scholarly journals Evaluation of design consistency on horizontal curves for two-lane state roads in terms of vehicle path radius and speed

2016 ◽  
Vol 11 (2) ◽  
pp. 127-135
Author(s):  
Biljana Maljković ◽  
Dražen Cvitanić
Keyword(s):  
Horizontal Curves ◽  
Percentage Difference ◽  
Friction Factors ◽  
The Difference ◽  
Design Speed ◽  
Vehicle Path ◽  
Design Consistency ◽  
Side Friction ◽  
Curve Radius ◽  
The Impact

Experimental investigation was conducted on a 24 km long segment of the two-lane state road to collect the driver behavior data. The research involved 20 drivers driving their own cars equipped with the GPS device. Considering the impact of path radius and speed on the side friction demand, the design consistency on horizontal curves was evaluated by determining the margins of safety. The analysis showed that the vehicle path radii were mainly smaller than curve radius, on average for 12%. Regression analysis indicated that the percentage difference between the curve radius and vehicle path radius is not affected by the speed, speed differential and geometric characteristics of the curve and surrounding elements. Two different margins of safety were analyzed. One is the difference between maximum permissible side friction (based on design speed) and side friction demand, while another is the difference between side friction supply (based on operating speed) and side friction demand. Generally, demands exceeded supply side friction factors on curves with radii smaller than 150 m, whereas “poor” conditions (in terms of Lamm’s consistency levels) were noted for curves under approximately 220 m. Both values are very close to the critical radius below which higher accident rates were observed according to several accident studies. Based on the results of the research, it is proposed to use a 12% smaller curve radius for the evaluation of margin of safety and that curves with radii smaller than 200 m should be avoided on two-lane state roads outside the built-up area.

Effect of speed prediction models and perceived radius on design consistency

2005 ◽  
Vol 32 (2) ◽  
pp. 388-399 ◽  
Author(s):  
Laurel Richl ◽  
Tarek Sayed
Keyword(s):  
Prediction Models ◽  
Operating Speed ◽  
The Road ◽  
Speed Prediction ◽  
The Difference ◽  
Design Speed ◽  
Design Consistency ◽  
Side Friction ◽  
Consistency Evaluation ◽  
Selection Of

The most frequently used criteria to evaluate design consistency are the difference between design speed and operating speed, operating speeds on successive elements, and assumed side friction of the road and that demanded by the driver. The operating speed, often obtained using speed prediction models, influences each design consistency criteria. There has been considerable research in developing design consistency measures and evaluation tools, but little research has been done on the influence that different speed prediction models have on design consistency criteria. In addition, there has been little research as to how design factors such as driver perception of combined horizontal and vertical curves influence speed prediction models. This paper investigates how the selection of speed prediction models and driver perception of combined horizontal and vertical curves influence design consistency evaluation. The selection of the speed prediction model has a significant impact on design consistency evaluation. The use of perceived radius, which accounts for driver perception of combined alignments, slightly influenced the outcome of the design consistency evaluation.Key words: design consistency, speed prediction models, driver perception, combined horizontal and vertical curves, perceived radius, geometric design.

Design radius requirements for simple horizontal curves on three-dimensional alignments

2003 ◽  
Vol 30 (6) ◽  
pp. 1022-1033 ◽  
Author(s):  
Said M Easa ◽  
Essam Dabbour
Keyword(s):  
Three Dimensional ◽  
Design Guidelines ◽  
Comfort Level ◽  
Vertical Alignment ◽  
Passenger Cars ◽  
Minimum Radius ◽  
Horizontal Curves ◽  
Design Speed ◽  
Side Friction ◽  
Mathematical Relationships

Current North American design guides have established mathematical relationships to calculate the minimum radius required for horizontal curves as a function of design speed, maximum superelevation, and maximum side friction. For three-dimensional (3-D) alignments, the design guides consider the alignment as two separate horizontal and vertical alignments and consequently ignore the effect of vertical alignment. This paper evaluates the effect of vertical alignment on minimum radius requirements using computer simulation, with a focus on trucks. For 3-D alignments, the results showed that existing design guidelines for minimum radius need to be increased by as much as 20% to achieve the same comfort limit on flat horizontal curves. It is interesting to note that in some cases truck rollover occurred before the side-friction comfort level is reached. This indicates the need for developing a different design control for trucks on 3-D alignments than the comfort criterion used for passenger cars on flat horizontal curves. Based on the simulation results, mathematical models for design radius requirements for passenger cars and trucks were developed.Key words: geometric design, horizontal curve radius, three-dimensional alignments, vehicle stability.

