Reliability indices for road geometric design

1992 ◽  
Vol 19 (5) ◽  
pp. 760-766 ◽  
Author(s):  
Francis P. D. Navin
Keyword(s):  
Reliability Index ◽  
Design Parameters ◽  
Limit States ◽  
Highway Design ◽  
Reliability Indices ◽  
The Road ◽  
Modifying Factors ◽  
Sight Distance ◽  
Margin Of Safety ◽  
Stopping Sight Distance

Highway engineers, when asked to state the safety of a particular design, are usually at a loss to give a single meaningful measure as is possible in structural or geotechnical engineering. This paper outlines a method to estimate the margin of safety and reliability index for isolated highway components. The stopping sight distance is used to demonstrate the method. The method uses the basic highway design equations. On the assumption that the variables are random, the expected value of the mean and the variance are estimated; and from these the margin of safety and the reliability index are calculated. The most likely combination of variables for the existing design condition may also be estimated. The variables included represent the characteristics of the driver, the vehicle, and the road surface.A method is proposed to specify the design parameter's value representing a road's strategic importance, the users, the vehicles, the drivers, the environment, the terrain, and the standard of design and construction. The apparent advantage of the proposed reliability-based method is that the designer must explicitly specify the importance of the modifying factors and may also more closely investigate the behaviour of the variables in the design parameters in the critical region near noncompliance. Key words: limit states design, stopping sight distance, safety, highway design, reliability.

Coupling Impacts of Spray and Rainfall on Road Visibility and Vehicle Speeds: A Simulation-based Analysis

2021 ◽  
Author(s):  
Shuyi Wang ◽  
Tianheng Chen ◽  
Bin Yu ◽  
Yue Sun ◽  
Xiaochun Qin
Keyword(s):  
High Speed ◽  
Traffic Accidents ◽  
Water Film ◽  
Design Parameters ◽  
Vehicle Speed ◽  
Highway Design ◽  
The Road ◽  
Sight Distance ◽  
Rain Medium ◽  
Stopping Sight Distance

Impaired visibility resulting from rainfall contributes greatly to the occurrence of traffic accidents. This study presents a numerical simulation approach to analyze the extent to which the coupling of spray and raindrops reduces visibility and thus proposes safe speeds against inadequate visibility. The spray-raindrop coupling particles were modeled by considering the real highway design parameters and rainfall conditions. The road visibility was estimated through simulating the multiple scattering process of taillights in the spray-rain medium, and the maximum safe speed against inadequate visibility was then derived by comparing the visibility with the required stopping sight distance. Results show that: 1) either a high speed of the front truck or a thick water-film results in a significant reduction in road visibility and the maximum safe speed of the ego vehicle, 2) front vehicle speed plays a more important role in visibility reduction than the water-film thickness does.

Three-Dimensional, Probabilistic Highway Design

2008 ◽  
Vol 2060 (1) ◽  
pp. 10-18 ◽  
Author(s):  
Mohamed Sarhan ◽  
Yasser Hassan
Keyword(s):  
Reliability Analysis ◽  
Probabilistic Approach ◽  
Three Dimensional ◽  
Design Parameters ◽  
Horizontal Curve ◽  
Vertical Alignment ◽  
Highway Design ◽  
Side Slope ◽  
Sight Distance ◽  
Stopping Sight Distance

The potential usefulness of reliability analysis has recently been stressed in many engineering applications. Given the variability in the design parameters, a reliability-based probabilistic approach is well suited to replace the current deterministic highway design practice. However, progress in this regard is generally slow. In this study, the reliability analysis was used to estimate the probability of hazard (POH) that might result from insufficiency of sight distances. As an application, the available sight distance was checked against required stopping sight distance on an assumed road segment. Variation of the design parameters was addressed with Monte Carlo simulation using 100,000 sets of design parameters based on distributions available in the literature. A computer program was developed to use these sets of design parameters to calculate the profiles of available and required stopping sight distances in two- and three-dimensional projections as well as the profile of POH. The approach was applied to a horizontal curve overlapping with flat grade, crest curves, and sag curves in a cut section where the side slope would restrict the sightline. The analysis showed that the current deterministic approach yields very conservative estimates of available and required stopping sight distance, resulting in very low POH. The application example also showed the change of POH with the change of vertical alignment parameters.

