance of the sag elliptic vertical curve in nighttime is calculated based on the characteristics of the road geometry. Results indicate that contrary to the parabolic curve, the sight distance of the elliptic curve varies depending on the vehicle location and increases as the vehicle moves forward on the curve; therefore, driver sees the end of curve in elliptic curves much earlier than parabolic curves. The results also indicate that the sight distance of the parabolic curve is more than that of the elliptic curve in the shortest length after the curve beginning (up to 8% of the curve length) while the sight distance of the elliptic curve is more than that of the parabolic curve at the rest of the curve (at least 92% of the curve length). Based on the obtained results, for S > L, the stopping sight distances of the elliptic and parabolic vertical curves are equal.

On July 1, 2005, the State of Iowa implemented a 70 mile per hour (mph) speed limit on most rural Interstates. This document reports on a study of the safety effect of this change. Changes in speeds, traffic volume on and off the rural Interstate system (diversion), and safety (crashes) for on-and off-system roads were studied. After the change, mean and 85th percentile speeds increased by about 2 mph on rural Interstates, but speeding was reduced (the number of drivers exceeding the speed limit by 10 mph decreased from 20% to about 8%). In keeping with longer term trends, volumes also increased (about 5%, which was as expected). There was no evidence of traffic shift (diversion) from off-system to on-system (rural Interstate) roads. Daytime and nighttime serious crashes were studied for a period of 14½ years prior to the change and 2½ years afterwards. Due to limitations of data, cross-median crashes were studied for 4½ years before and 2½ years after. Simple descriptive statistics reveal increases in all crash severity categories for the 2½ year period following the speed limit increase when compared to the most recent comparable 2½-year period prior to the increase. When compared to longer term trends, the increases were less pronounced in some severity levels and types, and for a few severity levels the average crash frequencies were observed to decrease. Few of the changes in crash frequency were larger than the normal year to year variation in these statistics. However, fatal and other serious cross-median crashes increased by relatively larger amounts as compared to expected random variation. Most of this increase was concentrated in the last half of 2005 and represents relatively small numbers of crashes (statistically speaking). The study also analyzed crash frequencies grouped into six-month periods, revealing similar findings. To more rigorously test for statistical significance in the findings, a generalized regression model was fit to the time series data. The model found that none of the results nor the short term trend were significant at the 95% confidence level, although several results were found to be significant at lower confidence levels.

Past roadside safety studies mostly evaluated the impact of traffic barrier geometric features using simulation tools or by conducting field crash tests. While past simulation and field crash tests could present important findings for upgrading the geometric design of traffic barriers, there is still a gap regarding conducting an actual data analysis on side traffic barriers crashes with regards to their geometric dimensions. This paper aims at filling this gap by combining a statewide dataset of side traffic barrier geometric features with historical crashes on interstate roads in Wyoming. Therefore, geometric features including system height, post-spacing, lateral offset (from the edge of pavement), and side-slope of over 150 miles of side traffic barriers were inventoried by conducting a field survey on interstate roads in Wyoming. For the statistical analysis, a random-parameters ordered logit model was utilized to investigate variables impacting crash severity of side traffic barriers. It was found that system height could significantly impact the crash severity of side box beam barriers. Box beam barriers with a system height between 25 and 31 in. were identified to be less severe in comparison to other height categories, while showing minimum risks of severe crashes in the system height of 29-31 in.. On the other hand, box beam barriers with a height taller than 31 in. may increase crash severity.

The aim of the paper is to design a grade separated intersection at Seke Road and Cripps/Dieppe Road in Harare, Zimbabwe. During the peak hours on weekdays, congestion and long queues occur at Seke Road and Cripps/Dieppe Roads intersection in Harare, Zimbabwe therefore there is need to improve this intersection. Significant traffic and congestion across urban areas creates a demand for grade separated intersections. The construction of these structures plays a critical role in the development of modern infrastructure due to safety, environmental, and economic reasons. With the increase in traffic there is need for an improved intersection. The scope of the work included an assessment of some of the intersections in Harare where grade separation is feasible, selection of one intersection, design of the grade separated intersection according to appropriate design standards and production of a bill of quantities. The project includes a traffic counting survey which was conducted for the purpose of determining the traffic volumes and hence the justification of upgrading the existing intersection. The methodology included production of a map, traffic counts, collection of secondary data on traffic counts, conducting geotechnical investigation tests and geometric and structural design of the intersection. Geotechnical investigation results were also used to determine the foundation depth of the bridge. The project contains literature of the different types of intersections, the advantages and disadvantages and also the different types of bridges. The traffic data was analysed and the most appropriate intersection design was chosen. The Simple Diamond interchange was designed because it is cost effective as it reduces congestion at Seke Road and Cripps/Dieppe Roads intersection. However the intersection should be further upgraded to a full clover leaf or a three level intersection within the next 20 years so as to avoid congestion again due to high traffic volumes. The interchange is a Simple Diamond interchange which was designed according to South African Standards. The analysis was carried out using Prokon Software, AchiCAD software, Microsoft word, AutoCAD and Microsoft word. A physical model was also made for the design. It is recommended that pre-stressed beams can be cast on the open space available and lifted by cranes to their positions and the grade separated intersection should have more columns for aesthetic reasons.