scholarly journals Geometric design of single-lane roundabouts for optimum consistency and operation

2021 ◽  
Author(s):  
Atif Mehmood
Keyword(s):  
Optimum Design ◽  
Optimization Model ◽  
Operational Performance ◽  
Design Parameters ◽  
Operating Speed ◽  
Site Conditions ◽  
Design Speed ◽  
Vehicle Path ◽  
Design Consistency ◽  
Geometric Layout

The objectives while designing roundabout is design consistency and operational performance. Design consistency affects roundabout safety while operational performance affects its level of service. Along with design consistency, roundabout will be more safe if its geometry forces traffic to enter and circulate at less than specified design speed. Vehicle path radii control speeds at each vehicle path. Vehicle path radii are traditionally obtained from drawing freehand each vehicle paths on proposed roundabout geometry. Existing design approaches for roundabouts use a trial-and-error procedure to choose the design parameters in order to satisfy design standards. With this approach it is quite complicated to satisfy design guidelines and site conditions at the same time. A minor change in geometry can result in significant changes in safety and operational performance. Therefore, many iterations of geometric layout would be required to evaluate safety and operational analysis at given traffic conditions. Designer needs to revise and refine the initial geometric layout to enhance safety and its operational performance. In this thesis, an optimization model is developed that predicts optimum design parameters with multiple objectives: maximum design consistency and minimum average intersection delay. At optimum design parameters, this model also provides vehicle path radii for each path. These vehicle path radii were used to predict operating speed along each path using an existing operating speed prediction model. The optimization model takes site conditions as input and satisfies the two objectives for given traffic and geometric conditions. This is a new approach of optimum design of single-lane roundabouts with four legs intersecting at right angle. The model not only satisfies the two objectives, but also limits the operating speed along each path (left, through, and right), below the specified design speed of roundabout.

scholarly journals Assessing the Impact of Government Initiatives on Reducing Poverty amongst Women at Professor Dora Akunyili Women Development Centre in Anambra State, Nigeria

2020 ◽  
Vol 5 (3) ◽  
pp. 1462-1469
Author(s):  
Onugu Charles U ◽  
Anumudu Oluchi O ◽  
Obianefo Chukwujekwu A
Keyword(s):  
Poverty Reduction ◽  
Anambra State ◽  
Development Centre ◽  
Percentage Difference ◽  
Before And After ◽  
Poverty Status ◽  
Household Assets ◽  
The Difference ◽  
Materials Used ◽  
The Impact

The study examined the impact of Government Initiatives of reducing poverty amongst women in Anambra state based on a case study of Professor Dora Akunyili Women Development centre. The paper focused on the activities of the centre in championing poverty reduction among women. A wellstructured questionnaire was used to elicit information from randomly selected 112 trainees for the study. Descriptive statistics such as frequency, percentage and mean were used. Percentage difference was equally used to ascertain the difference in poverty status of women before and after the training. The study showed that the trainees had mean income of N50,405.56 and N151,338.89 before and after the training; mean savings before and after the training was N35,741.11 and N48,150.00; mean expenditure on household food was N21,266.67 and N38,111.11 before and after the training; mean expenditure on household health before and after the training was ₦26,000.00 and ₦28,927.78, while mean expenditure on household assets acquisition before and after the training was ₦27,811.11 and ₦55,075.00 respectively. The major challenges faced by the trainees were administrative bottlenecks and bureaucracy in the release of capital funds, late arrival of materials used for the training, among others.

scholarly journals KELIO TRASOS HORIZONTALIŲJŲ KREIVIŲ ĮTAKA TRANSPORTO SRAUTO GREIČIUI / INFLUENCE OF ROAD ALIGNMENT HORIZONTAL CURVE ON TRANSPORT FLOW OPERATING SPEED

2019 ◽  
Vol 11 (0) ◽  
pp. 1-7
Author(s):  
Mindaugas Šeporaitis ◽  
Viktoras Vorobjovas
Keyword(s):  
Road Network ◽  
Operating Speed ◽  
Horizontal Curve ◽  
The Road ◽  
Horizontal Curves ◽  
Legal Documents ◽  
Transport Flow ◽  
Design Speed ◽  
Side Friction ◽  
Curve Selection

Geometric parameters of road alignment are fundamental elements defining permissible speed and vice versa. Unlike permissible speed, determined operating speed in upgrade projects has a significant impact on the safe movement of transport on the roads. The article reviews the composition of the regional road network in Lithuania, the design speed, the permitted speed, the practical problems of applying the geometry parameters of the road alignment according to the legal documents valid in Lithuania, methods of horizontal curve selection in Lithuania and other countries are analysed in more detail. Comparative initial calculations of horizontal curves were performed using different side friction coefficients. Review summary of analysis conducted and statements are prepared for discussion.