Driver Perception–Brake Response in Stopping Sight Distance Situations

1998 ◽  
Vol 1628 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Daniel B. Fambro ◽  
Rodger J. Koppa ◽  
Dale L. Picha ◽  
Kay Fitzpatrick
Keyword(s):  
Response Time ◽  
Performance Studies ◽  
Response Times ◽  
Highway Design ◽  
Braking Performance ◽  
Reaction Distance ◽  
State Highway ◽  
Sight Distance ◽  
Design Speed ◽  
Stopping Sight Distance

One of the most important requirements in highway design is the provision of adequate stopping sight distance at every point along the roadway. At a minimum, this sight distance should be long enough to enable a vehicle traveling at or near the design speed to stop before reaching a stationary object in its path. Stopping sight distance is the sum of two components–brake reaction distance and braking distance. Brake reaction distance is based on the vehicle’s speed and the driver’s perception–brake reaction time (PBRT). Four separate, but coordinated, driver braking performance studies measured driver perception–brake response to several different stopping sight distance situations. The results from the driver braking performance studies suggest that the mean perception–brake response time to an unexpected object scenario under controlled and open road conditions is about 1.1 s. The 95th percentile perception–brake response times for these same conditions was 2.0 s. The findings from these studies are consistent with those in the literature: that is, most drivers are capable of responding to an unexpected hazard in the roadway in 2.0 s or less. Thus, the American Association of State Highway and Transportation Officials’ perception–brake response time of 2.5 s encompasses most of the driving population and is an appropriate value for highway design.

scholarly journals The Influence of Visibility Conditions in Horizontal Road Curves on the Efficiency of Noise Protection Barriers

2013 ◽  
Vol 2 (2) ◽  
pp. 22-32
Author(s):  
Tamara Džambas ◽  
Saša Ahac ◽  
Vesna Dragčević
Keyword(s):  
Minimum Distance ◽  
Noise Source ◽  
Design Parameters ◽  
Noise Barriers ◽  
Road Design ◽  
Sight Distance ◽  
Noise Barrier ◽  
Design Software ◽  
Stopping Sight Distance ◽  
Static Noise

Abstract Ensuring sufficient visibility on planned roads by sight distance testing is an integral part of every project, but problems with visibility can emerge when noise barriers are erected on existing roads. Namely, in order to provide sufficient noise protection, high noise barriers are often placed at minimum distance from the carriageway edge, and additional visibility testing in most cases is not carried out. Research described in this paper consists of stopping sight distance tests conducted by means of specialized road design software MX Road, and noise barrier optimization conducted by means of specialized noise prediction software LimA using static noise calculation method RLS 90. The aim of this research is to establish whether the required stopping sight distance on road sections where minimum design parameters are applied can be achieved if the noise barrier is placed at minimum distance from the carriageway edge, and to establish whether the optimized dimensions of planned noise protection barrier will change if the barrier is placed on larger distance from the noise source, which is, in this case, the existing road.

scholarly journals SIGHT DISTANCE ANALYSES IN ROAD DESIGN PROCESS: SERBIAN PRACTICE

Transport ◽  
2016 ◽  
Vol 31 (2) ◽  
pp. 250-259 ◽  
Author(s):  
Dejan Gavran ◽  
Sanja Fric ◽  
Vladan Ilić ◽  
Filip Trpčevski
Keyword(s):  
Cross Sections ◽  
3D Models ◽  
Software Tools ◽  
Design Parameters ◽  
Operating Speed ◽  
The Road ◽  
Road Design ◽  
Sight Distance ◽  
Road Geometry ◽  
Design Speed