Jalan merupakan salah satu akses transportasi darat yang menghubungkan wilayah yang satu ke wilayah yang lain. Pada Ruas Jalan Trans Manado – Gorontalo yang berada pada desa Botumoputi merupakan jalan penghubung antar kota yang ada di kepulauan Sulawesi, bila dilihat secara visual pada ruas jalan ini belum memenuhi standar geometrik jalan yang dimana pada jalan ini memiliki bentuk tikungan tajam (berjari-jari kecil), yaitu kurang dari Rmin = 110 m yang dimana disyaratkan oleh Bina Marga 1997 untuk jalan Arteri (Jalan Nasional) dengan Vr = 60 km/jam. Dengan kondisi jalan seperti ini dapat menyebabkan ketidakamanan dan ketidaknyamanan bagi pengguna jalan. Penelitian dilakukan untuk mengevaluasi Geometrik Jalan pada Ruas Jalan Tans Sulawesi Manado – Gorontalo Di Desa Botumoputi Sepanjang 3 km, dikarenakan banyak tikungan yang tidak memenuhi syarat maka dilakukan perbaikan geometrik. Untuk memperoleh data kondisi geometrik lapangan maka dilakukan pengukuran menggunakan alat ukur Theodol...

This paper reviews forms of spiral geometry that have been used and proposed as transition shapes in railroad tracks and compares them with respect to dynamic performance and spiral length. The dynamic performances that are compared were calculated using the Gensys rail vehicle motion simulation program and a well known model of the Eurofima coach. The results illustrate: 1) the dynamic disturbance caused by the discontinuity of first derivatives of track curvature and twist with the conventional 'linear' spiral; 2) the better dynamic performance of other simple forms of spiral including the virtually perfect performance of two of those forms; and 3) the amounts by which lengths of alternative spirals exceed that of the conventional 'linear' spiral for the example transition..

In this paper we describe and discuss a new kernel design for geometric computation in the plane. It combines different kinds of floating-point filter techniques and a lazy evaluation scheme with the exact number types provided by LEDA allowing for efficient and exact computation with rational and algebraic geometric objects. It is the first kernel design which uses floating-point filter techniques on the level of geometric constructions. The experiments we present-partly using the CGAL framework-show a great improvement in speed andmaybe even more important for practical applications-memory consumption when dealing with more complex geometric computations.

The design and possible simplifications of four-leg channelized intersections are analysed in the paper. The research resulted in a new simpler approach in which all intersection elements are properly formed from the very beginning, so that the need for the swept path analysis and redefining of intersection elements is rendered superfluous. New procedures for the design of four-leg channelized intersections for the 60 to 90 degree intersection angles, and for semi-trailer trucks 16.5 m in length, are presented.

In previous studies, a new (improved) turboroundabout design approach based on the rules of the design vehicle movement geometry was proposed, and the optimal design of elements of standard turboroundabouts for various design vehicle scenarios, circulatory roadway radii, and approach leg positions was defined. Within the scope of this research, the applicability of the current Dutch calculation model for fastest-path vehicle speed analyses at standard turboroundabout schemes designed by a previously described procedure was examined. Research results have shown that this Dutch calculation model does not apply to standard turboroundabouts whose approach legs are aligned under various angles and translatory shifted regarding the roundabout geometric center, and therefore, should not be used for speed analyses at this roundabout type until a new calculation model, which corresponds to the real traffic situation, is developed.