Evaluation of design consistency on horizontal curves for two-lane state roads using bicycle-model and realistic parameters of driver behaviour

2021 ◽  
Author(s):  
◽  
Biljana Maljković
Keyword(s):  
Point Mass ◽  
Horizontal Curve ◽  
Vehicle Model ◽  
Mass Model ◽  
Driver Behaviour ◽  
Horizontal Alignment ◽  
Horizontal Curves ◽  
Road Design ◽  
Vehicle Path ◽  
Design Consistency

The loss of vehicle stability in horizontal curves is a clear indicator of horizontal alignment design inconsistency, which can easily be quantified by determining the margins of safety. The doctoral thesis presents an overview of current horizontal alignment design guidelines and most important research of the design consistency concept. The following significant shortcomings in current road design practice were noticed: selection of unrealistic relevant speeds, the assumption that drivers follow a path with a radius equal to curve radius and the application of too simple vehicle model, i.e. basic point mass model. To overcome the observed limitations, the new consistent design approach has been developed, with an emphasis on horizontal curves. The new approach is based on the margin of safety concept, improved in terms of using the bicycle vehicle model in combination with more realistic values of speed and vehicle path radii. The bicycle vehicle model considers longitudinal load transfer, on individual axles, due to grade and speed changes, i.e. factors affecting margins of safety that are completely ignored by the simple point mass model used so far. To collect the driver behaviour data, an experimental investigation was conducted on a segment of the two-lane state road DC1 (Croatia). Individual speeds and vehicle path radii achieved by representative sample of drivers were recorded with a highfrequency GPS device. Based on the analysis of recorded data, the implementation of naturalistic driver behaviour in the road design process is proposed through regression models for predicting operating speeds (for tangents and horizontal curves) and through the equation for calculating the critical path radius. The improvement of the safety margin concept has created the basis for designing horizontal curves with high level of safety, both for the values of available friction on modern pavements as well as for future measurements. Based on operating speed consistency criterion and improved safety criterion related to driving dynamic consistency, the graphs of applicable adjacent horizontal curve radii were developed. The results obtained showed that the values of minimum horizontal curve radii need to be increased and, finally, this analysis has provided a physical explanation of the most common causes of accidents in sharp horizontal curves.

Study on Road Geometric Alignment Parameters Based on Vehicle Handling Stability Simulation

2013 ◽  
Vol 404 ◽  
pp. 273-279
Author(s):  
Xue Lian Zheng ◽  
Xian Sheng Li ◽  
Cheng Wu Jiao ◽  
Gang Bai ◽  
Yuan Yuan Ren
Keyword(s):  
High Speed ◽  
Degrees Of Freedom ◽  
Negative Influence ◽  
Vehicle Dynamic ◽  
Vehicle Handling ◽  
Horizontal Curves ◽  
Research Achievement ◽  
Vehicle Dynamic Model ◽  
Curve Radius ◽  
The Impact

Unreasonable road geometric alignment has a negative influence on vehicle handling stability, especially when vehicle drives with a high speed. For horizontal road alignment, radius and banking of circular curve are the most popular and important parameters. To investigate the influence of horizontal road alignment on vehicle handling stability, a 3 degrees-of-freedom vehicle dynamic model is established. Three road horizontal curves with different radius are established in Carsim environment to investigate the influence of curve radius on vehicle handling stability and four different banking curve roads are built to study the impact of road banking on vehicle roll stability. The research achievement will provide theoretical basis and technical support for road geometric alignment design.

Driving Dynamic Aspects and Related Safety Issues for Modern Geometric Design of Non-Built-Up Roads

1996 ◽  
Vol 1523 (1) ◽  
pp. 34-45
Author(s):  
Ruediger Lamm ◽  
Basil Psarianos ◽  
George Soilemezoglou ◽  
George Kanellaidis
Keyword(s):  
Geometric Design ◽  
Driving Dynamic ◽  
Safety Criterion ◽  
Rural Roads ◽  
Safety Issues ◽  
Road Design ◽  
Friction Factors ◽  
The Status ◽  
Design Consistency ◽  
Side Friction