New Serbian policies on road design introduce the concept of operating speeds. Decades ago, national policies were based on the constant design speed concept. Among other design parameters, in relation to that constant design speed, minimum radii of horizontal and vertical road geometry were determined. Introduction of the operating speed concept provides for more realistic prediction of speed levels along the road. Unlike the constant design speed, operating speed levels vary along the road, reaching higher levels in curves with larger radii, on straight sections and on reverse curves and dropping down to the design speed level in horizontal curves with the minimum radius. Consequently, besides a constant Stopping Sight Distance (SSD), which is calculated from the constant design speed, the new term, Required Sight Distance (RSD) is introduced. RSD varies along the road, as it is calculated from the operating speed, which also varies along the road. Appropriate RSD analyses are crucial on road rehabilitation projects, since a simple resurfacing that enables higher speed levels, without providing increased RSD, may hamper the safety of a newly resurfaced road. Software tools for predicting operating speed levels and optical analyses of the road are also presented in this paper. Software tools for RSD analyses enable the import of lines of sight into the 3D model of the roadway and their export into the cross sections extracted from the model, thus facilitating the obstacle removal. Also demonstrated are tools for determining Available Sight Distance (ASD), which are based on triangulated 3D models of the roadway as well.

scholarly journals Assessment of traffic safety at median openings using surrogate safety measures: a case study in India

2020 ◽  
Vol 80 (ET.2020) ◽  
pp. 1-12
Author(s):  
Malaya Mohanty
Keyword(s):  
Developing Countries ◽  
Traffic Safety ◽  
Transportation Engineering ◽  
Crash Data ◽  
Road Crashes ◽  
The Road ◽  
Sight Distance ◽  
Traffic Volumes ◽  
Road Crash ◽  
Stopping Sight Distance

Traffic safety is an integral part of transportation engineering. In developing countries, its importance is even more. Additionally, at uncontrolled median openings, the severity of road crashes increase many fold. Conventionally, road crash data were used to analyse safety. However, in developing countries, the accuracy of this data is highly questionable. Therefore, in this study, a new technique in addition to post encroachment time (PET), which is a surrogate safety measure is used to predict the severity of probable road crashes at median openings. After the extraction of PET values from field data, they have been compared with the minimum braking times obtained from calculation of minimum stopping sight distance. The comparison shows that while the number of road crashes may be less at lower traffic volume levels, however the severity of those crashes is much higher as compared to the road crashes occurring at high traffic volumes.

scholarly journals Building an Integrated Database of Road Design Elements

2020 ◽  
Author(s):  
Ali Dhafer Abed
Keyword(s):  
Road Network ◽  
Design Elements ◽  
Northern Iraq ◽  
The Road ◽  
Sight Distance ◽  
Sensing Technology ◽  
Design Speed ◽  
Stopping Sight Distance ◽  
City Structure ◽  
The City

The road network is the main artery within the city structure, which requires designing of routes and classification within the standards. Hence, the importance of this chapter, which will focus on the standards and design elements of the engineering design of road in terms of road type system, functional classification system, traffic volume system, number of traffic lane system, road width design, side slopes and elevations of road layers, super elevation, design speed, overtaking and stopping sight distance, longitudinal and cross sections of the road path, design elements of horizontal and vertical curves, and intersections. The Civil 3D Land Desktop, GIS programs, and remote sensing technology will be used to design the path of major highway linking two urban areas in Mosul (Northern Iraq), which will be considered a case study. The path of the road and its elements will be designed according to special criteria that are compatible with the topography and nature of the area. The geometric data of the road will then be exported with all the design elements to the GIS program to build an integrated road database. The database is capable of spatial analysis and connectivity with other parts of the road network in the city.

scholarly journals Reliability of stopping and decision sight distance at roundabouts

2021 ◽  
Author(s):  
Jafar Faizi
Keyword(s):  
Probabilistic Method ◽  
Design Parameters ◽  
Second Moment ◽  
First Order ◽  
State Highway ◽  
Sight Distance ◽  
Design Variables ◽  
First Order Second Moment ◽  
Stopping Sight Distance ◽  
Lateral Clearance