Turbo roundabout is a specific kind of multilane roundabout with spiral circulatory roadway and physical separation of traffic lanes. This particular roundabout layout was developed in the Netherlands in the late nineties of the last century with the aim of solving capacity and safety problems that occur in standard multilane roundabouts. In this paper geometric design of turbo roundabouts is analysed. Comparative analysis of turbo roundabout design procedures described in the latest Croatian and source Dutch guidelines is made, modifications of Croatian turbo roundabout in regard to Dutch layout are presented, and advantages and disadvantages of both design procedures are discussed.

In the last 10 years in Croatia numerous roundabouts have been built in urban and interurban areas. As a rule, these roundabouts replaced the existing three-leg and four-leg intersection in order to increase intersection safety and capacity. Replacement of four and three-leg intersections with roundabouts was often carried out without taking into account the ranking of intersecting roads and space requirements. Because of that the capacity and safety levels on these roundabouts were often lower than those on previous four or three-leg intersections. In some cases, poor roundabout design decisions resulted in insufficient lane width on entrance and exit (offtracking control problem), inadequate intertwining lengths (on two-lane roundabouts), tangential entrances, and travel speed. These problems are particularly pronounced when the road axis do not intersect at right angle. Unfortunately, lessons learned from these bad examples weren’t adopted, and designers are continuing with poorl...

Safety in highways is one of the most important subjects in Transportation Engineering. Increasing rate of vehicles and the needs to design or geometrically modifying the highways, emphasized on the safe-designing of the roadways more than before. Between the constructive components of the highway, horizontal curves due to the more occurrences of accidents are of great importance. The American ministry of highway and transportation introduced the software IHSDM, with variant capabilities, to predict accidents. In this research, five types of curves (simple circle curve and clothoid-circle-clothoid) at different intersection angles were designed, and accident rates based on the standard specifications on each curve was predicted by using the IHSDM, and the results are compared with each other. Finally, by processing the curves of accident rates versus the curves types and intersection angle, and comparing them with each other, the necessity of using spiral curves in the highway desig...

The problem of constructing a smooth C 1 continuous planar interpolated spline curve has attracted the attention of many people working in the area of CAD/CAM and its applications such as robotics. In the present paper we propose a method for constructing a C 1 continuous planar interpolated spline using rational quadratic Bezier curve that falls within a closed boundary of straight line segments, which is most frequently used in computer graphics and geometric modelling. The rational quadratic curves are used by CAGD scientists since they do not require complex computations as other higher degree curves do. However, in practice it is desirable to approximate conic sections which cannot be represented by simple Bezier curve. Besides this, we have also presented the some useful properties of the rational quadratic Bezier

Modern roundabouts adoption has strongly increased since change of give-way to circulating traffic. From that moment onwards, the most recognized Roundabout Design Guidelines have evolved throughout the implementation of numerous studies. This paper presents the case of Argentina, as an example of a Latin American country, where Geometric Design Guidelines are not up to date. During the last decade, a considerable amount of these intersections have been built in rural surroundings and as a consequence, deficiencies in the performance become evident, especially where heavy vehicles circulation is present. The main goal of this work is to provide recommendations on modern roundabouts geometric parameters, such as appropriate turning radius and swept path widths, and help professionals create more efficient and safer designs when heavy and articulated vehicles are involved. This paper shows the modeling process in heavy trucks circulation scenarios, using minimum turning radius templat...

As many researchers have proved in recent years, it can be assumed that a consistent highway design is one which ensures successive elements coordinated in such a way as to produce harmonious and homogeneous driver performances and does not provoke unexpected events. Knowledge and practice highlights that drivers make fewer errors in the vicinity of geometric features that conform to their expectations. On this basis, the importance of identifying inconsistencies on highways and the significant contribution to road safety that this makes is emerging as an important feature in highway design. Although several techniques and models for evaluating the consistency of a design in a quantitative way have been identified and, even if some countries have implemented the design consistency concept in their road design guidelines in a mainly qualitative way, there have been only few efforts to measure actual driving behavior. The aim of this paper is to determine design inconsistencies on existing two-lane rural roads using actual driving behavior by means of field data measurements and to verify their agreement with a consistency evaluation model. Furthermore, suitable equipment and a procedure for surveying driving dynamics and driver workload have been developed. In particular driving behavior is assessed through direct measurements and parameters taken from data collected on a selected sample of test drivers using a purposely designed instrumented vehicle. The vehicle, named Driver Instrumented Vehicle Acquisition System (DIVAS), was driven under real traffic conditions on a two lane rural road. The design classes of consistency of the test courses were, also, evaluated using a well known Safety Criteria Model. Data collection and treatment procedures will be presented and data analysis and results from this first experiment will be given.