Safety issues affecting modern highway geometric design of roads in non-built-up areas are discussed. The status of knowledge of Safety Criteria I and II (achieving operating speed consistency and design consistency) for two-lane rural roads is briefly reviewed. Considerations for design consistency are also extended to multiple-lane rural and suburban road design to evaluate good, fair, and poor design levels for these road categories. Utilization ratios (n) for maximum permissible side friction factors are developed for different road categories, topography levels, and maximum and minimum superelevation rates. Relevant minimum radii for curve design are established and compared with present AASHTO values insofar as possible. Safety Criterion III (achieving driving dynamic consistency) is further developed, through which reliable and quantitative ranges between the side friction assumed and the actual friction demand at curved sites could be established. AASHTO's design policy is evaluated on the basis of Criteria II and III. The evaluation showed, for lower design speeds (30, 40, and 50 mph), an unbalanced degree of curve and superelevation rate ranges, which lead to poor design practices from a safety viewpoint. By heeding the three safety criteria and the recommended side-friction utilization ratios, sound alignments can be established for the various design cases in future highway geometric design and redesign and for resurfacing, restoration, and rehabilitation strategies.

Safety Evaluation of Geometric Design Criteria: Horizontal Curve Radius and Side Friction Demand on Rural, Two-Lane Highways

2019 ◽  
Vol 2673 (3) ◽  
pp. 516-525
Author(s):  
Scott Himes ◽  
Richard J. Porter ◽  
Ian Hamilton ◽  
Eric Donnell
Keyword(s):  
Negative Binomial ◽  
Negative Binomial Regression ◽  
Geometric Design ◽  
Design Criteria ◽  
Speed Limit ◽  
Horizontal Curve ◽  
Mass Model ◽  
Design Speed ◽  
Side Friction ◽  
Curve Radius

AASHTO’s A Policy on Geometric Design of Highways and Streets, 6th Edition, provides design criteria for horizontal curve elements based on the point-mass model. The model equates the centripetal force needed to navigate a horizontal curve of a specific radius traveling at the design speed to the combination of superelevation rate and side friction needed to achieve that force. Few researchers have examined the safety impacts of horizontal curve radius, superelevation rate, and design speed through crash-based research. None of the research reviewed included the effects of design speed or superelevation rate in the crash modification factors (CMFs) or functions. This research explored these factors using a negative binomial regression modeling approach based on data collected from the SHRP 2 RID 2.0 for 889 horizontal curves on rural two-lane highways in Indiana and Pennsylvania, which resulted in roadway departure crash modification functions for horizontal curve radius and side friction demand. The crash modification function for side friction demand includes an interactive component of horizontal curve radius and speed and a direct effect of superelevation rate on roadway departure crashes. The results showed that roadway departure crashes are expected to increase for decreasing curve radius, increasing posted speed limit, and decreased superelevation rate. Furthermore, curve-related CMFs were sensitive to the curve radii used in their development. CMFs developed from curves with larger radii tended to result in larger CMFs. Sample applications are provided for computing the effects of changing the horizontal curve radius, posted speed limit, or both on proposed alternatives.

Comparison of Collisions of Rigid Trucks and Articulated Trucks Against Road Safety Barriers

2001 ◽  
Vol 1779 (1) ◽  
pp. 141-149
Author(s):  
Vittorio Giavotto ◽  
Mariano Pernetti
Keyword(s):  
Road Transport ◽  
Second Phase ◽  
Heavy Vehicles ◽  
Third Phase ◽  
Safety Barriers ◽  
Suspension Stiffness ◽  
The Difference ◽  
Side Friction ◽  
The Impact ◽  
Analytical Expressions

Heavy vehicles used for road transport are essentially rigid trucks, rigid trucks with trailers, and articulated trucks. A collision of such a vehicle against a safety barrier has different outcomes, depending on the vehicle characteristics, even when the impact energy (Ie) is the same. The factors responsible for the different behavior of rigid and articulated trucks during collision are addressed. The study, carried out by computer simulation, was divided into three parts. The first part compared the overall behavior of the two types of vehicles during collisions to detect the most responsible factors. In the second phase, the single features that characterize each type of vehicle were tested. The third phase tried to define a relationship between the two types of vehicles. Results from Tests TB81 and TB71, established by the European Committee for Standardization 1317, were compared. The results show that a collision of an articulated truck is less severe than one of a rigid truck because of greater length, suspension stiffness, inertia, and configuration. However, the difference in behavior depends on kinetic Ie and side-friction coefficient (SFC). Four analytical expressions were found that relate Ies producing the same maximum transversal displacements or vehicle roll angle for the two types of vehicles. The study concerning the European tests on safety barriers shows that a hierarchy exists between them and it depends on the SFC.

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