The existing Stopping Sight Distance (SSD) and Decision Sight Distance (DSD) design methods for roundabouts are deterministic. This means that all of the design variables are predetermined, fixed values. This study presents a probabilistic method for the determination of SSD and DSD at roundabouts based on the equation recommended by the American Association of State Highway and Transportation Officials (AASHTO 2011). The reliability-based method considers all design parameters as random variables. Three types of SSD (SSD for approaches, SSD along the circulatory lane, and SSD for exiting vehicles to the pedestrian crosswalk) were considered in this study. DSD was considered for roundabout approaches. The First-Order Second-Moment and Advanced First-Order Second-Moment methods were used to model SSD and DSD. Once the required SSD and DSD were determined, the lateral clearance requirements at every point of the roundabout were calculated.

scholarly journals PENINGKATAN KESELAMATAN DI RUAS JALAN PANTURA KM 46–47 KECAMATAN PATROL KABUPATEN INDRAMAYU

2021 ◽  
Vol 21 (2) ◽  
pp. 101-108
Author(s):  
Arivia Shehera Kurniastuti ◽  
Novita Sari ◽  
Sulistyo Sutanto
Keyword(s):  
Traffic Safety ◽  
Traffic Accidents ◽  
North Coast ◽  
Traffic Signs ◽  
The Road ◽  
The North ◽  
Road Section ◽  
Sight Distance ◽  
Speed Management ◽  
Stopping Sight Distance

Abstract   The number of traffic accidents that occur in Indramayu Regency continues to increase and causes many casualties and material losses. From the available data, it is known that there is one road section which is an accident-prone area, namely the North Coast Java Road section, KM 46-47, which is located in Patrol District, Indramayu Regency. The flow and speed of traffic on this road is quite high, because of its function as a primary arterial road. This study aims to improve safety on the North Coast Java Road section, KM 46-47. The method used is in the form of observation and field data collection. Furthermore, the data obtained is processed, analyzed, and followed by formulating appropriate recommendations. This study shows that the main cause of accidents is the human factor, especially those related to high traffic speeds. To improve the existing conditions, it is proposed to provide road equipment, especially traffic signs, which are adjusted to the stopping sight distance required by motorized vehicles using the road. In addition, it is necessary to apply speed management as part of efforts to improve traffic safety.   Keywords: traffic accident; stopping sight distance; road equipment, traffic speed; traffic signs.     Abstrak   Angka kecelakaan lalu lintas yang terjadi di Kabupaten Indramayu terus meningkat dan menyebabkan banyak korban jiwa dan kerugian material. Dari data yang ada diketahui bahwa terdapat satu ruas jalan yang termasuk daerah rawan kecelakaan, yaitu ruas Jalan Pantai Utara Jawa, KM 46-47, yang terletak di Kecamatan Patrol, Kabupaten Indramayu. Arus dan kecepatan lalu lintas di ruas jalan tersebut cukup tinggi, karena fungsinya sebagai jalan arteri primer. Studi ini bertujuan untuk meningkatkan keselamatan di ruas Jalan Pantai Utara Jawa KM 46-47. Metode yang digunakan berupa observasi dan pengumpulan data lapangan. Selanjutnya data yang diperoleh diolah, dianalisis, kemudian dirumuskan rekomendasi yang tepat. Studi ini menunjukkan bahwa faktor penyebab kecelakaan yang utama adalah faktor manusia, khususnya yang berhubungan dengan kecepatan lalu lintas yang tinggi. Untuk memperbaiki kondisi yang ada, diusulkan pemberian perlengkapan jalan, khususnya rambu lalu lintas, yang disesuaikan dengan jarak pandang henti yang diperlukan oleh kendaraan bermotor yang melintasi jalan tersebut. Selain itu perlu diterapkan manajemen kecepatan sebagai bagian upaya meningkatkan keselamatan lalu lintas.   Kata-kata kunci: kecelakaan lalu lintas; jarak pandang henti; perlengkapan jalan, kecepatan lalu lintas; rambu lalu lintas.

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