The Sukanagara-Bukanagara Road in Pagerwangi, Lembang District, West Bandung Regency, is an alternative route to the Lembang tourist area. This route is frequently used to avoid traffic congestion; however, accidents, such as vehicles failing to climb steep slopes, are frequent. This study aims to analyze, evaluate, and redesign the geometric aspects of the road, focusing on horizontal and vertical alignments, traffic signs, and road markings. The evaluation is based on the Road Geometric Design Guidelines (PDGJ) 2021 by Bina Marga and the Ministry of Transportation regulations 2014. Data is collected through field surveys and Digital Elevation Model (DEMNAS) and processed using Civil 3D software. The research results include the existing road conditions, evaluations based on standards, and redesign recommendations to enhance road safety and users' comfort.

The Sturm spirals which can be introduced as those plane curves whose curvature radius is equal to the distance from the origin are embedded into oneparameter family of curves. Explicit parametrization of the ordinary Sturmian spirals along with that of a wider family of curves are found and depicted graphically.

In general, the geometric planning of roads is done manually using drawing tools and mathematical techniques. When done manually, geometric design is complicated, time-consuming, and prone to errors. Therefore, this study will use AutoCAD Civil 3D ® . This study aims to redesign the Trans Flores road because of the frequent accidents found on curves and climbs and the current road drops on the Trans Flores road. This study will use research methods using secondary data and qualitative research methods. When designing geometric roads using AutoCAD Civil 3D ® , data from Google Maps, Google Earth, and Global Mapping is also required. This research will focus on the 3.5 km of road traffic starting from Sta 0+000 to Sta 3+500. The result of this study is that corners P1-P4 are planned with the type of Bend S-C-S. By using AutoCAD Civil 3D ® , this research can be completed quickly and accurately.

In urban agglomerations, signalized intersections are common. However, in traffic management, safety-focused strategies are often sacrificed for traffic efficiency by allowing simultaneous multiple conflicting movements. We identified this issue by analyzing the most dangerous signalized intersections in several Polish cities. Our research evaluated whether obstructed sight distances between major and minor traffic streams could be a significant problem at these intersections. To achieve this, we employed existing models of visibility analysis related to stopping sight distance. We determined the key parameter for stopping sight distance based on our vehicle speed studies. Tests were conducted using unmanned aerial vehicles over the intersections in the cities under consideration. Subsequently, we adapted available sight distance models to characterize conflicting streams with simultaneous green signals in a signal phase. We distinguished between major movements, including tram, pedestrian, and cyclist traffic, and minor streams, primarily involving turning vehicle movements at the intersection. Through this approach, we analyzed stopping sight distance and found that in about 60% of the cases studied, the obstructed sight distances led to a higher number of traffic incidents in the areas of conflict between major and minor traffic streams. The overall number of traffic incidents was more than 57% higher in areas with obstructed sight distance conditions, with the worst statistics involving incidents with vulnerable road users. This straightforward approach confirmed the findings of many studies that sight distance is one of the most critical factors influencing traffic safety. Based on our research findings, we recommend implementing safe traffic management strategies at intersections with obstructed sight distances, specifically multiphase signalization. Additionally, due to the often-necessary compromise in phases involving pedestrian and cyclist traffic, we recommend conducting required sight distance analyses for vehicles turning left or right while conflicting with pedestrian or cyclist streams during a shared signal phase. Given the simplicity of the method, further research is needed to refine the approach, possibly by incorporating a stochastic model.

The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use.

This paper compares four systems of deployable scissor-like structures (also known as double layer grid-articulated joint systems). Its aim is to understand which of these require fewer elements to cover/span a given area. The results are assessed for five cases of the same area but with different geometry. As part of the research, two different methods have been used, contrasting the precision and convenience of each one simultaneously. On the one hand, we have used mathematical equations that allow us to quantify the amount of rods and joints needed in each system. On the other hand, in carrying out these evaluations, we have also used several digital models made with Grasshopper, a software that offers us tools to create algorithms. To conclude, we then evaluate the results obtained via both procedures.